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[Introduction] With the development of wind power generation technology, the unit capacity of permanent magnet wind generator is increasing, and the heating power is also increasing. The heat dissipation of generator is facing unprecedented challenges. How to effectively solve the problem of generator temperature rise and heat dissipation difficulty has been the focus of our study. [Method] Based on the STAR-CCM+ software platform, an integrated numerical simulation method for generator heat dissipation and cooling was proposed in this paper. The reliability of the numerical calculation method was verified by comparing the calculated values with the experimental values. On this basis, a study was conducted on the internal temperature distribution law and the factors influencing the cooling system heat dissipation performance of the high power permanent magnet wind generator. [Result] Under the rated power, the highest temperature of the winding and stator core appear in the middle area. If the process conditions allow, the cooling water pipe should be as close to the winding as possible to take away more heat. The stator core temperature and winding temperature can be reduced significantly by increasing the total intake air volume of the generator. The intake air temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake air temperature, the maximum temperature will be reduced by about 1.4℃. Reducing the intake air temperature can improve the heat dissipation performance of the generator to a certain extent. The intake water temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake water temperature, the maximum temperature will be reduced by about 3.3℃. Reducing the intake water temperature can greatly improve the heat dissipation performance of the generator. In addition, the gap between the cooling water pipe and the stator core greatly hinders the heat transfer of the cooling water pipe. Filling the gap with materials with good thermal conductivity can effectively improve the heat dissipation performance of the generator. [Conclusion] The conclusions drawn in this paper can effectively guide the heat dissipation design of permanent magnet wind generator and ensure the safe operation of wind turbines in normal work.

The study of the transient electromagnetic detection device with small sized coil and easy installation underground will offer new insights into the real-time dynamic exploration and forecast water-bearing structure in excavation roadway.By drawing on the full-space transient electromagnetic theory, this paper adopted the three-dimensional time-domain finite element method for numerical simulation to explore the characteristics of the secondary field response obtained by small coil excitation and the transient electromagnetic response received by the magnetic core coil.This study constructed a geological-geophysical model of the water-bearing fault in front of the roadway excavation working face, studied the transient electromagnetic response characteristics of the small coil device for the water-bearing fault, and compared the effects of small coil and conventional coil in advance detection.The study shows that : ①the decay law of the induced electric potential generated by the small coil source excitation is the same as that of the induced electric potential generated by the conventional transmitting coil with time, ②the magnetic core coil can effectively improve the induced signal strength, ③the application of both the small coil device and the conventional coil device can effectively explain the distribution range of the low resistance area, ④the detection results match the verification results of the roadway excavation.Combined with the underground field test, this paper verified the applicability and effectiveness of the small coil device applied to mine transient electromagnetic method advance detection.

ObjectivesThis papers aims to analyze the impact resistance of honeycomb structure with different Poisson's ratio. MethodsBased on the explicit dynamic finite element method, this paper analyzes the dynamic mechanical properties of honeycomb structures with different Poisson's ratios under in-plane impact load, and explores the influence laws of Poisson's ratios on their impact resistance. Three typical honeycomb structures with negative/zero/positive Poisson's ratios (reentrant hexagon, hexagon and semi-reentrant hexagon) are selected, their geometric parameters are changed to give them the same relative density and different Poisson's ratios (−2.76 – +3.63), and their dynamic mechanical properties under low/medium/high-speed dynamic displacement loads are analyzed. ResultsThe results show that the zero Poisson's ratio semi-reentrant honeycomb structure has the best structural stability without transverse deformation under compression deformation; without structural instability, the platform stress has little correlation with the Poisson's ratio; and the compact strain and total energy absorbtion increases with the absolute value of the Poisson's ratio. Negative Poisson's ratio honeycomb structures with large t/l and small θ are suitable for applications with high platform stress (strong deformation resistance), and negative Poisson's ratio honeycomb structures with small t/l and small θ are suitable for high total energy absorbtion applications, while zero Poisson's ratio semi-reentrant honeycomb structures are suitable for applications with high platform stress (strong deformation resistance). ConclusionsThis study can provide references for the type selection and geometric parameter design of side impact honeycomb structures.

The purification effect of coal mine groundwater reservoir on mine water mainly lies in the water-rock coupling between the rock mass and mine water.This paper systematically reviews the research methods of water-rock coupling in coal mine underground reservoirs, and presents the characterization methods of water quality and physicochemical properties of rock samples.It employs static simulation, dynamic leaching, cycle purification simulation and other tests to explore the purification regulation of mine water in coal mine underground reservoir, uses numerical simulation to obtain the selective adsorption trend of ions in the reaction process, and combines Piper three-line diagram, Gibbs model and correlation analysis to reveal the mechanism of water-rock coupling.The purification effect and research progress of suspended solids, specific ions and organic matter in coal mine underground reservoirs are discussed.The paper shows that underground reservoir of coal mine has a certain purification effect on mine water, and the purification effect of specific ions is mainly related to filtration and adsorption.Three research directions of coal mine underground reservoir purification technology in the future are proposed: ①developing large-scale and low-cost treatment technologies for underground mine water based on water-rock coupling purification, ②developing a "three-in-one" water quality control technology for coal mine underground reservoirs coupled with multiple water treatment technologies, and ③exploring the underground storage and resource utilization technology of concentrated salt wastewater for the future studies of water-rock coupling.

ObjectiveThe purpose of this paper is to explores the water-entry slamming load distribution of a trimaran connecting bridge.MethodsBased on OpenFOAM open source software and starting with the continuity equation and N-S equation, this paper establishes a free entry slamming numerical model of a trimaran connecting bridge. The dynamic changes of velocity, slamming pressure and free surface during the free entry slamming process of the trimaran connecting bridge are simulated. The convergence analysis of the grid is carried out, and the numerical solution is compared with the experimental solution to verify the accuracy of the numerical calculation method. ResultsThe results show that this method can effectively predict the falling body slamming load of a trimaran connecting bridge structure. It is found that the slamming pressure coefficient of the connecting bridge is largest near the outer corner. The peak value of the slamming pressure on the lower surface of the connecting bridge and the relationship between the slamming pressure coefficient and velocity are then obtained.ConclusionsThis study presents the characteristics and range of slamming pressure on a trimaran connecting bridge, providing a numerical basis for the structural strength evaluation and design of trimarans.

ObjectiveThe exhaust ejection device is an important part of a ship's gas turbine intake and exhaust system. It is very important to ensure the exhaust and ejection performance of the exhaust ejection device for the normal operation of the ship. MethodsAccording to the characteristics of this type of gas turbine exhaust ejection device, this paper selects eight relevant structural parameters and two objective functions in order to analyze the parameter correlation, and determines the two design variables that have the greatest correlation with the objective function. On this basis, the design parameters are optimized based on the multi-objective optimization genetic algorithm NSGA-II, and the selected optimization scheme is applied to a gas turbine intake and exhaust system assembly model for verification. Results The results show that, compared with the original scheme, the optimized exhaust ejection device has a significantly improved ejection flow rate of the gas turbine casing, meeting the design requirements of the exhaust ejection amount, but this also leads to an increase in exhaust back pressure. ConclusionThe research approaches and results obtained in this paper have certain reference value for the design and optimization of gas turbine exhaust ejection devices.

The power system of heat pipe cooled nuclear reactor can be divided into dynamic conversion system and static conversion system. Thermoelectric generator (TEG) is a typical static conversion device, which can directly convert heat energy into electric energy. The combination of heat pipe cooled nuclear reactor and TEGs can bring many advantages, such as compact structure, high inherent safety, no auxiliary mechanical equipment and low noise. However, the maximum core temperature could exceed 1 000 K, and ordinary thermoelectric generators can not operate in such high temperature. To solve this problem, the use of segmented thermoelectric generator (STEG) in the power system of heat pipe cooled nuclear reactor is a method worthy of research. STEG can play an important role in the heat pipe cooled nuclear reactor. But there is not enough literature to study the application of STEG in heat pipe cooled nuclear reactor. STEG usually splices two or three thermoelectric materials with the highest power generation efficiency in different temperature ranges. In this way, STEG can obtain a high thermoelectric conversion efficiency in a wide temperature range (usually above 600 K). Therefore, a kind of STEG for heat pipe cooled nuclear reactor was designed. In this paper, a conceptual design of a heat pipe cooled nuclear reactor with STEGs was proposed. The single STEG and single channel model were explored by COMSOL software. A three-dimensional finite element model of STEG’s performance in heat pipe cooled nuclear reactor was established. STEG was designed to compose of bismuth telluride and skutterudite, and its geometric structure and performances were optimized. Numerical simulation was carried out under steady-state conditions to determine the optimal STEG’s geometry. Then, the optimized STEG was connected with the heat pipe to form a single channel model for simulation to explore its performances. When the temperature difference reaches 550 K, the maximum STEGs’ output power reaches 0.374 W, and the maximum conversion efficiency is 15.75%. In single channel model, when the heating power is 300 W, the maximum STEGs’ output power reaches 47.29 W, and the maximum conversion efficiency is 15.63%. The simulation also show that the maximum stress of single STEG and single channel model are 270 MPa and 547.5 MPa, respectively. And the maximum stress appears on the copper conductor near the hot side. This paper could provide a preliminary basis for the numerical simulation of the combination of STEG and heat pipe cooled nuclear reactor. This paper can also be used as a reference for the thermoelectric conversion of heat pipe cooled nuclear reactors.

ObjectiveThis paper aims to explore the hydrodynamic characteristics of underwater vehicles under the action of internal solitary waves.MethodsBased on the internal solitary wave mKdV theory under the strong stratification assumption, the incompressible Navier-Stokes （N-S） equation is discretized by the finite volume method. Combining the velocity entrance wave-making and overset grid methods, a numerical model of an underwater vehicle coupled with internal solitary waves in stratified flow is established. Through this model, the coupling process of internal solitary waves and fixed and suspended vehicles in different internal wave environments is simulated, and the variation law of the hydrodynamic load is obtained by numerical solution. ResultsThe amplitude of the force and moment of the underwater vehicle increases with the increase in wave amplitude. When the position of the fixed vehicle is close to the interface of two layers of fluid, it is more severely affected. When the suspended vehicle is close to the wave trough, the impact is more significant. The increase in the initial pitch angle will lead to a sharp increase in the horizontal force amplitude of the vehicle. In addition, the "falling depth" phenomenon occurs when a vehicle with initial speed is affected by the main wave and coda wave of an internal solitary wave.ConclusionThe results obtained in this paper have reference value for safe operation of underwater vehicles.

The third generation reactors have characteristics of safety and efficiency, and the C-shaped heat exchanger is the main equipment in the design of the third generation reactor, which is widely used in the design of the passive residual heat removal system. It is of great significance on reactor safety to study on the flow and heat transfer process of Cshaped heat exchanger. To study the coupling flow and heat transfer characteristics of its primary and secondary side, and also to obtain flow distribution mechanism in heat exchange pipes for optimizing structure design, a fullsize physical model of Cshaped heat exchanger was established in this paper. It included inletoutlethousings, inletoutlet pipes and 500 heat transfer pipes as the primary side, and the heat transfer model of the secondary side was also established. Numerical simulation studies under different thermal and geometric conditions were conducted by the software FLUENT to obtain the laws of temperature, speed, pressure and flow distribution between the heat transfer tubes in primary side. At the same time, the influence of inlet flow, inlet temperature, inlet position to the flow distribution and flow resistance distribution was analyzed, and the affecting mechanism of floating force and inertial force on flow distribution was also analyzed. The calculation results show that the current design of the heat transfer tube is uneven in flow distribution, the flow of inner side is low, the flow of outer side is high, and the inner layer has the phenomenon of reverse flow. The uneven flow distribution in the current design is mainly caused by thermosiphon (density difference causing gravity pressure difference). This phenomenon is more obvious when inlet flow is low or the inlet temperature is high. During the range of the thermal parameters in this paper, the phenomenon of the thermosiphon is always dominated in the influencing mechanisms of flow distribution. Three inlet pipe positions of 0° (existing design), 90° and 180° were compared and it is found that the position of the inlet pipeline is not obvious for flow unevenness. When the flow is low, the flow distribution unevenness of the existing design (overentering and downout) is optimal on the contrary. In further study, it is possible to explore measures to reduce flow distribution unevenness. The measures include changing the connection of the heat transfer tubes and the headers, changing the distribution of the heat transfer coefficient of the primary and secondary side, and changing the installation method of the inlet headers, etc.

ObjectiveIn order to accurately assess the ice resistance experienced by an icebreaker during continuous icebreaking when sailing in a level ice zone, and understand the characteristics of different prediction methods, this paper uses the empirical formula method, numerical simulation method and ship model test method to evaluate an icebreaker's continuous sailing in smooth ice and predict the ice resistance. MethodIn this paper, the nonlinear finite element software DYNA is used to construct ice numerical simulation models based on the traditional finite element and cohesive element methods respectively, and simulations are performed of the bending fracture and interaction process that occurs when level ice interacts with an icebreaker. At the same time, using the empirical formula method, three different empirical formulas are used to calculate the ice resistance, and a sensitivity analysis of the parameters affecting the prediction results of the empirical formula method is also carried out. ResultsThe study finds that ice resistance shows an upward trend with the increase in speed, ice thickness and bending strength. Among them, ice thickness has the greatest influence on ice resistance. Among the three empirical formulas, the prediction results of the Lindqvist formula are closer to the ship model test results, while those of the Vance and Lewis formulas are more conservative. The traditional finite element and cohesive element methods obtain more accurate ice resistance prediction results when the thickness is small. When the thickness is large, the error is about 25%. In case of small ice thickness and high speed, the ice resistance value predicted by the cohesive element method is more accurate than that of the traditional finite element method, and the accuracy error is within 10% compared with the ship model test results. ConclusionIn the actual ice resistance prediction, the empirical formula method and numerical simulation method can be combined to take into account the accuracy and efficiency of the prediction results.

The physical and mechanical properties of sea ice and the failure modes of ice sheets significantly affect the ice loading of offshore structures. This paper first introduces the physical and mechanical characteristics of sea ice, then describes the physical processes of the interaction of ice sheets with offshore structures. Finally, the progress of research on the ice loading of offshore structures is briefly analyzed, including the three main approaches of formula estimation, experimental testing and numerical simulation. By discussing the applicability of formula estimation, the research focus and difficulties of experimental testing, and the development trends of numerical simulation, we find that the model testing of ice loading is an effective method. This paper covers the research trends and problems faced by ice loading on offshore structures, and it can provide certain guiding references for the related research of scholars in the field.

ObjectivesThis paper investigates the main dimensions of ROPAX ship in the aspect of energy saving and resistance reduction.MethodsBy using ship model tests and numerical simulations, the effects of changes in the main dimension ratio of a ROPAX ship on its resistance performance are studied.ResultsThe results show that the maximum difference in effective power between different L/B schemes is only 150 W at lower speeds, increasing to 1 300 W at higher speeds, while the maximum difference in effective power between different B/T schemes is only 170 W at lower speeds, increasing to 300 W at higher speeds.ConclusionsThis paper shows that increasing the L/B value can significantly reduce the model resistance and effective power of the ship, and there is no significant difference in effective power with different B/T values.

The steam generator tube rupture (SGTR) accident is one of the design basis accidents of lead-cooled fast reactor (LFR). In the event of such an accident, a subcooled water jet is generated in the lead pool of primary circuit, which forms a complicated distribution of the liquid metal-gas two-phase flow. The detection of the two-phase interface and migration of steam bubbles is an significant part of reactor safety analysis. Due to the opacity, corrosiveness, high temperature of liquid metal, and the current limitations of measurement methods involving liquid metal-gas two-phase flow, a diamond-like carbon (DLC) coated wire-mesh sensor (WMS) based on electrical principles was proposed in this paper. The sensor could achieve the image of the liquid metal-gas two-phase distribution inside the flow channel, while preventing the corrosion failure of the sensor. Based on the COMSOL software, a numerical model of the DLC coated WMS was established. Selecting the materials of two phases as liquid GaInSn alloy and air, the simulation of the electric field in the liquid metal environment containing a single bubble was performed, and an electric signal value matrix representing the liquid metal-gas two-phase was output. The signal matrix was further normalized through the linear relation to obtain the two-phase distribution image, which verified the application feasibility of the coated WMS in liquid metal. In addition, a prototype of the DLC coated WMS was manufactured, and the numerical simulation results were experimentally validated in order to demonstrate the rationality of the numerical model. Furthermore, the influence of different structural parameters on the measurement accuracy of coated WMS was studied in detail by changing the transverse interval, axial interval, electrode diameter, coat thickness, and the size of air bubble. The simulation results show that the electric field distribution in the liquid metal-gas two-phase environment differs significantly from that in conventional fluid medias such as water-gas due to the high relative permittivity of liquid metal. On the other hand, considering the resolution of the WMS and the phenomenon of electric signal crosstalk, the transverse interval of electrode should be selected between 2-3 mm, and the axial interval should be selected between 1.5-2 mm to achieve high measurement accuracy. The coat thickness and electrode diameter have little influence on the measurement accuracy, but to reduce the intrusion effect of the WMS, the electrode diameter should be selected between 0.4-0.5 mm and the coat thickness should not exceed half of the electrode radius. This study could guide the practical application of DLC coated WMS in the liquid metal-gas two-phase environment and provide a technical basis for the analysis of multi-phase distribution under SGTR accidents.

ObjectiveThe purpose of this paper is to study the effects of cavitation models on the simulation of full-scale propeller cavitation. MethodsThe minimum rotational speed of the propeller required for cavitation is predicted by the Bernoulli equation, and the propeller's cavitation condition is observed by full-scale experiment. After determining the boundary layer mesh thickness and establishing the hydrodynamic model, meshes are generated. In the numerical simulation, the turbulence model is selected from either the standard \begin{document}$k - \varepsilon $\end{document} model or Realizable \begin{document}$k - \varepsilon $\end{document} model, and the cavitation model is selected from either the Schnerr−Sauer (S−S) model or the Zwart−Gerber−Belamri (ZGB) model. The maximum gas volume fraction on the surface of the propeller is tracked and recorded. In the meantime, the reliability of the numerical simulation is evaluated by observing the gas distribution on the surface of the propeller. And the simulation accuracy of the related models is compared. ResultsThe simulation results show that compared with the standard \begin{document}$k - \varepsilon $\end{document} turbulence model, the cavitation region obtained with the Realizable \begin{document}$k - \varepsilon $\end{document} model is significantly more consistent with the experimental results. By monitoring the maximum gas volume fraction on propeller's surface, it is found that the choice of turbulence model has little effect on the cavitation intensity, and the cavitation intensity obtained by S−S model is significantly higher than that obtained by the ZGB model. ConclusionsThis study shows that the turbulence model has a great influence on the area of the cavitation region, and cavitation models have a great influence on cavitation intensity. In terms of the simulation of propeller cavitation, the accuracy of the Realizable \begin{document}$k - \varepsilon $\end{document} model is higher than that of the standard \begin{document}$k - \varepsilon $\end{document} model.

ObjectiveThis paper aims to study the coupled dynamic response characteristics of an integrated system of a semi-submersible wind turbine and fish farming cage under wind, wave and current actions.MethodBased on the self-designed semi-submersible wind turbine SJTU-SPIC, an integrated floating wind turbine and fish farming cage concept is proposed and numerically modeled. The dynamic response characteristics of the integrated concept under wind, wave and current actions are then studied using coupled aero-hydro-servo-elastic-mooring analysis.ResultsThe numerical simulations indicate that introducing the fish farming cage can induce slightly a larger surge motion but suppress the pitch, which is beneficial for wind power production.ConclusionThe dynamic behavior of the integrated system of a semi-submersible wind turbine and fish farming cage proposed herein is similar to that of a floating wind turbine, and the system is shown to be feasible.

In order to smoothly implement gob-side entry retaining and mining without coal pillar in 3207 working face of Nanyang Coal Mine,Shanxi Province,this paper proposes to carry out advanced deep-hole blasting pre-splitting roof near gob side supporting wall.Through numerical simulation and field industrial test,the influence of deep-hole blasting roof cutting on surrounding rock stability of gob-side retaining roadway is studied.Based on the backdrop of retaining roadway along goaf in 3207 working face of Nanyang coal mine,a numerical simulation model was established,the displacement of roof and floor,wall and coal body of retained roadway,the stress distribution and variation of surrounding rock of retaining roadway were calculated.The numerical calculation shows that the variation of stress and displacement of surrounding rock in gob-side retaining roadway decreases greatly after roof cutting,and the stability of surrounding rock is improved significantly.The field industrial test results show that deep-hole blasting roof cutting can effectively eliminate the rotational extrusion damage of cantilever beam roof to surrounding rock of gob-side retaining roadway,and help to maintain the stability and integrity of gob-side retaining roadway structure.The research results of this paper can be used for reference in the design and construction of gob-side entry retaining project.

ObjectivesThis paper aims to analyze the influence of polar low temperature environment and ballast water capacity on the dynamic change process of the temperature field in polar ship's ballast tank. MethodsThe volume of fluid (VOF) model was used to simulate the two phases of gas and liquid, and the standard k-ε turbulence model was used to simulate the fluid movement. The numerical analysis model of heat transfer in the ballast tank of polar ships was established to analyze the dynamic change process of the temperature field of the ballast tank at low temperature, and reveal the influence mechanism of multiple ambient temperatures and multiple loading heights on the temperature field of the ballast tank. ResultsWith the continuous occurrence of heat transfer, the temperature in the area above the waterline of the side ballast tank decreases rapidly, and the cooling area extends laterally to the cabin and downward along the bulkhead respectively. When there is more ballast water, the temperature field in the cabin is relatively stable due to the large heat capacity of water, but the air heat capacity is low and the temperature field changes greatly, which is prone to cyclones and further affects the temperature field distribution in the calculation domain. Under the condition of the same ballast water capacity, the lower the external ambient temperature, the greater the difference between internal and external temperatures, the more intense the heat exchange, and the faster the temperature of the ballast tank changes. ConclusionsThe VOF two-phase flow model and the standard k-ε turbulence model can better reveal the temporal and spatial evolution characteristics of the temperature field in the ballast tank in polar low temperature environment, and analyze the influence of internal and external thermal boundary conditions on the change of the temperature field in the ballast tank, which can provide necessary technical reference for the cold/freeze protection of polar ships' ballast tanks.

[Objectives] The shock environment of a warship in an underwater explosion is the basic input for the design and shock resistance ability evaluation of ship equipment. [Methods] In this paper, a numerical simulation is used to analyze the shock environment in different regions of a ship, and the Second-order Doubly Asymptotic Approximation(DAA2)is used to solve the fluid-structure interaction. First, the appropriate calculating parameters are chosen, such as damping ratio, and then a series of Single-Degree-of-Freedom(SDOF) systems are attached at various deck locations to simulate flexible equipment. [Results] The accuracy and reliability of DAA2 is verified by the fact that the calculated shock spectrums at classic regions perfectly match the data of the ship shock trial. The shock response of the SDOF systems under the same shock input are then calculated and transformed into the shock environment. Finally, the results of shock environments in different regions are compared. [Conclusions] The conclusions of this paper can provide design reference data for the subsequent anti-shock design of equipment.

[Objectives] In order to investigate the strength of the joint structure of box girders under internal explosion, [Methods] this paper use the explicit dynamic finite software ANSYS/LS-DYNA to establish a large complex typical cabin model. Numerical investigations are then conducted to analyze the dynamic response of different forms of joint structure under internal explosion using the ALE algorithm. The whole deformation/failure mode of cabin structures with the same charge mass and detonation position is obtained. A comparison of stress level at typical positions is then carried out in detail. [Results] The results show that the arc-arc type joint has a lower stress level compared to the bracket at the broadside. In the central position where a box girder is connected to a web beam, the arc-arc joint form is better than the other two. [Conclusions] The findings of this paper can provide useful references for the engineering application of joint structures.

[Objectives] The shipboards of large surface ships are greatly threatened by anti-ship weapons, and a multicamerate defense structure (MDS) is usually established to ensure the safety of important internal cabins. In this paper, the dispersion effect of fragment-induced shockwaves in an MDS liquid tank is studied. [Methods]First, the elemental experiment of a miniature liquid tank struck by fragments is conducted, through which the free field pressure, etc. of typical positions in the tank are obtained. The numerical method used in this paper is then validated on the basis of the experimental results and the dispersion effects in a full-scale MDS liquid tank are analyzed. [Results] It is found that the amplitude and impulses of shockwaves in a liquid tank satisfy the exponential attenuation law as the spatial position changes. [Conclusions] The findings of this paper can provide useful references for the optimal design of MDS.

Due to the advantages of long service life, compact structure, strong environmental adaptability and high inherent safety, the heat pipe reactor power supply system is worth studying. The NUSTER2.0 dual-mode heat pipe reactor non-nuclear prototype built by Xi’an Jiaotong University adopts the integrated design of “simulated reactor core-high temperature heat pipe-Stirling generator-thermoelectric power generation”. The combination of the dynamic module coupled with Stirling and the static module coupled with thermoelectric power generation device can meet the diversified demands of energy. In this paper, the steady-state experiment of NUSTER2.0 was carried out to verify the design, and the system coupling simulation of the prototype was carried out by COMSOL multiphysics to analyze its operation and mechanical characteristics. In the 15 kW thermal power steady-state experiment, the generating power of the dynamic module is 2 019 W, and the static module is 493.2 W. The overall thermoelectric conversion efficiency is 16.7%, which verifies the engineering feasibility of the design. The system simulation model is coupled with the thermal resistance network model of high temperature heat pipe, the equivalent thermal conductivity model of thermoelectric power generation device and the Stirling adiabatic analysis program. The heat source of fuel rod and the heat sink of cooling water were simulated by heat flux boundary and convective boundary respectively. Under 15 kW thermal power, the steady-state simulation results are in good agreement with the experimental results on both the heat pipe temperature distribution and the main operating parameters of the dynamic and static modules, while the maximum relative error is 6.73%, which verifies that the coupled model is reliable. The variable thermal power steady-state simulation determines that the limit due to Stirling is 16.5 kW, and predicts that the static module will reach the peak efficiency near 25 kW. The system start-up transient simulation obtains the start-up characteristics under the 3.5-10.15 kW stepped power platform. The prototype start-up strategy based on the combination of power platform cold start and thermal insulation restart was also proposed. The thermal-mechanical coupling simulation indicates that the stress danger zone of the system is the coupling between the heat pipe and assembly matrix. Under 15 kW thermal power, the maximum stress at the coupling of heat pipe-core matrix and heat pipe-collector matrix are 160 MPa and 97 MPa, respectively. In the experiment, the self-adjusting function of the Stirling insulation ring can significantly relieve the 366 MPa stress between it and the Stirling matrix. The thermal expansion rate of the reactor core is 1.21%, which will cause negative feedback on the reactivity. The simulation results provide the numerical basis for the operation safety analysis and further experimental design of the NUSTER2.0 prototype.

To master the influence law of complex landform such as the surface mountain and the valley area between the mountains on the underlying coal rock stress, this study constructed a calculation model of the vertical stress of the coal strata under the mountain through theoretical analysis.Taking the 50205 working face of Hecaogou coal mine as example for analysis, This paper studied the complex landform on the underlying coal rock load characteristics and stress transfer law.Results show that: mountain load has significant stress effect on shallow coal seam.In the horizontal direction, the influence range is negatively correlated with the mountain slope, and the coefficient of influence range is positively related to the mountain slope.The effect of mountain on the vertical stress of the underlying coal seam can be divided into three stages: initial effect, intense growth effect and slow growth effect.The vertical stress superposition value of the underlying coal strata in the gully region firstly increases and then decreases with the change of depth.Moreover, when the distance between two adjacent mountains increases to more than.1.25 times of the width of the mountain bottom, the effect of stress superposition is very small and can be ignored.As the distance between adjacent mountains gradually increases, an inverted triangle area with insignificant stress superposition is formed in the coal strata under the gully area.

Purposes As a result of the ongoing replenishment of groundwater, a multifaceted system for the storage and circulation of groundwater has developed within overlying goaf and roadway. Coal mines encounter technical challenges in preventing and managing water damage in the roof goaf during the process of multiple coal seam composite mining, leading to a substantial requirement for daily roof water exploration and drainage engineering. Methods This paper focuses on the roof and floor rocks of coal seams as the subject of investigation. The study aims to analyze the fracture zone development between coal seams in the context of multiple seams mining, utilizing on-site electrical testing, numerical simulation, and theoretical analysis. Findings The findings of the experimental investigation indicate that the extraction of coal seams in close proximity facilitates the full interconnection of the goafs, resulting in the formation of a water accumulation zone composed of double coal seam goafs. The depth of the damage zone caused by the disturbance of the double coal seam floor is measured at 15.6 m. As the underlying working face is mined, the numbers of weak structural planes in the surrounding rock increas, leading to an expansion of the area of resistivity increase. Upon reaching a height of 58 m, the development of fracture zone gradually ceases. Optimal exploration and drainage of the roof empty water can be achieved to the fullest extent when the effective thickness of the key water barrier layer is no less than 20 m. Conclusions The concept of goaf water hazard prevention and coal mining under water-containing based on the coal seam spacing and key water-resisting layer is proposed. The conception of “finding out the structure, controlling the seam spacing, and mining after upper preventing” should be followed. The research results not only effectively prevent and control the threat of water inrush from the roof goaf, but also reduce the workload and production cost of water exploration and drainage in future. It can also provide reference for water-retaining mining technology in multiple coal seams affected by the water hazard in the roof goaf.

In the process of steelmaking, improving the flow field in ladle plays an important role in improving the purity of molten steel, homogenization of chemical composition and temperature, and shortening mixing time. Alternate stirring in ladle can improve the mixing process. In this paper, the water model of 1/5 scaled down 130 t ladle was numerically simulated by the STAR-CCM+ software. The changes of flow field, tracer transport process, and mixing time after alternate stirring at different time points were investigated. The results show that when alternating stirring is used, the flow field eventually forms a mirror image of single plug stirring, and the time required to achieve stable flow field is 55-76 s. After alternating stirring, owing to inertia, the tracer still transfers to ladle surface by counterclockwise circulation. After the formation of alternating flow field, the tracer transfers in clockwise main circulation. In this case, the dead zone is located at the front and rear parts at the bottom of ladle. The timing of alternate stirring affects the distribution ratio of tracer to participate in the counterclockwise circulation caused by inertia and the formed clockwise main circulation. Compared with single plug stirring, alternating stirring shortens the mixing time at the top monitoring points of ladle and increases the mixing time at the bottom monitoring points.

Mechanical ventilation is an important way to maintain the temperature and moisture of grain piles in the warehouse within the safe storage range, which is closely related to grain storage safety and the benefits of storage enterprises. In order to solve the disadvantages of the slow advancing speed of the inlet air in the vertical direction of the traditional Gui-shaped ventilation network, this paper proposed a new ventilation network with Gui-shaped and vertical riser to shorten the travel path and time of air or fumigation gas in the grain pile. The new ventilation network effects through numerical simulation were simulated and predicted to verify its feasibility. The results showed that the cooling rate and uniformity of this ventilation network were good, and the flow resistance of the inlet air in the vertical direction was significantly reduced. The cold front at the position of the riser could pass through the grain surface with a height of 5.5 m on the second day of ventilation, and the ventilation energy consumption could be reduced by about 16% compared with the traditional Gui-shaped ventilation network under the same conditions. The results could provide theory basis for the selection of optimal ventilation network of room type warehouse.

Spent fuel reprocessing is one of the most critical links in the process of closed nuclear fuel cycle process. Carrying out computer simulation research on this process and establishing its dynamic simulation model can carry out process analysis and optimization with less human and material resources and in a more general scope. In this paper, by analyzing the mass transfer process of the dissolution reaction between spent fuel pellets and nitric acid and the mass transfer process of solute in the solution, a dynamic dissolution model of spent fuel pellets dissolution process was obtained based on mass balance calculation. The model includes three parts: chemical reaction module, solute transfer module and solution flow field analysis module, which are respectively used to calculate the mass transfer caused by chemical reaction, the mass transfer caused by the convection and diffusion of liquid in the liquid phase and the analysis of the flow state of fluid in the solution system. The turbulent flow state of the dissolved liquid in the dissolver was simulated by Comsol software, and the flow field cloud diagram of the dissolved liquid flow was obtained, which provided the analysis data of the liquid phase flow state for the established dynamic dissolution model of the spent fuel pellet dissolution process. The numerical simulation program for solving the real-time simulation model of spent fuel pellet dissolution process was established by using Matlab software, and the feeding dynamic simulation of spent fuel dissolution process in continuous dissolver was carried out under the process conditions of 90 ℃, nitric acid feed concentration of 6 mol/L, feed flow rate of 11 L/min and return flow of 35 L/min. The change trend of the simulation results is basically consistent with the actual process, and the dissolution process needs about 2 000 minutes to reach dynamic equilibrium. After equilibrium, the concentration of nitric acid in the solution discharge is 2.78 mol/L and the concentration of uranium is 253.23 g/L. The relative error of material balance calculation of uranium in the whole dissolution process is generally in an acceptable range. When it reaches equilibrium, the relative error of overall mass balance calculation is only 2.57%. The simulation results show that the dynamic dissolution simulation model of the rotary continuous dissolver established in this study can better describe the actual dissolution behavior of the spent fuel in the dissolver, and provide simulation data support for the spent fuel dissolution process in the actual production process.

[Introduction] Scouring around pile foundation is an important technical problem in the construction and maintenance of offshore wind power plants. The scour hole developed under the environmental load like wave, current, etc. would reduce the stability of pile-soil structure and cause a non-negligible impact on the safety of the whole structure. [Method] In this paper, CFD technique combined with sand transport model were employed, scour around cylinder pile in sandy seabed under steady current was numerically simulated and studied by solving the nonlinear coupling equations of flow and scour, the development process of scour hole around pile was observed, and the time-varying curve of scour depth was obtained. [Result] The computing results show that the scour depth increases rapidly at the beginning of scouring, and then the process slows down gradually. In the calculation time of 16 minutes, the scour depth grows to 0.81 times the pile diameter. [Conclusion] According to the development of scour depth, it is suggested that for the wind farm located in sandy seabed aera, scour protection should be considered during the construction period, and the methods such as increasing the protective structures are recommended to prevent scour forming and extending.

ObjectivesIn this paper, the numerical simulation method is used to study the anti-penetration performance and energy absorption mode of a stiffened plate, as well as the influence of different stiffened bars on the flight attitude of the projectile body.Methods Finite element software LS-DYNA is used to simulate the process of a truncated oval-nosed projectile penetrating a stiffened plate, and the results of the numerical simulation are compared with an experiment to verify the reliability of the numerical simulation method. The momentum method and mass equivalence method are used to predict the residual velocity of the projectile, and the applicability of different theoretical methods within different velocity ranges is compared. The deformation energy of different regions of the stiffened plate is then extracted to analyze the influence of the initial velocity of the projectile body on the energy absorption mode of the target plate. Finally, the structure of the stiffeners is changed and the influence of the relative position of the stiffeners on the penetration attitude of the projectile body is analyzed.ResultsThe results show that the mass equivalence method is more accurate than the momentum method in predicting the residual velocity of the stiffened plate when the initial velocity of the projectile body is in the range of 300–900 m/s. The ratio of the deformation energy of the stiffened plate to the energy loss of the projectile body decreases with the increase of the initial velocity of the projectile body. The effect of a T-stiffened plate on trajectory is greater than that of a rectangular-stiffened plate.ConclusionsThe related calculation method and research results have certain reference value for research and engineering application surrounding the anti-penetration of stiffened plates.

The 2 K cryogenic system is a key subsystem of the new generation superconducting accelerator, and the 2 K heat exchanger is the key equipment. With the increasing scale of 2 K cryogenic system, the demand for high-flow 2 K heat exchanger becomes more and more urgent, and the current application of the tube and fin type, coil and tube structure of the heat exchanger is gradually replaced by a more efficient and compact platefin heat exchanger in high flow conditions, but the platefin heat exchanger has more structural parameters, and it is difficult to take into account the heat transfer efficiency, pressure drop and volume size in the design process. In this paper, based on the basic differential equations of heat transfer and pressure drop and the related flow heat transfer correlation equation, the design calculation of a 50 g/s flow rate 2 K heat exchanger supporting a 1 000 W@2 K cryogenic system was carried out using the distributed parameter method. Five parameters affecting the performance of the heat exchanger were analyzed and the comprehensive optimization index of the heat exchanger was proposed using the weighting coefficient method. Based on the proposed optimization indexes, a genetic algorithm was used to optimize the heat exchanger with multiple foci on high heat transfer efficiency, low pressure drop and small size according to the engineering needs, and a series of optimization solutions were obtained, from which the solution focusing on heat transfer efficiency was selected as the preliminary design result. Based on the parameter of this result, a threedimensional model of the heat exchanger heat transfer channel was established, and CFD numerical simulation was used for simulation calculation. The simulation results were in good agreement with the design results, verifying the accuracy of the preliminary design results, and the performance of the heat exchanger under different operating conditions was analyzed for this optimization result. The optimization result shows that the heat exchanger is selected with perforated plate type fins to cold-hot-cold (CHC) structure for the arrangement, it has 10 layers of CHC structure, its length is 760 mm, fin height is 4 mm, fin spacing is 7.9 mm, heat transfer efficiency of the heat exchanger is 84.4%, pressure drop is 222.16 Pa, and the volume is 0.022 1 m3. A variety of fin types of heat exchangers will be studied in the future to meet the demand of heat exchanger use.

To meet the design requirements of long-endurance hydrogen energy hybrid powered Unmanned Aerial Vehicle, the combined MATLAB and XFOIL optimization methods, based on the optimized airfoil, were used to optimize the design of the airfoil of HM114. Two aerodynamic layouts for straight wing and elliptical wing (HY1) were designed. Computational fluid dynamics was adopted to analyze the aerodynamic performance of the two layouts. The results show that the lift coefficient of the optimized airfoil is increased by 12.38%, and the lift-drag ratio is increased by 14.03%; the two layouts achieve the maximum lift-drag ratio when the angle of attack is α=4°, while the stall angle of attack is α=12°, the HY1 layout's smaller pressure difference can contribute more lift to UAV; the HY1 layout has better stall performance when the pressure boundary of the wing surface is behind; both schemes satisfy the longitudinal static stability, but the HY1 layout has better stability. The results of aerodynamic optimization and flow field characteristic analysis in this paper can provide a reference for the aerodynamic layout design of hydrogen energy long-endurance fixed-wing aircraft.

The aerodynamic problems caused by high-speed train passing through tunnel become more and more serious with the increase of train speed. In view of the existing line reconstruction which is limited by the terrain and can not be equipped with additional buffer structure in tunnel, we proposes a new type of inter-stepwise buffer structure. In this paper, the flow field between train and tunnel was modeled according to the k-ε two equation turbulence model, the information exchange was realized by sliding grid technology. The pressure oscillation was calculated for the initial compression wave generated when a train enters the tunnel with buffer structure at high speed. The simulation results illuminate that the inter-stepwise buffer structure has limited effect on reducing pressure peak, but it can delay pressure rise and greatly reduce pressure gradient peak. When the buffer structure is located 60 m away from tunnel inlet, the expansion form is three-way uniform expansion, the order is first, the length is 30 m, and the cross-sectional area is 150 m2, the mitigation effect of the inter-stepwise buffer structure on tunnel aerodynamic effect is the best, and the pressure gradient mitigation effect reaches 24.66%.

On the basis of CFD numerical simulation technology, the numerical simulation results of radial ventilation and cooling under different central air collection pipe forms of shallow circular silo were analyzed, and they were compared to judge the advantages and disadvantages. The grain type studied in this paper was soybean. The temperature distribution and air distribution in the grain pile under the ventilation of the top or opening or non-circulation of four variable diameter central air collection pipes were numerically simulated. The numerical simulation results of the eight cases were compared to analyze their ventilation uniformity and ventilation cooling rate. It is found that the air collecting duct has obvious advantages when its height was flush with the grain surface, thick at the top and fine at the bottom, which is mainly reflected in its ventilation uniformity. The research results provide theoretical guidance and basis for the selection of ventilation and cooling methods for soybean storage in shallow circular warehouse.

ObjectiveThe ice resistance of an ice breaker on the Yellow River is predicted in the context of ice disasters caused by the freezing of the river in winter. MethodsFirst, a ship-ice-water coupled numerical model is introduced on the basis of the smoothed particle hydrodynamics method (SPH), which includes the numerical process of the constitutive equation, yield criterion and coupling model of ice. The prediction results for the ice resistance of the icebreaker under different conditions are then given. ResultsThe results show that the prediction error of ice resistance in level ice cases is less than 17.6% compared with empirical formulas; the ice resistance of the ice breaker increases with the increase in bending strength and ice thickness, and the thickness of the ice layer is the most important factor for the ice load.ConclusionThe ship-ice-water coupled SPH method proposed in this paper can predict the ice resistance of an ice breaker in the Yellow River channel, providing references for the actual operation of ice breakers on the Yellow River.

ObjectiveIn order to improve the anti-shock perfomance of ships subjected to underwater explosion, this paper studies the energy absorption and impact resistance of the new protective structure consisted of carbon fiber reinforced plastic (CFRP)-lattice aluminum sandwich plates. MethodsFirst, finite element software ABAQUS is used to establish the numerical simulation model of CFRP-lattice aluminum sandwich plates under non-explosive and non-contact underwater explosion load, and its reliability is verified. Single variables are then controlled to analyze the influence of the fiber layer thickness of the upper and lower panels and the rod diameter of the sandwich lattice structure on the energy absorption characteristics and structural deflection of the CFRP-lattice aluminum sandwich plates. Finally, based on the above three design parameters, a surrogate optimization model is established using the experimental design method and numerical simulation methodology to optimize the energy absorption of the CFRP-lattice aluminum sandwich plate structure. ResultsThe results show that when the mass of the CFRP-lattice aluminum sandwich plates is constant, the specific absorption of the optimized results can be increased by 284%. In full consideration of the deformation of the lower plates, the specific energy absorption of the optimized results can be increased by 59%. ConclusionsThis study shows that the proposed optimized structure of CFRP-lattice aluminum sandwich plates can effectively improve their energy absorption capacity, and the response surface method is an optimization method that can effectively improve the energy absorption characteristics of the structure.

Exceeding the limit of underground hydrogen sulfide not only harms operators, but also damages underground equipment.The concentration of hydrogen sulfide in water in a coal mine roadway in Shanxi is 228.19 mg/m3, and 45.64 mg/m3in the air, rendering it a high hydrogen sulfide coal mine.The method of coal seam drilling and alkali injection is used to control hydrogen sulfide.In order to determine the optimal parameters of alkali injection, this paper uses COMSOL Multiphysics software to carry out single-hole and double-hole alkali injection numerical simulations on the process and effect of coal seam alkali injection to treat hydrogen sulfide.The simulation results of single-hole and double-hole alkali injection show that: the farther away from the drilling center, the lower the alkali injection pressure on the coal seam.The longer the alkali injection time, the larger the diffusion range of the alkali solution.And the diffusion speed of the alkali solution gradually decreases as the diffusion range becomes larger.When the distance of double-hole alkali injection is too close, the cross-flow will cause the diffusion range of the alkali solution to become smaller at the same time.The optimal simulation scheme is as follows: the hole distance is 10 m, the pressure is 8 MPa, and the alkali injection time is 48 h.After alkali injection at the 13103 working face, a 28 d on-site data monitoring was carried out.The maximum hydrogen sulfide concentration in the return air flow was 9.13 mg/m3, which did not exceed the limit during the mining, indicating that the optimal alkali injection parameters can guide the coal seam alkali injection work.

To predict the maneuverability of full-revolving propeller ships, this paper analyzes the propeller force and establishes MMG equations for controlling motion mathematical models that are suited to the full-revolving propeller model, in accordance with the modeling method of the separating ship motion model and taking into account the special nature of the force and flexibility of a full rotation in the horizontal plane of a full-revolving propeller. Secondly, hydrodynamic force derivatives for the ship model are obtained by simulating the model's PMM movement, and the controlling Ordinary Differential Equation (ODE) is solved using the four-stage Rung-Kuta method. Finally, the numerical simulation of a certain ship's rotating motion and its zigzag test in still water is obtained, and the prediction results are compared with that of a self-running model. It is found that the simulation results agree well with the trial results, and the effectiveness of the ship motion model for the full-revolving propeller model is validated. In brief, this paper provides a reliable and effective method of predicting the maneuverability of full-revolving propeller ships.

ObjectivesThis paper studies the transient effects, different frequencies of spectral peaks and meaningful excitation amplitudes on liquid sloshing. MethodsA numerical model is established using the computational fluid dynamics (CFD) method, and the reliability of the numerical model is validated through comparison with the analytical solution of linear potential flow and experimental data. ResultsThe transient effects of random excitation have a significant influence on the fluctuation of the free water surface of liquid sloshing in the tank. By applying the buffer function, stable results can be obtained quickly. When the peak frequency of the excitation spectrum is close to the natural frequency of the tank, the energy of the wave-height response spectrum of the liquid sloshing in the tank is mainly concentrated at the natural frequency of the tank. When the peak frequency of the excitation spectrum is far from the natural frequency of the tank, the energy of the wave-height response spectrum is concentrated near the peak frequency. With the increase of the meaningful amplitude of the excitation spectrum, the amplitude deviation of the liquid sloshing response relative to the linear wave (the deviation degree is zero) increases, and the nonlinearity of the tank increases significantly. ConclusionsFor the random excitation simulation, especially when the excitation frequency is far from the natural frequency, it is necessary to buffer the excitation duration. It is found that when the peak frequency of the excitation spectrum moves away from the first natural frequency to higher frequencies, the energy is dominant at the i-th order of the natural frequency when the peak frequency is close to it.

ObjectivesThis paper aims to study the kinetic and dynamic characteristics of an trans-media unmanned vehicle during vertical take-off from water.MethodsIts dynamic performance during the trans-media process from water to air is numerically simulated on the basis of the viscous computational fluid dynamics (CFD) approach combined with the overset grid technique, multiple degrees of freedom and dynamic fluid body interaction (DFBI) motion model.ResultsThe results show that in order to pull the vehicle up, the air propeller rotation speed should be higher than the speed at the same pull force provided by a single propeller. As the main movement of the vehicle is vertically upward, the coupling of the air propeller downwash flow velocity and the fuselage of the vehicle leads to the "quick bowing" phenomenon.ConclusionsTo ensure smooth take-off, a manual or automatic control program should be added to adjust the tilt angle of the thrusters in real time during the take-off process. This study provides a powerful evaluation method for the optimal design and control of trans-media unmanned vehicle in the future.

In this paper, the principle of water bag dust removal is studied by using ANSYS Fluent numerical software combined with field experiment.The influence of the detonation time difference and the distance between the water bag and the dust removal effect is analyzed emphatically.The results show that when the time difference between the first row of water bag initiation and the deep hole blasting is within the range of 1~1.5 s, the blasting water mist concentration is larger and the diffusion range is the widest, enabling the blasting water mist to fully contact with the dust cloud diffused over.When the detonation time between the first row and the second row of water bags is 0.5~1.0 s, the dust removal effect along the water bags is better.When the distance between the two water bags is 10~15 m, the coverage area of blasting atomization is larger, and the ability to capture dust after blasting is better.The field experiment results show that the dust fall at 50m increases by 27 %, the dust fall at 100 m increases by 12 %, and the dust fall at 150m decreases by 16 %.The effect of water mist and dust particles accelerates the settling of dust particles, and the dust fall in the near area increases, while the dust fall in the distance decreases.The dust concentration of the 50s after explosion is reduced by 36 % after the adoption of water mist dust capture measures.

The stress state of joints is the key to the mechanical performance of the space structure. In this paper the constant amplitude fatigue performance of the pin in space structure was investigated. The fatigue numerical simulation of 32 theoretical models with 5 factors was carried out on the basis of similar numerical models and nCode Designlife analysis software. The S-N curve was obtained and the fatigue life calculation formula was established. The analysis results indicate that: Under the symmetrical cyclic loading (R=-1), the hot spot stress of the pin locates at the contact surface of the pin with the interface of the outer and inter ear plates, and the nominal allowable stress amplitude corresponding to 2×106 cycles is 94.42 MPa. The constant amplitude fatigue performance of the pin is negatively correlated with the three parameters, the pin hole clearance, the thickness of the ear plate, and the distance between the ear plates, while positively correlated with the pin diameter and the yield strength of the pin material. The ranking of the sensitivity of the factors affecting the constant amplitude fatigue performance of the pin is: the material of pin→the clearance of pin hole→the space between ear plates→the diameter of pin→the thickness of ear plate.

[Introduction] The aim of this paper is to analyze the influence of the size and the vertical load of the pile foundation on the horizontal bearing capacity of rock-socketed piles. [Method] Based on a field test of the rock-socketed concrete pile under horizontal load, a 3-D finite difference numerical model was established and parametric analyses were performed. [Result] The results show that there is a critical rock-socketed length (ratio of length and diameter) for rock-socketed piles. Changes of the size of the pile will influence the relative stiffness of the pile and the rock, which will affect the critical rock-socketed length. With the decrease of the pile diameter, the critical socket length will increase. Within the scope of the bearing capacity of the pile and under the condition of combined vertical and horizontal load, the horizontal displacement and bending moment of the pile will have a pretty large decrease. This influence will be neglected if the vertical friction is assumed to be the same on the both sides of the pile or simplified to be at the center of the pile, which will cause error to the calculation results. [Conclusion] This study is supposed to provide contribution to the reasonable design and further research of the horizontal load of rock-socketed piles.

For the aerodynamic layout selection of a long-endurance hydrogen energy hybrid unmanned aerial vehicle(UAV), this paper carried out a numerical simulation of aerodynamic characteristics for a certain design plan, in order to provide data support for the aerodynamic layout design evaluation and modification work. In the study, the aerodynamic data at 11 angles of attack (-6°~14°) were analyzed, the results of two turbulence calculation models were compared, and the respective lift-drag characteristic curves were obtained. In addition, the flow details such as velocity field, streamline, pressure cloud graph, and pressure curve distribution, were analyzed in detail. The results show that the UAV has a high aerodynamic performance, the maximum lift-to-drag ratio 14.5 can be obtained under the attack angle of 4°, and the stall angle of attack is 8°. The aerodynamic layout design basically meets the requirements. At the same time, the distribution characteristics of speed, pressure, and flow separation are of great significance for further understanding the aerodynamic performance of the UAV. The assessment results provide a basis for the subsequent improvement of the aerodynamic layout plan.

To understand the pipeline leakage characteristics of the large-scale main gas drainage system in coal mines and the multi-physical fields of the gas flow in pipeline, a three-dimensional numerical model is developed based on Ansys CFX and the process of gas drainage pipeline leakage is investigated.The influence of different leakage positions, different leakage intensities, and different negative pressures of the pumping station on the gas flow in the gas drainage pipeline is studied.The results show that the leakage intensity and the negative pressure are the important factors affecting the internal gas flow field in the gas drainage pipeline, and the leakage occurring near the pumping station of main gas drainage system is prone to be captured easily.The results of this paper are expected to provide technical support for the safety prevention and control of pipeline leakage accidents in the main gas drainage system and also suggestions for the optimization of the allocation of safety prevention and control resources.

ObjectivesThis paper studies the hydrodynamic performance of the submarine sailing near the ice surface using numerical simulation method.Methodsthe Suboff full-appended model, RANS method, SST k-ω turbulence model and volume of field method are used to calculate the hydrodynamic performance of the submarine in the STAR-CCM+ software. The effectiveness of the calculation method is guaranteed by the method of grid independence verification and the method of hydrodynamics analysis near the ice surface.ResultsThe results show that when the submarine sails under ice surface, the total resistance coefficient of submarine decreases with the increase of the submergence depth at the same Froude number, and decreases with the increase of Froude number at the same depth. In addition, when the dimensionless depth is greater than 1.63, the submergence hardly affects the drag coefficient.ConclusionsStudies have shown that the total drag coefficient of submarine is greatly influenced by Froude number and submergence depth. With the increase of submergence depth, the influence of submergence depth on drag coefficient decreases gradually.

[Introduction] Now the coal-fired units have more advantage of bidding to access the net, It also puts forward higher requirements for fine design and optimization of flue gas, air and pulverized coal pipeline in order to achieve the purpose of saving energy and reducing consumption. [Method] The article mainly used the combined research method of theory analysis and practice verification, firstly the function of different flue gas, air and pulverized coal pipeline system are analyzed and discuss theoretically in the view of saving energy and reducing consumption, according to the results of theoretical analysis the article proposed optimization design of the detailed rules for the implementation of different system, the numerical simulation software was used to verify the theoretical results preliminarily, At the same time, the application and practice of the actual project were verified. [Result] The research method of the energy-saving and consumption-reduction scheme proposed for the flue gas, air and pulverized coal pipeline system has been proved theoretically and by practices that it has remarkable energy-saving effect, which can not only reduce the initial investment of the system, but also reduce the annual operation expenditure of the unit. [Conclusion] Although the relevant research results in this paper are based on 1 000 MW units, the basic theories and research methods are commonly applicable to other graded unit projects, which can provide important reference for the design of energy conservation and consumption reduction of flue gas, air and pulverized coal pipeline in subsequent projects.

[Objectives] Underwater hydrofoils have the characteristics of drag reduction and energy conservation. They are often used in the design of rudder and fin stabilizers for high-performance ships. From current research on the hydrodynamic performance of hydrofoils,such improvements as opening the inner groove and adding a leading edge nodule can significantly improve their hydrodynamic performance.[Methods] In this paper,an NACA0012 hydrofoil with internal slots is improved,the influence of different internal slots on the hydrodynamic performance of the hydrofoil is studied by means of computational fluid mechanics,and the relevant action mechanism is explored.[Results] Finally,it is concluded that the hydrodynamic performance of the hydrofoil can be improved most significantly by placing the elliptical inner groove at the leading edge of the hydrofoil,and the inner groove should have a certain width to ensure a smooth flow.[Conclusions] The results of this study can play a certain role in the improvement of ship rudders.

[Objectives] When research is conducted for the centrifugal pumps' structural design and performance,the influence of the seal ring clearance is often neglected. However,the clearance of the seal ring will not only change the external characteristics of the centrifugal pump,but also affect its flow field distribution.[Methods] In this paper,a vertical centrifugal pump with medium-specific speed is used as the research object. The ANSYS CFX is used to simulate and analyze the influence of different wear-ring clearances(0,0.5,0.7,1.06 mm)on the external characteristics,pressure distribution,and velocity distribution of the centrifugal pump.[Results] The results show that the external characteristics of the centrifugal pump with different annulus clearances are consistent with the experimental data. The relative error of two is less than 5%(except 1.06 mm clearance). This verifies the reliability of the numerical simulation. With the increase of the clearance of the seal ring,the head of the centrifugal pump decreases by 20% and the efficiency by 15% under design conditions. The local pressure of the front and back cover plates of the impeller at the small clearance increases,and the overall pressure at the large clearance decreases,resulting in the radial pressure distribution of the impeller cover plate being asymmetric. The gap of the annulus leads to turbulence in the fluid and the pressure and velocity at the inlet and outlet of the centrifugal pump present an uneven gradient distribution.[Conclusions] The research results can provide a reference for the structural design and flow field analysis of the centrifugal pump.

[Objectives] To meet the functional requirements of a special purpose ship,large bulbous bow should be installed at the fore-body as the carrier of special equipment. In order to overcome the adverse effect of large bulbous bow as a special appendage on ship rapidity,the optimal design of high-speed hull form fusion special type bulbous bow was carried out.[Methods] By using the method of gradual approach to analysis,The hull and its appendages were compared and analyzed,the ship with high resistance performance was selected by numerical simulation,which was verified by model test.[Results] The results show that the hull form of round bilge fused cylindrical bulbous ship is a hull form that can meet the layout requirement and has high performance.[Conclusions] Under the same calculation conditions,the numerical simulation can accurately predict the resistance differences among different hull forms,the multi-plan optimization design approach proposed in this paper is an effective method to optimize hull forms.

In this paper, Brazilian disc splitting tests on coal rock specimens with bedding planes and corresponding simulations by combined finite/discrete numerical method(FDEM) were carried out.The results show that the angle of bedding plane have a significant influence on fracture pattern and tensile strength of coal.It is clear that as the angle of weak plane increases, the fracture pattern of models can be classified into four types, including stretching failure perpendicular to weak bedding planes, complicated sketching and shear mixed pattern, shear failure along the bedding planes, and sketching damage along weak bedding planes.As for the difference of tensile strength values, it is observed that when the load is perpendicular to the bedding plane, the effect of bedding structure on calculating tensile strength is negligible and the tensile strength value decreases with the angle rising up to the minimum value as angle reaches vertical.In addition, with respect to dissipated energy of coal samples, it is concluded that the dissipated energy gradually decreases when the angle of bedding planes are increased, which have a relationship with varied fracture patterns and strength values.

Objectives This study is focused on whether CFD can be used to analyze the temperature distribution in the core storage of ocean exploration vessels.Methods In the core storage of ocean exploration vessels, high-temperature storage is 4℃, low-temperature storage is -20℃ and temperature control accuracy is ±1℃. The standard k-ε turbulence model is used in this paper for CFD simulation. In the case of an empty storage ceiling, a transverse layout, a longitudinal layout and an oblique layout are separately adopted on the deployment scheme of the air cooler for high and low temperature storage. The temperature distributions of the different layout schemes are simulated to determine the optimal layout of the air cooler. Then the simulation results are compared with the experimental results.Results The result shows that when the air cooler adopts the transverse ceiling layout, the temperature deviation degree is small, and the temperature is mostly distributed in qualified areas, therefore this layout is selected. In the case of the transverse layout ceiling arrangement, the error between the simulation results and experiment results, is below 10%. This shows that the simulation results are reasonable.Conclusions CFD can accurately simulate temperature distribution in core storage, providing a strong scientific basis for the future design of core storage air coolers.