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This study presents an innovative scraper pump design. The design utilizes the synchronized movement of the upper and lower scrapers of the rotor to adjust the cavity volumes on either side, facilitating efficient fluid transfer. Unlike previous studies, scraper pumps face the challenge of dynamic contact between the scraper and the rotor due to their unique structure. A viscous wall strategy was employed to address hydrodynamic challenges at the point of contact, significantly improving performance prediction accuracy. The experimental data verified the accuracy of the simulation model, and the mass flow rate deviation between the simulation results and the experimental results was maintained within 10% when the viscosity at the contact point was set to 40 times the original medium viscosity. In addition, the study examined the effect of different operating speeds and load pressures on the pump performance. The results indicated that the outlet flow rate decreased by 22% when the pressure was increased from 2 MPa to 10 MPa and increased by 88.24% when the speed was increased from 900 r/min to 2200 r/min. These quantitative analyses provided valuable insights into optimizing scraper pump design and offered clear guidance for improving hydraulic performance and operational efficiency. [ABSTRACT FROM AUTHOR]

A numerical investigation of the particle deposition characteristics inside film holes and on the blade was conducted using an improved particle deposition model and dynamic grid updating. The computation model was numerically simulated using Reynolds-Averaged Navier-Stokes (RANS) equations with second-order spatial accuracy and the SST k-ω turbulence model, combined User Defined Function (UDF) in FLUENT 2021R1. The influence of the deposition morphology on film effectiveness was analyzed. The results revealed that a conical deposition in the exit region inside the film holes enhanced the separation of the coolant ejected from the film holes at a low coolant mass flux ratio (MFR). Increasing the MFR inhibited deposition, and the enhanced particle detachment significantly reduced particle deposition inside the film holes. Deposition downstream of the film holes significantly affected the cooling performance. Strip deposition on both sides of the region covered by the coolant limited the spanwise diffusion of the coolant. Compared to the non-deposition case, The surface-averaged film effectiveness was lower after deposition at MFRs of 0.1%-0.5% and slightly higher at MFRs of 0.6%. The most significant reduction in the surface-averaged film effectiveness after deposition was 34.9% at an MFR of 0.3%. [ABSTRACT FROM AUTHOR]

With the expansion of tunnel construction scale, accurate modeling of 3D unsteady flow fields in ultra-long tunnels requires high computational resources. In this study, a resistance compensation method based on the St and Eu similarity criterion is proposed to construct the simplified model to rapidly and precisely replicate the train-driven unstable airflow. A 6000 m ultra-long tunnel is utilized as a reference model and simplified models with the scale ratio varying from 80% to 10% are developed to assess the method performance. The multi-region dynamic mesh model is employed to simulate train tracking motion. After weighing the computational accuracy and efficiency, the results show that 20% is the optimal scale ratio. The unsteady wind speed of the simplified model deviates 6.96% from the reference model, while the simulation computation time is reduced by 85.01%. On this basis, the simplified model is applied to analyze the impacts of tunnel friction coefficients, blockage rates, train lengths and speeds, and departure intervals. The mean bias error (MBE) and Pearson correlation coefficient (PCC) are within 10% and over 0.8 respectively, confirming the reliability of the simplified model. The resistance compensation method is a crucial technique to improve the accuracy and efficiency of the unsteady flow field in ultra-long tunnels. [ABSTRACT FROM AUTHOR]

This paper investigates the hydrodynamic characteristics of a rectangular otter board in different working postures by using a dynamic model. Dynamic models are mainly based on dynamic mesh techniques. The results of the dynamic model are, compared to the model test, carried out in a flume tank. Furthermore, different rotation speeds of dynamic model were analyzed. The research results are as follows: compared to flume tank results, the maximum error of the dynamic model is 23.77%. Moreover, the influence of rotation speed on the hydrodynamic board is not obvious, and 2 deg./s was chosen as the rotation speed. When the board is tilted slightly (including four working postures), its lift-to-drag ratio first increases slightly and then gradually decreases. Compared with the other three working postures, the pressure center coefficient of the board does not change significantly when it is tilted inward. When studying different working angles (including AOA and tilt angle) of the otter board, the numerical dynamic model significantly reduces repetitive setup work, making simulations more efficient. Its ability to provide continuous curves and a large volume of results offers researchers a more detailed and comprehensive understanding of the board's hydrodynamics. Additionally, the dynamic model supports innovative fishery equipment development by allowing more accurate and continuous numerical simulations. [ABSTRACT FROM AUTHOR]

Background: The Lichtenstein open anterior approach with static flat meshes, the most popular inguinal hernia repair technique, has raised concerns regarding mesh fixation, defect patency, and poor quality biological response. To address these issues, the 3D dynamic ProFlor scaffold promoting a fixation-free hernia defect obliteration has been developed as an alternative. Methods: The results of open inguinal hernia repair with the ProFlor approach compared with those of the Lichtenstein repair were evaluated. Results: In a time frame of 24 months, two cohorts of patients were enrolled, 95 in the ProFlor group and 93 in the Lichtenstein group. ProFlor demonstrated superior outcomes compared to the Lichtenstein technique, with shorter procedure times, decreased intraoperative complications, and lower rates of postoperative complications. Additionally, ProFlor provided enhanced postoperative pain relief, a faster return to daily activities, and no long-term discomfort. No chronic pain was reported in the ProFlor group and 11.8% reported chronic pain in the Lichtenstein group. Conclusions: The results highlight the need to reevaluate the conventional Lichtenstein approach and align it with recent scientific progress. Further consideration of the evolving understanding of inguinal pathophysiology and groin protrusion genesis is crucial for advancing surgical techniques. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract This study presents an innovative scraper pump design. The design utilizes the synchronized movement of the upper and lower scrapers of the rotor to adjust the cavity volumes on either side, facilitating efficient fluid transfer. Unlike previous studies, scraper pumps face the challenge of dynamic contact between the scraper and the rotor due to their unique structure. A viscous wall strategy was employed to address hydrodynamic challenges at the point of contact, significantly improving performance prediction accuracy. The experimental data verified the accuracy of the simulation model, and the mass flow rate deviation between the simulation results and the experimental results was maintained within 10% when the viscosity at the contact point was set to 40 times the original medium viscosity. In addition, the study examined the effect of different operating speeds and load pressures on the pump performance. The results indicated that the outlet flow rate decreased by 22% when the pressure was increased from 2 MPa to 10 MPa and increased by 88.24% when the speed was increased from 900 r/min to 2200 r/min. These quantitative analyses provided valuable insights into optimizing scraper pump design and offered clear guidance for improving hydraulic performance and operational efficiency.

A numerical investigation of the particle deposition characteristics inside film holes and on the blade was conducted using an improved particle deposition model and dynamic grid updating. The computation model was numerically simulated using Reynolds-Averaged Navier-Stokes (RANS) equations with second-order spatial accuracy and the SST k-ω turbulence model, combined User Defined Function (UDF) in FLUENT 2021R1. The influence of the deposition morphology on film effectiveness was analyzed. The results revealed that a conical deposition in the exit region inside the film holes enhanced the separation of the coolant ejected from the film holes at a low coolant mass flux ratio (MFR). Increasing the MFR inhibited deposition, and the enhanced particle detachment significantly reduced particle deposition inside the film holes. Deposition downstream of the film holes significantly affected the cooling performance. Strip deposition on both sides of the region covered by the coolant limited the spanwise diffusion of the coolant. Compared to the non-deposition case, The surface-averaged film effectiveness was lower after deposition at MFRs of 0.1%-0.5% and slightly higher at MFRs of 0.6%. The most significant reduction in the surface-averaged film effectiveness after deposition was 34.9% at an MFR of 0.3%.

Fertigation technology plays a crucial role in the fertilizer utilization efficiency and sustainable development of modern agriculture. Among them, the piston-type fertilizer injection pump serves as the vital equipment for the uniform fertilizer injection in the large-scale irrigation systems. In this study, the numerical investigation and experimental validation were presented on the internal flow and external performance of the piston-type fertilizer injection pump during reciprocating motion. A three-dimensional numerical simulation model for the transient flow in the piston fertilizer injection pump was established based on the dynamic mesh and the RNG k-ε turbulence model. The gap between the dynamic mesh boundary and the static boundary was treated by thegap model with zero mass flux into the gap grid. The motion of the valve core in the flow field was analyzed by the six degrees of freedom (6DOF) solver. The external properties of the piston injection pump under different conditions were investigated, and the internal flow field characteristics of the pump under nominal condition were analyzed. The reliability of the numerical simulation model was verified by comparing the predicted flow rate with the experimental and theoretical data. It was found that the maximum relative error between the predicted and the experimental time-averaged flow rates was 3.58% for different strokes. The instantaneous flow rates were obtained from the numerical simulations and theoretical calculations. A high degree of consistency was demonstrated in both magnitude and trend, with the maximum relative error of 3.17%. The high velocity zone was concentrated in the flow channel of the outlet check valve, with the maximum velocity of 7.74 m/s, during the discharge phase of the pump. While a significantly increased pressure observed in the pump chamber with the maximum relative static pressure of 69.1 kPa. In the suction stage of the pump, the high flow velocity area was mainly concentrated in the inlet check valve channel. The maximum flow velocity of 8.05 m/s was found to increase the vacuum degree within the pump, resulting in the minimum relative static pressure of -79.8 kPa. In contrast to the discharge stage, the liquid in the suction process entered the pump cavity through the inlet valve, and then impinged on the wall of the pump chamber, indicating the complex mixing and turbulent structure within the pump cavity. There was a lag behavior at the initial stages of both the discharge and suction during the reciprocating motion of the piston. The formation of backflow was attributed to the delayed closure of the inlet and outlet valve core. A sudden change in the instantaneous flow rate of the fertilizer injection pump was also observed. The time of the sudden change was consistent with the time of valve core closure. The amplitude of the flow rate variations in the inlet and outlet valves at the sudden change point were equivalent. The timeaveraged flow rate of the fertigation piston pump showed a positive linear correlation with the ratio of piston stroke (k) and reciprocating frequency (f). The volume coefficient of the fertilizer injection pump decreased with the decrease of the piston stroke, but there was no significant change with the reciprocating frequency of the piston. Meanwhile, the measured volume coefficient of the variable frequency regulation differed by only 2.65% from the rated operating condition at the low flow rate (k=20% and f=10 Hz). In contrast, the volume coefficient of the variable stroke regulation differed by as much as 13.94%. Therefore, the frequency modulation control can be expected to more accurately regulate the flow rate of the piston injection pump. It is an optimal strategy for regulating the fertilizer injection in fertigation systems. The findings can provide a strong reference to optimize the fertigation piston injection pump. [ABSTRACT FROM AUTHOR]

This study investigated the flow characteristics of the high-flow path of a two-dimensional supersonic intake in a turbine-based combined-cycle engine utilizing Reynolds-averaged Navier–Stokes (RANS) and detached eddy simulation (DES) turbulence schemes with a moving mesh in ANSYS to analyze the flow effects of varying rotational cowl angles. In addition, proper orthogonal decomposition (POD) was employed to analyze the flow modes. This study revealed that the mass flow rate and pressure recovery increased linearly with an increasing cowl opening angle, and fluctuations were observed when the cowl was positioned parallel to the ramp surface in DES transient solutions. Conversely, a significant decrease in mass flow rate and pressure recovery ratio occurred when the cowl angle was located at fixed − 4.78° in steady solutions. POD utilizing snapshots derived from RANS k-wSST and DES indicated that the first to fourth modes were dominant, accurately representing the original velocity field with a cumulative mode energy ratio of over 80 %. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

【Background and Objective】 Pressure regulators (PR) are an indispensable component in irrigation systems, particularly in large-scale hilly terrain, ensuring precise water distribution and system efficiency. The performance of PRs heavily relies on the parameters of their internal springs, yet their design requires refinement. This paper aims to propose an efficient and accurate method for rapid design of the pressure regulator springs. 【Method】 The method was based on CFD by using an adaptive mesh technology to construct a model for solving for the spring parameters. We developed a model to determine the spring parameters, by using the PR with a cup-shaped moving part as the case study. We established a comprehensive spring parameter design process and devised a rapid design method based on the force balance principles and Hooke's law. In the numerical model, the outlet pressure was meticulously set to meet specific preset pressure specifications, ensuring design precision. Various inlet boundaries were designed to control the regulating range and ensure stable pressure regulation. Additionally, convergence conditions were established to guarantee that applicable flow rates met design requirements. By configuring appropriate boundary and convergence conditions, our method facilitates efficient spring parameter configuration and achieves multi-objective optimization. 【Result】 ①The absolute error of the design outcomes was less than 2%. ② For a fixed-structure PR, the preload of the configured spring exhibited a positive correlation with the design preset pressure value. However, the relationship between spring stiffness and precompression length with the preset design pressure value was more complicated. When the design PR preset pressure was determined, the preload force of the spring was inversely linearly correlated to the pressure-adjusting cross-sectional height and the water pressure area upstream of the moving part, and was linearly correlated to the water pressure area downstream of the moving part. The interaction effect of PR structural parameters on spring preload force was not significant, but there was a notable interaction effect on spring stiffness and compression length. 【Conclusion】 The proposed method can circumvent the issues associated with the traditional pressure regulator design and can thus be used as an improved method for PR spring design.

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

AbstractIn this paper, the fluid-solid interaction of a jet pump of a boiling water reactor type 5 (BWR/5), with its riser subjected to a leakage flow through its slip joint, is reported. This is a fluid-elastic instability problem. A methodology is proposed for the evaluation of the velocity of the fluid at the slip joint with and without a labyrinth seal. It is calculated with computational fluid dynamics. The results show that such a seal reduces the velocity of the fluid and produces a stable and linear behavior between the inlet and the outlet fluid velocities at the slip joint. Then the first five natural frequencies of the jet pump assembly are evaluated. The range is between 24.74 Hz and 60.21 Hz. The mass of water inside and outside of such an assembly is considered. With these data and the dimensions of the slip joint, a finite element mesh is developed and the time step (∆t = 0.001 s) is determined. The fluid and structure mesh are coupled. The fluid flow through the slip joint without a labyrinth seal is evaluated with a two-way fluid-structure interaction under normal conditions of operation. Accelerations up to 8 g can be developed at the bottom of the mixer.The fluid flow is estimated during the first 0.25 s. Flow-induced vibration can be exacerbated in resonance conditions. These values are similar to those obtained in the experimental analyses reported in the open literature. One of the excitation frequencies caused by the interaction between the fluid and the structure was close to the third natural frequency of this assembly (46.99 Hz). If the integrity of the labyrinth seal is maintained, the jet pump will not present high-amplitude oscillations. Therefore, an adequate management of seal degradation is required and failures of the jet pump can be avoided. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the flow and pressure pulsation characteristics of hydrogen circulation pump under varying pressure differences. A dynamic mesh technology was employed to conduct an unsteady numerical simulation of the interior of the hydrogen pump. The pressure pulsation within the pump cavity area was analyzed using fast Fourier transform, and the unevenness of pressure and flow inside the pump under varying pressure differential conditions was specifically studied. The results reveal that interference between dynamic and static in the pump cavity, caused by meshing clearance between rotors and radial clearance between the rotor and pump cavity, leads to pressure pulsation peaks occurring at twice the rotational frequency at all monitoring points. Additionally, as the pressure difference increases, the exhaust flow rate at the outlet of the pump cavity decreases from 49.237 m3/h to 12.392 m3/h, while volumetric efficiency decreases from 85.95% to 32.3%. The article utilizes Fluent dynamic mesh technology to conduct transient simulations on four distinct pressure differential conditions of hydrogen circulation pumps, thereby obtaining the variation principle of the internal flow field under varying pressure differences and elucidating the influence of pressure differences on both the non-uniformity of pressure and flow rate. [Display omitted] • Analyzed the reasons for two pressure pulsations occurring in the pump chamber. • Studied the pressure field to perform a total of 4 suction and exhaust in one cycle. • The pressure unevenness coefficient descents with the rise of pressure difference. [ABSTRACT FROM AUTHOR]

A hydrokinetic turbine with a vertical axis is specifically designed to harvest the kinetic energy from moving water. In this study, three vertical axis water turbines, namely Gorlov, Darrieus, and Savonius turbines, were compared for their efficiency via numerical modeling for steady-state conditions via the ANSYS 2022 R2 Fluent model. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) was implemented with an SST k-ω turbulence model. The dynamic mesh technique, which allows modeling according to changes in angular velocity at each time step, was used to simulate flow around the turbines for six different velocities (from 0.5 to 3 m/s). The efficiency of the turbines was compared and the results were analyzed. The pressure, velocity, and turbulence kinetic energy distributions around the rotor were measured at different rotational angles and results indicated a wider operating range for the Darrieus and Gorlov turbines compared to the Savonius turbine. The highest power coefficient of 0.293 was achieved in the model featuring a Darrieus turbine, corresponding to a TSR value of 1.34, compared to 0.208 for the Gorlov and 0.257 for the Savonius turbine, at TSR values of 1.3 and 1.06, respectively. Numerical modeling results pointed to a significantly higher self-starting capacity for the Savonius turbine compared to the others. [ABSTRACT FROM AUTHOR]

Peristalsis is a common motion in various biological systems, especially the upper urinary tract, where it plays a pivotal role in conveying urine from the kidneys to the bladder. Using computational fluid dynamics, this study aims to investigate the effect of various peristaltic parameters on the motion of an obstacle through a two‐dimensional ureter. Methodologically, Incompressible Navier–Stokes equations were utilized as the fluid domain's governing equations, and the Dynamic Mesh method (DM) was employed to simulate the peristaltic and obstacle motion. The peristaltic motion was modeled by a sinusoidal contraction wave propagating alongside the ureter at the physiological speed, and the motion of the obstruction through the ureter, which is caused by the fluid forces applied on its surface, was explored using the equation of Newton's second law. Various test cases of different shapes and sizes were supposed as kidney stones to understand the influence of the peristalsis properties on the stone removal process. The results show that the motion of the kidney stone is highly influenced by the gradient pressure force applied to its surface in the fluid domain. Moreover, investigating the effects of the peristaltic physical properties on the obstacle's motion indicates that the stone's motion is dependent on these parameters. Furthermore, this analysis provides insight into the peristaltic motion effects, assisting physicians in developing new medicines to facilitate the kidney stone removal process based on its shape and size. [ABSTRACT FROM AUTHOR]

Abstract A continuous increase in levels of atmospheric pollution and emission restrictions has forced scientists and engineers to adopt new strategies to improve and develop internal combustion engines. One strategy is based on the development of new simulation methodologies using computational fluid dynamic (CFD) techniques, proposed in the present article. In this study,the dynamic loop methodology with ANSYS Fluent code is proposed to perform the numerical simulation ofa four-stroke spark ignition engine. The complexity of the real case was first simplified with three-dimensional CAD geometry, which was then discretized in ANSYS Meshing, whereby a hybrid mesh was created using prismatic and tetrahedral elements. Simulations for in-cylinder analyses were performed in cold flow and employing common flow parameters, such as swirl and tumble. The mesh quality results were classified as good or excellent, being higher than 0.79 for orthogonal quality criteria and lower than 0.36 for skewness criteria. Turbulent effects were introduced concerning the opening and closing of the valves. It was found that the turbulence increases during the intake stroke up to 90°, and during the power stroke, wherein the of the piston bowl, had a great contributionthat can be seen from the swirl and tumble profile for the engine cycle. In the case of the turbulence intensity, a sharp increase was registered during the admission step up to 90°, at which point the turbulence intensity was 4.0. It canbe concluded that this is an innovative approach, capable of simulating the engine motion profile in cold flow.

Introduction: Flow dynamics due to the peristaltic pumping has been the topic of great interest for the researchers. But numerical and analytical analyses for the peristaltic motion are limited where flow domain is deformed real-time. Research on peristalsis has a limitation where theoretical aspects of walls motion are considered, neglecting the real time deformation of the walls.Objectives: This paper aims to propose a more reliable and accurate numerical methodology for peristaltic motions to address the above-mentioned challenge. Stream traces, velocities, and pressure drops along the tube is to be visualized more accurately.Methods: In present study a finite volume based dynamic mesh motion method is adopted to analyze the peristaltic motion of a non-Newtonian Quemada fluid in an axisymmetric channel. The walls and interior domain of the channel is dynamically deformed for a sinusoidal wave traveling on boundary.Results: Simulation of unsteady flow behavior for time t=0s to 2s and amplitude ratio Φ=0.2,0.4,and0.6. predicts fluid trapping phenomenon. Rotation of fluid particles is more prominent for higher amplitude ratios. Pressure gradient increases with increasing amplitude ratios.Conclusion: A novel dynamic mesh method is proposed for peristaltic pumping. It provides more accurate and more physical results for stream traces; pressure drops and velocities along the tube. A limited case of the study validates the theoretical and analytical results already presented in literature; hence the method is reliable.

This paper investigates the hydrodynamic characteristics of a rectangular otter board in different working postures by using a dynamic model. Dynamic models are mainly based on dynamic mesh techniques. The results of the dynamic model are, compared to the model test, carried out in a flume tank. Furthermore, different rotation speeds of dynamic model were analyzed. The research results are as follows: compared to flume tank results, the maximum error of the dynamic model is 23.77%. Moreover, the influence of rotation speed on the hydrodynamic board is not obvious, and 2 deg./s was chosen as the rotation speed. When the board is tilted slightly (including four working postures), its lift-to-drag ratio first increases slightly and then gradually decreases. Compared with the other three working postures, the pressure center coefficient of the board does not change significantly when it is tilted inward. When studying different working angles (including AOA and tilt angle) of the otter board, the numerical dynamic model significantly reduces repetitive setup work, making simulations more efficient. Its ability to provide continuous curves and a large volume of results offers researchers a more detailed and comprehensive understanding of the board’s hydrodynamics. Additionally, the dynamic model supports innovative fishery equipment development by allowing more accurate and continuous numerical simulations.

AbstractThe effect of horizontal wave baffles on slosh reduction of rectangular tanks under combined surge and pitch excitation is investigated in this work. Two-dimensional numerical modeling of a rectangular tank is performed using the Volume of Fluid (VoF) technique. The validation studies are performed, and the results agree with the data available in the literature. This study also considers the influence of baffle characteristics on sloshing reduction, such as wave baffle amplitude and the number of wave baffle cycles. The cosine baffles with negative amplitude and increased baffle amplitude performed better than others. [ABSTRACT FROM AUTHOR]

Ionic compressors are promising applied in hydrogen refueling stations. Ionic liquid covers a solid piston for sealing and cooling. It is necessary to investigate flow and heat transfer processes inside the cylinder. This study performs a two-phase CFD simulation incorporating valve motion by dynamic mesh method. Results show that the flow through the valves enhances heat transfer over the liquid surface. It is hard to transform the compression stage into an isothermal process, which is attributed to the low velocity of hydrogen flow. The liquid surface produces relatively severe deformation when the piston moves downward, since the flow through the suction valve impinges on the liquid surface. Furthermore, a novel conjugate heat transfer (CHT) model is proposed for calculating heat transfer between hydrogen and ionic liquid, which has a good agreement with the CFD results. Ionic liquid can decrease the hydrogen temperature at the initial stage of a multi-cycle process. The cooling effect of the ionic liquid abates as its temperature increases. This study can provide a technical reference for fast calculation of gas-liquid heat transfer of ionic compressors. [Display omitted] • Flow through valves enhances gas-liquid heat transfer. • Impingement of intake hydrogen causes liquid surface deformation. • A novel heat transfer model is proposed and validated by CFD results. • Cooling effect of ionic liquid abates as its temperature increases. [ABSTRACT FROM AUTHOR]

In this investigation, the utilization of water waves as the fluid medium is explored in the context of turbines, which are mechanical devices that convert fluid motion into rotational motion. The Volume of Fluid (VOF) model in Ansys Fluent is employed to generate regular waves and analyze the turbine's movement in a wave tank. Essential parameters such as force, pressure, momentum, and speed of the turbine are investigated to harvest electrical energy from wave energy. The study aimed to understand how these parameters changed with varying wave characteristics. Results showed that dynamic pressure and moment increase as the wavelength increased. However, the turbine's rotation speed decrease as wavelength increased. The force acting on the blades do not change significantly with wavelength but caused a time delay. The highest force applied to the turbine blades is observed at a wave height of 2 m, reaching 8000 N. Finally, the maximum turbine speed is attained at a wave height of 2 m and wave period of 7 s, reaching 87 mm/s. However, the maximum efficiency of 19.18% is achieved at a wave height of 1m and a wave period of 8.75 seconds. Because as the wave height increases, the power of the wave increases significantly, but the absorption of this power increases at a lower rate. Therefore, this study highlights the need to increase the number of wave energy conversion systems that can operate efficiently for wave forms with high wave heights. [ABSTRACT FROM AUTHOR]

A continuous increase in levels of atmospheric pollution and emission restrictions has forced scientists and engineers to adopt new strategies to improve and develop internal combustion engines. One strategy is based on the development of new simulation methodologies using computational fluid dynamic (CFD) techniques, proposed in the present article. In this study, the dynamic loop methodology with ANSYS Fluent code is proposed to perform the numerical simulation of a four-stroke spark ignition engine. The complexity of the real case was first simplified with three-dimensional CAD geometry, which was then discretized in ANSYS Meshing, whereby a hybrid mesh was created using prismatic and tetrahedral elements. Simulations for in-cylinder analyses were performed in cold flow and employing common flow parameters, such as swirl and tumble. The mesh quality results were classified as good or excellent, being higher than 0.79 for orthogonal quality criteria and lower than 0.36 for skewness criteria. Turbulent effects were introduced concerning the opening and closing of the valves. It was found that the turbulence increases during the intake stroke up to 90°, and during the power stroke, wherein the of the piston bowl, had a great contribution that can be seen from the swirl and tumble profile for the engine cycle. In the case of the turbulence intensity, a sharp increase was registered during the admission step up to 90°, at which point the turbulence intensity was 4.0. It can be concluded that this is an innovative approach, capable of simulating the engine motion profile in cold flow. [ABSTRACT FROM AUTHOR]

Copyright of Water Conservancy Science & Techonlogy & Economy is the property of Water Conservancy Science & Technology & Economy Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Large Electric Machine & Hydraulic Turbine is the property of Large Electric Machine & Hydraulic Turbine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Velocities and Shear stress on axial axis. [Display omitted] • This article proposes a novel dynamic meshing technique for peristaltic pumping problems. This numerical technique is based upon finite volume method. • It provides more accurate results when unsteady solutions in fixed coordinates are to be discussed. • Proposed method is applicable to Newtonian as well as non-Newtonian fluid models. • As an application a peristaltic flow of non-Newtonian Quemada fluid is investigated in axisymmetric channel. Introduction: Flow dynamics due to the peristaltic pumping has been the topic of great interest for the researchers. But numerical and analytical analyses for the peristaltic motion are limited where flow domain is deformed real-time. Research on peristalsis has a limitation where theoretical aspects of walls motion are considered, neglecting the real time deformation of the walls. Objectives: This paper aims to propose a more reliable and accurate numerical methodology for peristaltic motions to address the above-mentioned challenge. Stream traces, velocities, and pressure drops along the tube is to be visualized more accurately. Methods: In present study a finite volume based dynamic mesh motion method is adopted to analyze the peristaltic motion of a non-Newtonian Quemada fluid in an axisymmetric channel. The walls and interior domain of the channel is dynamically deformed for a sinusoidal wave traveling on boundary. Results: Simulation of unsteady flow behavior for time t = 0 s to 2 s and amplitude ratio Φ = 0.2 , 0.4 , a n d 0.6. predicts fluid trapping phenomenon. Rotation of fluid particles is more prominent for higher amplitude ratios. Pressure gradient increases with increasing amplitude ratios. Conclusion: A novel dynamic mesh method is proposed for peristaltic pumping. It provides more accurate and more physical results for stream traces; pressure drops and velocities along the tube. A limited case of the study validates the theoretical and analytical results already presented in literature; hence the method is reliable. [ABSTRACT FROM AUTHOR]

The occurrence of vibration in engineering vehicles during operation is a common phenomenon, and the utilization of vibration-enhanced heat transfer serves as a viable approach to enhance the efficiency of heat transfer in radiators. This study designs a vibration test platform for heat exchangers to investigate the impact of different vibration parameters on heat transfer performance. Additionally, a fin vibration model is constructed using overlapping grid technology to simulate the behavior of flat fins under varying vibration conditions. Corrugated fins were chosen for investigation under vibration conditions, utilizing an orthogonal experimental approach to analyze the impact of fin structural parameters on heat exchanger performance. Findings indicate that vibration enhances the air side heat transfer coefficient of the heat exchanger, in experimental settings, the gas side heat transfer coefficient of the heat exchanger demonstrated a maximum increase of 12.28%. Simultaneously, vibration induces an escalation in pressure loss, with the maximum drop reaching 28.72%. The heat transfer factor j of the heat exchanger exhibits an augmentation in response to heightened vibration intensity, while they diminish with escalating speed. Furthermore, vibration alters the impact of structural factors of corrugated fins on heat transfer efficacy. During vibration, the sensitivity of fin height and wavelength intensifies, whereas the sensitivity of pitch and wave amplitude diminishes. The findings of this research offer valuable insights for further investigation into the heat transfer capabilities of fins under vibration.

This paper is a review of the literature about CFD modeling and analysis of journal, thrust, and aerostatic bearings; the advantages and disadvantages of each are specified, and the bearing problems that have been analyzed are discussed to improve their designs and performance. A CFD transient analysis of journal bearings was conducted using the dynamic mesh method together with movement algorithms while keeping a structured mesh of a good quality in the ANSYS Fluent software to determine the equilibrium position of the journal and calculate the dynamic coefficients. Finally, areas of opportunity for analyzing and designing fluid film bearings to improve their performance are proposed. [ABSTRACT FROM AUTHOR]

The investigation of cavitating trailing vortices emerging from marine propellers is of great interest in the industry. With the help of computational fluid dynamics (CFD), studying the cavitating trailing vortices may be facilitated. However, limitations in computational power raise the necessity to execute numerical simulations as efficiently as possible. The time-efficient simulation of cavitating trailing vortices interacting with rigid bodies is especially challenging due to the continuous change of cavity locations. This study investigates the usability, capability, and practicability of automatic adaptive refinement at every calculation time step for transient Reynolds-averaged Navier–Stokes (RANS) and large eddy CFD simulations of the cavitating tip and hub vortices, utilizing the Schnerr–Sauer cavitation model, in the presence of a rudder located in the propeller slipstream and for an isolated propeller, with additional focus on the computational effort necessary for using high frequency updating adaptive mesh refinement (AMR). It is found that AMR is suitable for resolving cavities with relative motion to the propeller and in interaction with slipstream obstacles. However, the computation time is significantly increased, which renders this method useful only if a classic AMR is not possible due to geometrical limitations. Even in the cases that benefit from the automated AMR, numerical instabilities may lead to unphysical pressure fluctuations, which reduce the suitability of the method for the evaluation of underwater radiated noise. [ABSTRACT FROM AUTHOR]

A recently developed launching device called the gun–track launch system is affected by its constrained track, such that the form of the muzzle jet changes from the state of free development in the entire space to a constrained state, where this lends unique characteristics of development to its flow field. In this study, the authors establish the corresponding model for numerical simulations based on the dynamic mesh method. We also considered a model of simulation of the muzzle jet with an "infinitely" constrained track to analyze its performance under real launch conditions to explore the mechanism of development and the disturbance-induced propagation of the shock wave when the muzzle jet impinges on moving bodies. The results showed that the muzzle jet exhibited a circumferential asymmetric shape that tilted toward the area above the muzzle and generated transverse air flow that led to the generation of a vortex on it. Because the muzzle was close to the ground, the jet was reflected by it to enhance the development and evolution of the shock waves and vortices and to aggravate the rate of distortion and asymmetry of the jet. The wave reflected from the ground was emitted once again when it encountered the infinitely constrained track. No local low-pressure area or a prominent vortex was observed after multiple reflections. Because the track in the test model was short, the waves reflected by the ground were not blocked, and vortices were formed in the area above the ground. Significant differences in the changes in pressure were also observed at key points in the domain. The results of a comparative analysis showed that the infinitely constrained track increased the Mach number of the moving body from 1.4 to 1.6. The work provides a theoretical basis and the requisite technical support for applications of the gun–track launch system. [ABSTRACT FROM AUTHOR]

High-speed elevator cars affected by external excitations exhibit complex horizontal vibration responses during their entire operating processes. To accurately explore the horizontal vibration response of a car and the response differences between the operating processes, a gas–solid coupling model for the entire high-speed elevator operating process was developed based on the finite volume method, Lagrange's theorem, and the external excitations obtained from dynamic mesh technology and the time-variant guideway excitation simulation method. The differences in the car's horizontal vibration acceleration and the effect of the fluid load disturbance during different high-speed elevator operating processes were analyzed by considering the different operating characteristics of the car during its acceleration–uniform speed–deceleration process. The feasibility of the model and modeling method were verified by testing an actual 7 m/s high-speed elevator. The results showed that the horizontal vibration acceleration of the car reached its maximum value during the uniform speed process, and the shaft fluid pressure load had the most significant effect on the horizontal vibration response of the car during the deceleration process. [ABSTRACT FROM AUTHOR]

Axial flow check valve (AFCV) is widely used in piping systems because of its small flow resistance, low noise, and good sealing performance. Its working performance directly affects the safety of the pump unit and the reliability of piping system. In the event that an accident occurs in piping systems, AFCV is closed to prevent backflow. However, rapid closing of the valve can cause the disk to exert a large impact load on the seat, which can affect the service life of the valve and the process safety of the system loop. Therefore, it is necessary to study the transient closing characteristics of AFCV with damping structure. The dynamic mesh technology is used to simulate the closing process of AFCV with different damping structures. The effects of the structures of damping devices as well as the diameter of damping holes on the dynamic motion, fluid force, and damping characteristics are analyzed, respectively. The results show that the damping structure with damping holes not only has better performance in slow closing and deceleration than the damping structure with annular gap but also reduces pressure fluctuation more effectively. Moreover, the fluid damping force generated by the damping structure with damping holes during the closing process is linear with the square of the velocity. Also, the correlation between impact velocity and the diameter of damping holes is obtained. The selection strategy of machining accuracy of damping holes is proposed. This work can provide a certain reference value for the design of AFCV in practical engineering, and it can also benefit safety and maintenance of piping system. [ABSTRACT FROM AUTHOR]

Most of the current research on heavy gas dispersion focuses on how fixed obstacles affect gas spreading. The turbulence caused by the movements of people or traffic will significantly affect heavy gas dispersion. Accordingly, this study presents an investigation of heavy gas dispersion under the influence of moving obstacles, which is based on the dynamic mesh approach using computational fluid dynamics (CFD). A turbulence model suitable for such a condition has been developed, and we have designed a small-scale experiment to verify the model's viability. Consequently, the verified model is further applied to a full-scale scenario for a chemical factory where a chlorine leak triggers an evacuation movement. On the basis of this scenario, we simplify the massive escape crowd to a regular geometric model, and the effects of the speed and size of movable obstacles on gas dispersion have been investigated by means of the RNG k-ε model and the layering updating approach in the dynamic mesh. [Display omitted] [ABSTRACT FROM AUTHOR]

Improving the output flow quality of the high-precision micro bidirectional gear pump can effectively improve the position control accuracy and dynamic characteristics of the electro-hydraulic actuator. In order to meet the appeal requirements and reduce the vibration and noise of the gear pump and prolong its working life, this paper starts with the research of the key part of the gear pump–the unloading groove structure. The three characteristics of trapped oil phenomenon, cavitation phenomenon, and flow were used as key indices to evaluate gear pump performance. Using numerical simulation analysis, the dynamic grid simulation method was used to explore the influence of unloading groove spacing on the transient multi-flow field characteristics of the gear pump under conventional design range. Our results show that reducing the distance between unloading grooves can greatly reduce the trapped oil pressure and the amount of gas precipitation in the flow field, while reducing flow pulsation and improving volumetric efficiency. However, when the unloading groove spacing is too small, the instantaneous flow curve loses the pulsation characteristics and the flow stability decreases. Considering the influence of the gear pump on the accuracy of the electro-hydraulic actuator and the performance of the gear pump itself, the analytic hierarchy process was used to obtain the 1 mm unloading slot spacing, which best meets the engineering requirements of high flow accuracy and low vibration noise. The results provide a basis for work on the structural optimization of high-precision micro gear pumps.

A hydrokinetic turbine with a vertical axis is specifically designed to harvest the kinetic energy from moving water. In this study, three vertical axis water turbines, namely Gorlov, Darrieus, and Savonius turbines, were compared for their efficiency via numerical modeling for steady-state conditions via the ANSYS 2022 R2 Fluent model. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) was implemented with an SST k-ω turbulence model. The dynamic mesh technique, which allows modeling according to changes in angular velocity at each time step, was used to simulate flow around the turbines for six different velocities (from 0.5 to 3 m/s). The efficiency of the turbines was compared and the results were analyzed. The pressure, velocity, and turbulence kinetic energy distributions around the rotor were measured at different rotational angles and results indicated a wider operating range for the Darrieus and Gorlov turbines compared to the Savonius turbine. The highest power coefficient of 0.293 was achieved in the model featuring a Darrieus turbine, corresponding to a TSR value of 1.34, compared to 0.208 for the Gorlov and 0.257 for the Savonius turbine, at TSR values of 1.3 and 1.06, respectively. Numerical modeling results pointed to a significantly higher self-starting capacity for the Savonius turbine compared to the others.

Pneumatic down-the-hole (DTH) hammer has been extensively used in air drillings through hard and ultra-hard geological formations. Numerical modeling can offer close observation on the working behaviors by visualizing internal pressure status as well as provide reliable performance predictions for large-diameter DTH hammers to which conventional empirical and experimental approaches cannot be applied. In this study, CFD simulations coupled with dynamic meshing are utilized to simulate the air flow and piston movement inside the large-diameter DTH hammers. The numerical modeling scheme is verified against a theoretical model published in literature. Effects of structural parameters on hammer performance, including piston mass, piston upper-end diameter, piston groove diameter, and lengths of intake and exhaust stroke in both front and rear chambers, are analyzed in detail by virtue of sets of numerical simulations. The simulations suggest that changing the intake stroke of front chamber has a negligible influence on hammer performance while increasing the piston groove would lower all the four indicators of hammer performance, including impact energy, impact frequency, maximum stroke, and air consumption rate. Changing the other structural parameters demonstrates mixed effects on the performance indicators. Based on the numerical simulations, a large GQ-400 DTH hammer has been designed for reduced air consumption rate and tested in a field drilling practice. The air drilling test with the designed hammer provided a penetration rate 1.7 times faster than that of conventional mud drilling. [ABSTRACT FROM AUTHOR]

In recent years, China has been building several inter-basin water conveyance projects across mountains and deep valleys, leading to the extensive use of long tunnels and inverted siphons. The dynamics of mixed free-surface-pressurized flows are critical for tunnel design and operational safety. However, traditional numerical computation schemes cannot precisely and efficiently capture the pressure interface because the tunnel may be more than 70 km long. This study aims to develop a hybrid scheme that is as fast as the large-time-step Preissmann four-point scheme (FDM) and has the approximate interface accuracy of the finite volume method (FVM) by dynamic grid meshing. A dynamic mesh domain model (DM) is proposed by adopting an FVM mesh with a small time step to dynamically capture the interface and applying an FDM mesh with a large time step to improve computational efficiency. The results show that the method can simulate flow patterns, such as transcritical and pressurized flows, by ignoring the acceleration convection terms and capturing mixed free-surface-pressurized flows conveniently, accurately and efficiently. Furthermore, it can accelerate the computational speed of the transient mixed flow by a factor of approximately 100 when the target tunnel length exceeds 1200 m. The proposed scheme cannot capture the water hammer pressure because of the large time step. However, it can be effectively utilized in large cascade water delivery systems where the flow changes gradually. [ABSTRACT FROM AUTHOR]

The present study investigates dust generated from the unloading process in a high-rise building for the mine hoist system and analyzes dust dispersion with the moving conveyance in the building. First, the gas-solid two-phase flow in the building was investigated based on the CFD-DPM method. In particular, the moving conveyance was considered in detail and treated via the dynamic mesh technology. Then, the airflow and dust distribution were investigated in the building. The airflow and the dust concentration at selected points show good agreement with the relative results of field measurements by ourselves. It is found that the descending conveyance significantly influences the surrounding flow field and the spatial and temporal distribution of dust. Dust concentration before the dust source (2 m × 2 m) is high, which extends downward with the conveyance. Dust concentration of the lower floors increases obviously when compared with that of the condition without the movement of the conveyance. The descending velocity of the conveyance also affects the amount of PM2.5 discharged from the return air outlet. The fitting functions are provided to predict PM2.5 emissions to the surrounding atmosphere. The research results are of great significance for the improvement of the dust control system for cleaner production technology. [ABSTRACT FROM AUTHOR]

Binder jetting is a crucial process in additive manufacturing (AM) and is widely used in sand mold casting. This study explores the challenges of simulating binder droplets in ANSYS Fluent, including complexity and computational time. To overcome these challenges, we propose a geometric approach that models the binder droplet as a circular shape instead of an actual droplet. Additionally, the dynamic mesh feature is employed to transform the initial boundary condition into a wall condition at a specified time interval (Δt). This simplified approach eliminates the need to simulate actual droplets, leading to significant computational resource and time savings. By adopting this geometric approach, we can accurately predict the diffusion and penetration behavior of binder droplets with varying materials and volumes in porous media with different porosities. Through data analysis, it was found that the main variables affecting the diffusion diameter and penetration depth are binder volume and porosity. The successful implementation of this simplified model enables researchers and engineers to expedite the simulation of binder behavior, facilitating process optimization and enhancing the understanding of binder jetting technology in the field of additive manufacturing. [ABSTRACT FROM AUTHOR]

Slot jet reattachment (SJR) nozzle is a novel nozzle design that overperforms the regular impingement nozzles or perforated plates for heat transfer and drying, heating or cooling applications of moist materials. The SJR nozzle is a viable design to dry fragile products such as food and paper. Mesh-type conveyor belts are commonly used in the food industry. There is a need for understanding how the SJR nozzle performs with mesh-type conveyor belts because prior studies have solely considered solid surfaces. Therefore, an extensive numerical study is performed to solve the flow field of the SJR nozzle with an exit angle of +45° on top of a mesh-type belt with and without products using COMSOL Multiphysics® without including heat transfer. Turbulent fluid flow is theoretically modeled using the k-ɛ turbulence model for the SJR nozzle. The numerical predictions are validated with experimental data for stationary surface. Six different cases are studied to capture the effects of the presence of products on the belt and the conveyor belt speed. Additionally, the presence of an SJR nozzle on the bottom of the belt with and without a lateral offset is studied. The mass flow rate escaping underneath the belt is compared to the total mass flow rate at the nozzle exit, shear stresses are compared at three different surface velocities, and maximum force magnitudes as product travels are reported. The results show that the flow can reattach to the product surface regardless of surface motion, but reattachment characteristics depend on product orientation with respect to the SJR nozzle. Although significant mass flow escapes through the belt, the presence of products mitigates this loss. In addition, doubling the belt speed increases the shear stresses applied by the surface and decreases the average mass flow loss. Also, an additional SJR nozzle on the bottom of the belt almost cancels this mass flow loss even when there is a lateral offset between the nozzles. [ABSTRACT FROM AUTHOR]

In computations of unsteady flow problems by the arbitrary Lagrangian–Eulerian (ALE) method, the introduction of the grid velocity in the transport terms of the governing equations is not a sufficient condition for conservativeness if topology changes in the dynamic mesh are present and the number of mesh cells changes. We discuss an extension to second-order time differencing schemes (Implicit Euler and Crank–Nicolson) in the finite volume framework, to achieve second-order time-accuracy of the solution. Numerical experiments are given to illustrate the effectiveness of the presented method. [ABSTRACT FROM AUTHOR]

Gas fuel control valves play important roles in the control of gas flow in high-precision gas turbines. To clarify the influence of coupling between the structure and the fluid system, a thermal fluid–solid coupling mechanism is presented based on numerical investigations carried out using a dynamic mesh technique. Valve core deformation can affect the outlet gas flow accuracy. At 2% valve opening, the gas temperature contributes 93% to the deformation. The effect of deformation on the flow accuracy at 6% valve opening and 4% valve opening is increased by 4.8% and 7.3%, respectively. The fluctuation range of the gas temperature and pressure in front of the valve should be strictly controlled to ensure the high precision and high stability of the outlet flow. These results help to clarify the processes that occur in the valve flow path, leading to the flow control instability observed in the control valve. [ABSTRACT FROM AUTHOR]