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Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency 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.)

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Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology 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.)

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Copyright of China Sciencepaper is the property of China Sciencepaper 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 China Sciencepaper is the property of China Sciencepaper 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 China Sciencepaper is the property of China Sciencepaper 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 Natural Gas Industry is the property of Natural Gas Industry Journal Agency 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 Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University 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 China Sciencepaper is the property of China Sciencepaper 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 Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology 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.)

In order to study the distribution of H2S gas diffusion flow field in different building layout, CFX computational fluid dynamics software was used to simulate the H2S gas diffusion flow field under seven different building layout conditions in this paper. Furthermore, an example of verification was presented based on the building complex of a natural gas purification plant. The conclusions were listed as follows:(1) the stagnant area of gas velocity is closely related to the building layout, and the dead zone often occurs on the leeward side of the buildings while the air velocity would increase at the gap between the buildings; (2) the larger the width of the windward side of buildings is, the greater the stagnant area and area of leeward side of buildings are; (3) the CFX could be applied to simulate the air flow movement in complex building layout properly and provided a theoretical basis for the establishment of escape route after H2S gas leakage accident. [ABSTRACT FROM AUTHOR]

The detection chamber is an important part of the bionic olfactory detection analysis instrument. Unreasonable structure design of detection chamber can cause gas vortex and prolong the sensors' response and recovery time. Non-uniform distribution of airflow field can cause inconsistence of the sensor array in numerical induction. Therefore, it is significant to explore the characteristics of gas flow and distribution, optimize the flow field structure, improve the uniformity and stability of the flow rate and advance the accuracy and repeatability of olfactory detection chamber. However, the traditional method of further manufacture design improvements requires long transformation time, and high costs, and the measurement range is usually disappointing. Computational Fluid Dynamics (CFD) can provide detailed information on airflow simulation and ensure convenient design of agricultural equipments. In order to optimize the structure of bionic olfactory detection chamber of sweeping type, and improve the uniformity and stability of fluid velocity distribution, based on the differential equations of fluid motion, the internal flow field of olfactory detection chamber was numerically simulated by using the CFD. This paper proposed the models of 3 types of chamber detection original structures, and the uniformity and stability of olfactory sensors' detection area from the optimal model were compared with the test results. The 3 types of detection chamber original structures were linear arrangement, parallel arrangement and structure of multi nasal ducts. Each model design was mainly composed of an intake pipe, a detection chamber, a sensor array and a vent pipe. The fluid flow rate was much smaller than the acoustic velocity and the fluid flow was considered as an incompressible process inside the chamber. In the process of olfactory detection, the fluid flowed into the detection chamber from the intake pipe and flowed out of the vent pipe, so the inlet boundary was set to velocity inlet. Outlet pressure boundary conditions were selected, and the natural pressure was taken as the boundary value. The fluid temperature in the chamber was room temperature which was 26 ℃. The wall had no slip boundary condition, and was assumed to be a rigid wall without considering the influence of wall elasticity. The speed deviation ratio and the nonuniformity coefficient were chosen as comprehensive evaluation indicators. The velocity distribution in chamber flow field was obtained and used to analyze the original structures to provide the preference design. The detection chamber of multi nasal ducts corresponded to inclination model. The simulation results indicated that the structures of detection chamber influenced air velocity distribution. The detection chamber of multi nasal ducts along the pipe axis (0.035-0.049 m range) had a velocity smooth region, the velocity of which was stabilized merely at 0.018-0.268 m/s, which could meet the requirement of detection condition. There were no velocity smooth regions in the linear arrangement, and the airflow velocity of smooth regions in parallel arrangement merely ranged from 0.001 to 0.018 m/s. The detection chamber of multi nasal ducts showed the advantage in the uniform and stability of velocity, of which the maximum values of speed deviation ratio and nonuniformity coefficient were calculated to be 0.830 6 and 0.292, respectively. Meanwhile, in the gas detection period by the numerical simulation, the detection time of 3 models was 223.4, 302.0 and 213.8 s, respectively, and the minimum value of the structure of multi nasal ducts showed that it had fast flow response and high working efficiency. Moreover, the optimum structure could effectively improve the consistency of the sensors' numerical detection, and the standard deviation and the coefficient of variation ranged from 0.153 5 to 0.428 3 and from 0.030 5 to 0.082 7, respectively. The results provide a reference for the uniformity design of flow field structures similar to the detection chamber. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Jiangsu University (Natural Science Edition) / Jiangsu Daxue Xuebao (Ziran Kexue Ban) is the property of Editorial Department of Journal of Jiangsu University (Natural Science Edition) 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.)

In order to evaluate the performance prediction accuracy of single-channel pump under computational fluid dynamics, a single-channel pump was taken as the study object. The standard k-ε, RNG k-ε (renormalization group k-ε), standard k-ω and SST k-ω (shear stress transport k-ω) were used to predict the performance of single-channel pump numerically. Meanwhile the grid dependence was checked by employing 5 sets of meshes to improve the computational accuracy. The results of steady and unsteady numerical simulation were compared with that of the experiment on the head and efficiency. The unsteady results were closer to the experimental value. Therefore, the unsteady simulation method should be applied to simulate the internal flow of the single-channel pump. The head, efficiency and power were predicted under 3 different discharges (0.6 Qd, 1.0 Qd, 1.4 Qd, Qd is flow rate on design operating conditions, 220 m3/h) by using CFX (computational fluid dynamics X) 14.0. Energy performance prediction error was analyzed by compared with experimental results. The results showed that there was different degree error between the performance prediction values of the different turbulent models and experimental values. For head prediction of the discharge of 0.6Qd, the standard k-ω model, compared with the other 3 models, had higher prediction accuracy and the head error was 0.008%, followed by the SST k-ω model. However, for efficiency prediction of the discharge of 0.6 Qd, the SST k-ω model had the minimum error value. Therefore, for the simulations at low flow rates, head, efficiency and power errors were 0.38%, 3.12 percentage points and 5.59% respectively with the SST k-ω model. At the design condition, while the head calculation results of the RNG k-ε model were closer to the experimental results than other turbulent models, the standard k-ε model got the best results for the efficiency calculation. The efficiency error of the RNG k-ε model was about 0.1 percentage points lower than the standard k-ε model, so the RNG k-ε model was applied to performance prediction under the design operating condition. When the single-channel pump was operating at the large flow condition (1.4Qd), the RNG k-ε model possessed the highest precision of the head prediction and the standard k-ε model was the best in the efficiency prediction. For comprehensive evaluation of the data, among all 4 turbulent models the RNG k-ε model was the best one to predict the performance of single-channel pumps at the large flow rate. For the internal flow simulation of single-channel pump, the flow separation existed on the blade pressure surface under various operating conditions. As the decrease of the flow rate, the flow near the inlet edge tended to be disordered, especially with a wide range of backflow at the low flow rate. At the same time, there was large backflow on interior areas of the blade pressure surface. There were stagnation points near the inlet edge of blade suction surface and on the backboard. However, serious separation and recirculation flow would occur within the flow passage of the blade pressure side under the low flow conditions. Low pressure on the ring surface of impeller outlet was upstream to the blade outlet and near the outlet. The conclusions in this paper will provide a reliable performance prediction data and practice basis for the single-channel pump, also point the way for developing turbulent models for further study of single-channel pumps. [ABSTRACT FROM AUTHOR]

Belt dryers are the most popular equipment for betel nut drying. One of the drawbacks of this dryer is the non-uniformity in the desired moisture content of end product. In order to improve the structure of flow field and the moisture uniformity for the belt dryer, on the theoretical basis of computational fluid dynamics, the effects of the accumulative thickness, air velocity, air temperature and moisture content of hot air on the moisture uniformity of betel nut dried were simulated and discussed by using FLUENT software package. The orthogonal table about 4 factors and 3 levels was designed. In this paper, the betel nut was considered to be a wet porous medium, and the air flow through the areca layer was seen as the flow inside the porous medium, as well as the flow in the layer. By adding momentum equation source term to the momentum equation, the porous medium model was formed. The momentum equation was divided into 2 parts which included viscous item loss and inertia item loss. Experimental verification was carried out. Experimental test was finished in a multilayer belt dryer designed by Hunan Chain Co. Ltd.. The dryer was a five-layer mesh belt with cross flow drying system. Observation hole was set in the 1st path (top layer) and the 5th path (bottom layer), and the hole position was X=0.8, 2.4, 4.0, 5.6, 7.2 m, respectively. After washing, soaking, air-curing, separating, removing the film, rinsing and draining, betel nut was dried in dryer. The QDF-2B hot ball type electric wind speed meter was set to test the wind speed of the dryer, and the measured data had a good agreement with the calculation results. Based on the Shannon-Wiener index, the water content uniformity index was put forward, which was compared to the conventional index and the calculation result. Two deflectors with different shape (traditional deflector and wing-shape deflector) were put forward and analyzed. Simulation results showed that in the length direction of top path, the wind speed at the positions of X=4 m and X=6 m was relatively larger, which was 0.8 and 0.7 m/s respectively. The wind speed when X was equal to 4-6 m was gradually reduced, while that when X was equal to 4.5-5.5 m was the lowest (0.4 m/s). The wind speed curve had the “camel peak” shape. In the length direction of bottom path, the hot air was divided into 2 parts, most of which flowed along the length direction, and the remaining moved upward through the material layer. The speed was gradually reduced in bottom channel, and the speed through the material layer was maintained above 1.05 m/s. Results showed that the moisture content of the betel nut layer with a thickness of 80 mm was more uniform than 40 or 60 mm. Therefore, the thickness of betel nut had most effect on the uniformity of moisture content than the other 2 factors. The general trends of water content uniformity index, conventional index and “camel peak” curves were similar, but that of the water content uniformity index was more close to the calculation result. It indicated that layer thickness of 80 mm, inlet temperature of 70 ℃, flow rate of 1.5 m/s, moisture content of 0.24 were more conducive to moisture uniformity. The deflector could obviously improve the uniformity of moisture. Installing simple deflector mildly expanded the contact area of air inlet and slightly reduced the moisture of betel nut, yet there still had partial areas without drying. These areas were mainly distributed in the middle and sides of the dryer. After equipping with wing deflector at the entrance of dryer, hot air was evenly distributed to the entire first path, while moisture content of the betel nut layer decreased from 0.285 to 0.215, and moisture uniformity was improved. In the case of shortening the drying time by 5 min, the water content uniformity index was 0.926, and the drying efficiency was promoted. [ABSTRACT FROM AUTHOR]

High order accuracy numerical simulations for flows of high lift trapezoidal wing configuration were performed by solving Navier-Stokes equation together with SST two-equation turbulence model. In the study, WCNS-E-5 scheme was utilized in the discretization of convection terms, while 6th order central difference scheme for viscous term. Grid convergence result was obtained, which was in good agreement with test data, and WCNS scheme was less dependent on mesh density than 2nd order scheme. Compared with other computational results obtained by typical CFD solvers, both the force coefficients and the surface pressure distributions given in this paper shown better accordance with the test data, and more reasonable prediction of flow structure near stalling was obtained. As revealed from these results, WCNS scheme took higher accuracy order and was more suitable for simulation of flow around high lift configurations than 2nd order scheme. The capability and the robustness of the program to simulate complex high lift configurations were confirmed. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) gradually plays an important role in the evaluation of the wind tunnel design project. This paper is about the evaluation results of the slotted test section of 0.6m x 0.6m continuous transonic wind tunnel including alternative design and flow field quality, especially comparing full slot with half slot. It presents the control equations and boundary conditions for numerical simulation firstly. Then the details of numerical results about the high subsonic and low supersonic flow characteristic are given. The length of velocity uniformity region and velocity deflection angle meet the design accuracy and that proved the rationality. The half slot project was better than the full one at high subsonic. Low supersonic field could be achieved when air was bleed from plenum chamber. However, more bleed air rate, shorter length of velocity uniformity region. Full slot project had less disorder on flow of the plenum chamber than the half. Further investigation on the flow mechanism of re-entry flaps indicated that the flow was unsteady one significantly. [ABSTRACT FROM AUTHOR]

CFD method has the advantage of well simulating the flow over wind farm of complex terrain, compared with the method of using the software WAsP with linear model, thus becoming the development direction of assessment of wind resources in complex terrain. In order to use the CFD package FINE/TURBO and standard k-ε turbulence model with wall function in the wind resources assessment and micrositing of wind farm in the complex terrain, in this paper, Island Nanao had been simulated in wind directions at intervals of 30 degrees, under the assumption of neutral condition, to investigate the influence of inlet condition on the results. The simulation results show that the wind speed-up and intensity don't change essentially under different inlet conditions. Based on this law, with whole year wind data, an assessment method with post processing has been built, providing a strong reference for engineering practice. [ABSTRACT FROM AUTHOR]

The paper presents a methodology for calculating the unsteady aerodynamic forces characteristics and gust response of the unmanned air vehicle (UAV) model using computational fluid dynamics (CFD) tools, and the efficiency of gust alleviation based on direct force control are also studied. Based on unsteady Euler equations, dynamic responses in vertical gust flow perturbation are investigated. The grid velocity method, which is used to model unsteady flow via grid movement, is introduced to simulate the gust influence. This approach avoids numerical instabilities and decouples the step change in the angle of attack from a pitch rate. And the dynamic chimera grid method is used to simulate the rudder movement of the gust alleviation effect. Numerical results for the NACA0006 airfoil are validated by comparison with analytical results for two dimensional indicial responses. The initial and final lift values of the indicial responses closely match the exact analytical values as given by piston theory and quasi steady thin airfoil theory respectively. The solutions at small times match quite closely the exact solution which is known only for small times given by linear theory. The application of the same method to the UAV model reveals important characteristics of the three-dimensional vertical discrete gust response for the One-minus-cosine gust profile and gusts cause step changes in the angle of attack, and important characteristics of the gust response and resulting flow features are explained. Furthermore, the flow perturbations under dynamic rudder motion are investigated using moving chimera grid technique. Our study shows that with certain designed motions, the flapping rudder can effectively alleviate the freestream gust fluctuation and ensure a stable flight. However, no single parameter can determine whether the flapping rudder can reduce the gust effect. Finally, unsteady aerodynamic loads are computed for the wing of model with the designed rudder motion, the significance of the gust propagation effects is shown. It is found that the direct calculation of the gust response using CFD gives quite accurate results and provides a rich database. In general, this paper shows that the well-designed rudder movement can effectively alleviate the freestream gust fluctuation and ensure high flight qualities. [ABSTRACT FROM AUTHOR]

As the aerodynamic forces are inconvenient to be measured in the wind tunnel tests of rain-wind-induced vibration (RWIV) of a stay cable under artificial simulation of rainfall, this paper presents a hybrid approach combining experiment anti computational fluid dynamics (CFD) numerical simulation for RWIV of a stay cable. The stay cable (including the rivulet) and the flow field are considered as two substructures in the entire system, and the motions of stay cable and rivulet measured through wind tunnel tests are considered as known boundary condition and applied to the flow field. The flow around the moving boundary is then numerically simulated by the Fluent CFD code. First, the feasibility and precision of this approach are verified through the vortex-induced vibration of a circular cylinder, and then the approach is used to study the RWIV of the stay cable. The transient aerodynamic lift and drag coefficients are calculated and applied to a single degree of freedom model (SDOF) of the stay cable. The comparison is carried out between the oscillation responses of the SDOF model and experimental results, which indicate that the hybrid approach combining experiment and CFD numerical simulation can effectively simulate the transient aerodynamic coefficients of stay cable suffering from the RWIV. [ABSTRACT FROM AUTHOR]

A computational study performed for an artillery projectile using finite volume TVD schemes is described in this paper. First, computed Magnus moment coefficients for the spinning projectile have been compared with the available experimental data of SOCBT at Mach 3 and are found to be generally in good agreement. The results demonstrate that the method can provide an accurate and viable approach for this problem. Then, computational fluid dynamics (CFD) modeling and analysis of the spinning projectile with fixed canard have been conducted to determine the longitudinal aerodynamic coefficients. The analyses provide a detailed understanding of the effects of canard with different circumferential position on longitudinal aerodynamic coefficients at three supersonic speeds and various angles of attack. [ABSTRACT FROM AUTHOR]