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高洪时期非常规流速仪法测流的探讨 被引量:2
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作者 雷庆 王占兴 于丽玲 《黑龙江水专学报》 2006年第1期89-91,共3页
提出了采用普通吊车悬吊流速仪和冲锋舟动船测流的高洪时期测流的方法,并与常规测流方法进行了对比分析和误差分析,证实了方法的可行性。
关键词 非常速仪测 冲锋舟动船测 普通吊车悬吊速仪测
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无后效非平稳Poisson型流的特性
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作者 黄启亮 《广东第二师范学院学报》 1999年第3期55-58,共4页
在综述关于无后效非平稳Poisson型流的两个重要结果[3]的同时,将流的概念精确化,把流看作是个具有某些特性的随机过程;对上述两个结果的表述与证明,都作了补充与改进.文中两个定理较深刻地刻划了无后效非平稳poisson型流的特性.
关键词 Poisson型 普通 无后效 平稳 非常流 主导函数 正规
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ENHANCED UNSTEADY AND NONLINEAR ROTOR WAKE MODEL FOR REAL-TIME FLIG HT SIMULATION 被引量:2
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作者 孙传伟 高正 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2003年第1期12-16,共5页
WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be pr... WT5 'BZThis paper presents an unsteady and nonlinear wake model based on th e widely used Peters He finite state dynamic wake model with improvements. The swirl component in the tip trace plane (TTP) can be predicted, nonlinear items are added into the linear theory, and the old small angle assumption use d in matrix prediction is removed. All of these enha ncements are aimed at the low speed flight phase and formulations for the induce d velocity field just in the TTP frame are derived. The corresponding FORTRAN pr ogram is tested and optimized for the real time applications on PCs. 展开更多
关键词 HELICOPTER ROTOR WAKE dynamics inflow
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EXPERIMENTAL STUDY ON DARCY′S LAW IN HELE-SHAW CELLS 被引量:1
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作者 孙建红 许金造 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2003年第2期134-139,共6页
The basic physics of unsteady Hele-Shaw flow at high Reynolds numbers is mainly studied by an experimental measurement. In order to confirm the Darcy′s law in Hele-Shaw cell, since there is an analogy between flow in... The basic physics of unsteady Hele-Shaw flow at high Reynolds numbers is mainly studied by an experimental measurement. In order to confirm the Darcy′s law in Hele-Shaw cell, since there is an analogy between flow in cells and that in porous media, progressive water waves are utilized to build an unsteady flow in a Hele-Shaw cell, and which complex wave number is measured by a wave height gauge. Meanwhile, theoretical analyses are used to compare with experimental data. Result shows Darcy′s Law is not exactly correct for unsteady Hele-Shaw flows, and it is expected to conduct a modified Darcy′s Law. 展开更多
关键词 Hele-Shaw cell surface water wave Darcy′s law
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GRIDLESS METHOD FOR UNSTEADY VISCOUS FLOWS
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作者 蒲赛虎 陈红全 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2012年第1期1-8,共8页
Gridless method is developed for unsteady viscous flows involving moving boundaries. The point distri- bution of gridless method is implemented in an isotropic or anisotropic way according to the features of viscous f... Gridless method is developed for unsteady viscous flows involving moving boundaries. The point distri- bution of gridless method is implemented in an isotropic or anisotropic way according to the features of viscous flows. In the area far away from the body, the traditional cloud of isotropic points is used, while in the adjacent area, the cloud of anisotropic points is distributed. In this way, the point spacing normal to the wall can be small enough for simulating the boundary layer, and meanwhile, the total number of points in the computational do- main can be controlled due to large spacing in other tangential direction through the anisotropic way. A fast mov- ing technique of clouds of points at each time-step is presented based on the attenuation law of disturbed motion for unsteady flows involving moving boundaries. In the mentioned cloud of points, a uniform weighted least- square curve fit method is utilized to discretize the spatial derivatives of the Navier-Stokes equations. The pro- posed gridless method, coupled with a dual time-stepping method and the Spalart-Allmaras turbulence model, is implemented for the Navier-Stokes equations. The computational results of unsteady viscous flows around a NLR7301 airfoil with an oscillating flap and a pitching NACA0012 airfoil are presented in a good agreement with the available experimental data. 展开更多
关键词 gridless method cloud of points Navier-Stokes equations unsteady flow viscous flow
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Numerical simulation and analysis of solid-liquid two-phase threedimensional unsteady flow in centrifugal slurry pump 被引量:16
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作者 吴波 汪西力 +1 位作者 LIU Hui 徐海良 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第8期3008-3016,共9页
Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of... Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump. 展开更多
关键词 slurry pump solid-liquid two-phase flow unsteady flow 3-D full passage numerical simulation
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Numerical computation and analysis of unsteady viscous flow around autonomous underwater vehicle with propellers based on sliding mesh 被引量:4
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作者 高富东 潘存云 韩艳艳 《Journal of Central South University》 SCIE EI CAS 2012年第4期944-952,共9页
The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment, which realizes the nmlti-motion modes of the autonomous underwater vehicle (AUV) such as vectored thruster and wheele... The flexible transmission shaft and wheel propeller are combined as the kinetic source equipment, which realizes the nmlti-motion modes of the autonomous underwater vehicle (AUV) such as vectored thruster and wheeled movement. In order to study the interactional principle between the hull and the wheel propellers while the AUV navigating in water, the computational fluid dynamics (CFD) method is used to simulate numerically the unsteady viscous flow around AUV with propellers by using the Reynolds-averaged Navier-Stokes (RANS) equations, shear-stress transport (SST) k-w model and pressure with splitting of operators (PISO) algorithm based on sliding mesh. The hydrodynamic parameters of AUV with propellers such as resistance, pressure and velocity are got, which reflect well the real ambient flow field of AUV with propellers. Then, the semi-implicit method for pressure-linked equations (SIMPLE) algorithm is used to compute the steady viscous flow field of AUV hull and propellers, respectively. The computational results agree well with the experimental data, which shows that the numerical method has good accuracy in the prediction of hydrodynamic performance. The interaction between AUV hull and wheel propellers is predicted qualitatively and quantitatively by comparing the hydrodynamic parameters such as resistance, pressure and velocity with those from integral computation and partial computation of the viscous flow around AUV with propellers, which provides an effective reference to the shady on noise and vibration of AUV hull and propellers in real environment. It also provides technical support for the design of new AUVs. 展开更多
关键词 computational fluid dynamics sliding mesh wheel propeller autonomous underwater vehicle viscous flow field
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Comparisons between unsteady sediment-transport modeling 被引量:2
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作者 Lahouari Benayada Mahmoud Hasbaia 《Journal of Central South University》 SCIE EI CAS 2013年第2期536-540,共5页
The comparative study between unsteady flow models in alluvial streams shows a chaotic residue as for the choices of a forecasting model. The difficulty resides in the choice of the expressions of friction resistance ... The comparative study between unsteady flow models in alluvial streams shows a chaotic residue as for the choices of a forecasting model. The difficulty resides in the choice of the expressions of friction resistance and sediment transport. Three types of mathematical models were selected. Models of type one and two are fairly general, but require a considerable number of boundary conditions, which related to each size range of sediments. It can be a handicap during rivers studies which are not very well followed in terms of experimental measurements. Also, the use of complex models is not always founded. But then, the model of type three requires a limited number of boundary conditions and solves only a system of three equations at each time step. It allows a considerable saving in calculating times. 展开更多
关键词 friction resistance bed load suspended load mobile-bed modeling
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Statistical analysis of pressure fluctuations during unsteady flow for low-specific-speed centrifugal pumps 被引量:3
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作者 裴吉 王文杰 袁寿其 《Journal of Central South University》 SCIE EI CAS 2014年第3期1017-1024,共8页
A three-dimensional transient numerical simulation was conducted to study the pressure fluctuations in low-specific-speed centrifugal pumps. The characteristics of the inner flow were investigated using the SST k-ω t... A three-dimensional transient numerical simulation was conducted to study the pressure fluctuations in low-specific-speed centrifugal pumps. The characteristics of the inner flow were investigated using the SST k-ω turbulence model. The distributions of pressure fluctuations in the impeller and the volute were recorded, and the pressure fluctuation intensity was analyzed comprehensively, at the design condition, using statistical methods. The results show that the pressure fluctuation intensity increases along the impeller streamline from the leading edge to the trailing edge. In the impeller passage, the intensity near the shroud is much higher than that near the hub at thc inlet. However, the intensity at the middle passage is almost equal to the intensity at the outlet. The pressure fluctuation intensity is the highest at the trailing edge on the pressure side and near the tongue because of the rotor-stator interaction. The distribution of pressure fluctuation intensity is symmetrical in the axial cross sections of the volute channel. However, this intensity decreases with increasing radial distance. Hence, the pressure fluctuation intensity can be reduced by modifying the geometry of the leading edge in the impeller and the tongue in the volute. 展开更多
关键词 TRANSIENT pressure fluctuation intensity STATISTICS low specific speed centrifugal pump
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Characteristics of unsteady flow in porous media while considering threshold pressure gradient with Green's function 被引量:2
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作者 曹仁义 陈岭 +2 位作者 Y.Zee Ma 刘雪莹 于柏慧 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第1期201-208,共8页
The flow behavior in porous media with threshold pressure gradient(TPG) is more complex than Darcy flow and the equations of motion, and outer boundary and inner boundary with TPG are also different from Darcy flow fo... The flow behavior in porous media with threshold pressure gradient(TPG) is more complex than Darcy flow and the equations of motion, and outer boundary and inner boundary with TPG are also different from Darcy flow for unsteady flow of a producing well in a reservoir. An analytic method to solve this kind of problem is in a need of reestablishment. The classical method of Green's function and Newman product principle in a new way are used to solve the unsteady state flow problems of various shapes of well and reservoir while considering the TPG. Four Green's functions of point, line, band and circle while considering the TPG are achieved. Then, two well models of vertical well and horizontal well are built and simultaneously the function to calculate the moving boundary of each well model is provided. The results show that when considering TPG the pressure field is much different, which has a sudden pressure change, with a moving boundary in it. And the moving boundary of each well model increases with time but slows down rapidly, especially when the TGP is large. 展开更多
关键词 non-Darcy flow Green's function moving boundary threshold pressure gradient (TPG)
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A CFD Based Investigation of the Unsteady Hydrodynamic Coefficients of 3-D Fins in Viscous Flow 被引量:3
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作者 Nazir Zulfiqar 苏玉民 王兆立 《Journal of Marine Science and Application》 2010年第3期250-255,共6页
The motion of the fins and control surfaces of underwater vehicles in a fluid is an interesting and challenging research subject.Typically the effect of fin oscillations on the fluid flow around such a body is highly ... The motion of the fins and control surfaces of underwater vehicles in a fluid is an interesting and challenging research subject.Typically the effect of fin oscillations on the fluid flow around such a body is highly unsteady, generating vortices and requiring detailed analysis of fluid-structure interactions.An understanding of the complexities of such flows is of interest to engineers developing vehicles capable of high dynamic performance in their propulsion and maneuvering.In the present study, a CFD based RANS simulation of a 3-D fin body moving in a viscous fluid was developed.It investigated hydrodynamic performance by evaluating the hydrodynamic coefficients (lift, drag and moment) at two different oscillating frequencies.A parametric analysis of the factors that affect the hydrodynamic performance of the fin body was done, along with a comparison of results from experiments.The results of the simulation were found in close agreement with experimental results and this validated the simulation as an effective tool for evaluation of the unsteady hydrodynamic coefficients of 3-D fins.This work can be further be used for analysis of the stability and maneuverability of fin actuated underwater vehicles. 展开更多
关键词 oscillating 3-D fin RANS hydrodynamic performance viscous flow
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Experimental Study on Calculation of Hydro-Geological Parameters for Unsteady Flow 被引量:1
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作者 熊春宝 陈雯 叶作安 《Transactions of Tianjin University》 EI CAS 2013年第5期351-355,共5页
After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coeffici... After the linear analytical method of unsteady flow theory is further improved,an innovative and faster algorithm is introduced.The water storage in a confined aquifer is derived from the water transmissivity coefficient and the water-pressure conductivity coefficient.The water transmissivity coefficient is approximated by a Taylorseries expansion of drawdown,and the water-pressure conductivity coefficient is obtained by the average drawdown.In this algorithm,the distance of the observation points from the pumping well must be short.When the distance is as short as the radius of the main pumping well,the data of the drawdown difference between the sidewall and the center of pumping well are difficult to measure,but the same results can be achieved based on the assumption that the drawdown difference approximates to the drawdown of the observation wells at a radial distance from the pumping well according to the algorithm.Without the help of charts,this algorithm is more concise and efficient,which has been verified by the test of water pumping project in Tianjin Binhai International Airport. 展开更多
关键词 pumping test unsteady flow theory improved linear analytical method hydro-geological parameter
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Analysis of unsteady supercavitating flow around a wedge
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作者 隗喜斌 于开平 +2 位作者 邹平华 邹经湘 杨洪澜 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2009年第3期431-435,共5页
Supercavitating flow around a slender symmetric wedge moving at variable velocity in static fluid has been studied. Singular integral equation for the flow has been founded through distributing the sources and sinks o... Supercavitating flow around a slender symmetric wedge moving at variable velocity in static fluid has been studied. Singular integral equation for the flow has been founded through distributing the sources and sinks on the symmetrical axis. The supereavity length at each moment is determined by solving the singular integral equation with finite difference method. The supercavity shape at each moment is obtained by solving the partial differential equation with variable coefficient. For the case that the wedge takes the impulse and uniformly variable motion, numerical results of time history of the supercavity length and shape are presented. The calculated results indicate that the shape and the length of the supercavity vary in a similar way to the case that the wedge takes variable motion, and there is a time lag in unsteady supercavitating flow induced by the variation of wedge velocity. 展开更多
关键词 unsteady supercavitating integral equation method finite difference method time lag
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State Descomposition of Superprocesses of Stochastic Flows
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作者 ZHAO Qiao-ling LIU Xiao-shu YAN Guo-jun 《Chinese Quarterly Journal of Mathematics》 CSCD 北大核心 2006年第3期406-415,共10页
In this paper, we reconstruct the superprocesses of stochastic flows by martingale method, and prove that if and only if the infinitesimal particles never hit each other, then atomic part and diffuse part of this kind... In this paper, we reconstruct the superprocesses of stochastic flows by martingale method, and prove that if and only if the infinitesimal particles never hit each other, then atomic part and diffuse part of this kind of superprocesses will be also superprocesses of stochastic flows. This result completely answers the open problem in . 展开更多
关键词 SUPERPROCESSES stochastic flows martingale method martingale problem state decomposition
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Unsteady RANS and detached eddy simulation of the multiphase flow in a co-current spray drying
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作者 Jolius Gimbun Noor Intan Shafinas Muhammad Woon Phui Law 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2015年第9期1421-1428,共8页
A detached eddy simulation(DES) and a k-ε-based Reynolds-averaged Navier–Stokes(RANS) calculation on the co-current spray drying chamber is presented. The DES used here is based on the Spalart–Allmaras(SA) turbulen... A detached eddy simulation(DES) and a k-ε-based Reynolds-averaged Navier–Stokes(RANS) calculation on the co-current spray drying chamber is presented. The DES used here is based on the Spalart–Allmaras(SA) turbulence model, whereas the standard k-ε(SKE) was considered here for comparison purposes. Predictions of the mean axial velocity, temperature and humidity profile have been evaluated and compared with experimental measurements. The effects of the turbulence model on the predictions of the mean axial velocity, temperature and the humidity profile are most noticeable in the(highly anisotropic) spraying region. The findings suggest that DES provide a more accurate prediction(with error less than 5%) of the flow field in a spray drying chamber compared with RANS-based k-ε models. The DES simulation also confirmed the presence of anisotropic turbulent flow in the spray dryer from the analysis of the velocity component fluctuations and turbulent structure as illustrated by the Q-criterion. 展开更多
关键词 Drying Turbulence Two-phase flow CFD Detached eddy simulation Modelling strategy
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Developing Spline Based Overset Grid Assembling Approach and Application to Unsteady Flow Around a Moving Body
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作者 Hiroshi Kobayashi Yoshiaki Kodama 《Journal of Mathematics and System Science》 2016年第9期339-347,共9页
Overset or Chimera grid approach is one of methods to cope with complex geometries. A spline based overset grid assembling system has been developed. The system is based on structured grid approach and covers comprehe... Overset or Chimera grid approach is one of methods to cope with complex geometries. A spline based overset grid assembling system has been developed. The system is based on structured grid approach and covers comprehensive features for overset assembling, i.e., grid generation, grid modification, and computing Domain Connectivity Information (DCI) for overset interpolation. Ferguson spline curve is used to compute curves through grid points and cell centers for trimming grids and computing DCI robustly and accurately. Flow simulation around Kriso Container Ship (KCS) with jointed grids shows good continuity of flow field between the grids. The overset grid assembling is enhanced to unsteady problem as dynamic overset approach coupled with a solver which also has been developed in National Maritime Research Institute, Japan. Computed results for pitchup spheroid are compared with measured data and show good agreement in unsteady force acting on the spheroid. It is confirmed that the system has capability to simulate flow field around jointed grids and unsteady flow with dynamic overset assembling approach practically. 展开更多
关键词 Overset Assembling Dynamic Overset Unsteady Flow
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A New Differential Quadrature Methodology Based on Bernstein Polynomials for Solving the Equations Governing the Unsteady Flow of a Polytropic Gas
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作者 Abdul-Sattar J. A1-Saif Firas A. Al-Saadawi 《Journal of Physical Science and Application》 2015年第1期38-47,共10页
Aims of this paper are to improve ADI differential quadrature method (ADI-DQM) based on Bernstein polynomials and add a new application to the differential quadrature method. By using the new methodology, the numeri... Aims of this paper are to improve ADI differential quadrature method (ADI-DQM) based on Bernstein polynomials and add a new application to the differential quadrature method. By using the new methodology, the numerical solutions of the governing equations of unsteady two-dimensional flow of a polytropic gas are investigated. The numerical results reveal that the new technique is very effective and gives high accuracy, good convergence and reasonable stability. 展开更多
关键词 Differential quadrature method polytropic gas Bemstein polynomial ADI accuracy.
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Dual solutions of MHD stagnation point flow and heat transfer over a stretching/shrinking sheet with generalized slip condition 被引量:3
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作者 ABBAS Zaheer MASOOD Tahmina OLANREWAJU Philip Oladapo 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第6期2376-2384,共9页
An analysis was made to study the steady momentum and heat transfer characteristics of a viscous electrically conducting fluid near a stagnation point due to a stretching/shrinking sheet in the presence of a transvers... An analysis was made to study the steady momentum and heat transfer characteristics of a viscous electrically conducting fluid near a stagnation point due to a stretching/shrinking sheet in the presence of a transverse magnetic field and generalized slip condition. Two flow problems corresponding to the planar and axisymmetric stretching/shrinking sheet were considered. By means of similarity transformations, the obtained resultant nonlinear ordinary differential equations were solved numerically using a shooting method for dual solutions of velocity and temperature profiles. Some important physical features of the flow and heat transfer in terms of the fluid velocity, the temperature distribution, the skin friction coefficient and the local Nusselt number for various values of the controlling governing parameters like velocity slip parameter, critical shear rate, magnetic field, ratio of stretching/shrinking rate to external flow rate and Prandtl number were analyzed and discussed. An increase of the critical shear rate decreases the fluid velocity whereas the local Nusselt number increases. The comparison of the present numerical results with the existing literature in a limiting case is given and found to be in an excellent agreement. 展开更多
关键词 dual solutions stagnation-point MHD flow slip condition heat transfer numerical solution transverse magnetic fields
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Numerical Study of Unsteady Behavior of Partial Cavitation on Two Dimensional Hydrofoils
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作者 Md. Nur-E-Mostafa Md. Mashud Karim Md. Manirul Alam Sarker 《Journal of Shipping and Ocean Engineering》 2012年第1期10-17,共8页
This paper deals with time dependent performance characteristics of cavitating hydrofoils, the flow around which has been simulated using pressure-based finite volume method. A bubble dynamics cavitation model was use... This paper deals with time dependent performance characteristics of cavitating hydrofoils, the flow around which has been simulated using pressure-based finite volume method. A bubble dynamics cavitation model was used to investigate the unsteady behavior of cavitating flow and describe the generation and evaporation of vapor phase. For choosing the turbulence model and mesh size a non cavitating study was conducted. Three turbulence models such as Spalart-Allmaras, Shear Stress Turbulence (SST) κ-ω model, Re-Normalization Group (RNG) κ-ε model with enhanced wall treatment are used to capture the turbulent boundary layer along the hydrofoil surface. The cavitating study presents an unsteady behavior of the partial cavity attached to the foil at different time steps for σ = 0.8 and σ = 0.4. Moreover, this study is focused on cavitation inception, the shape and general behavior of sheet cavitation, lift and drag forces for different cavitation numbers. 展开更多
关键词 CAVITATION CAV2003 hydrofoil finite volume method turbulence model unsteady flow.
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Simulation of Hydrodynamic Performance of Drag and Double Reverse Propeller Podded Propulsors 被引量:6
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作者 Chunyu Guo Pengfei Dou +1 位作者 Tao Jing Dagang Zhao 《Journal of Marine Science and Application》 CSCD 2016年第1期16-27,共12页
The unsteady performance of drag and double reverse propeller podded propulsors in open water was numerically simulated using a computational fluid dynamics (CFD) method. A moving mesh method was used to more realis... The unsteady performance of drag and double reverse propeller podded propulsors in open water was numerically simulated using a computational fluid dynamics (CFD) method. A moving mesh method was used to more realistically simulate propulsor working conditions, and the thrust, torque, and lateral force coefficients of both propulsors were compared and analyzed. Forces acting on different parts of the propulsors along with the flow field distribution of steady and unsteady results at different advance coefficients were compared. Moreover, the change of the lateral force and the difference between the abovementioned two methods were mainly analyzed. It was shown that the thrust and torque results of both methods were similar, with the lateral force results having the highest deviation 展开更多
关键词 podded propulsor PROPELLER lateral force computational fluid dynamics (CFD) hydrodynamic performance moving mesh method
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