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Unsteady Numerical Simulation of Flow around 2-D Circular Cylinder for High Reynolds Numbers 被引量:7
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作者 Yanhui Ai Dakui Feng +1 位作者 Hengkui Ye Lin Li 《Journal of Marine Science and Application》 2013年第2期180-184,共5页
In this paper, 2-D computational analyses were conducted for unsteady high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. 8.21×104〈Re〈1.54&#... In this paper, 2-D computational analyses were conducted for unsteady high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. 8.21×104〈Re〈1.54×106. The calculations were performed by means of solving the 2-D Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with a k-ε turbulence model. The calculated results, produced flow structure drag and lift coefficients, as well as Strouhal numbers. The findings were in good agreement with previous published data, which also supplied us with a good understanding of the flow across cylinders of different high Reynolds numbers. Meanwhile, an effective measure was presented to control the lift force on a cylinder, which points the way to decrease the vortex induced vibration of marine structure in future. 展开更多
关键词 circular cylinder vortex shedding high Reynolds number Strouhal numbers lift control measure marine structure unsteady numerical simulation
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A numerical simulation of unsteady flow in small diameter helical grafts
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作者 Tinghui Zheng2,Yubo Fan1,Weizhong Wang2,Wentao Jiang2,Xiaoyan Deng1(1.School of Biological Science and Medical Engineering,Beihang University,Beijing,China 2.Department of Applied Mechanics,Sichuan University,Chengdu,Chin 《医用生物力学》 EI CAS CSCD 2009年第S1期40-41,共2页
The application of small diameter arterial grafts is limited due to the fact of relatively poor long-time patency which is caused by thrombosis formation in the short term and intimal hyperplasia(IH) in the medium and... The application of small diameter arterial grafts is limited due to the fact of relatively poor long-time patency which is caused by thrombosis formation in the short term and intimal hyperplasia(IH) in the medium and long term.Thrombosis,obstructing the flow of blood 展开更多
关键词 A numerical simulation of unsteady flow in small diameter helical grafts FLOW
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NUMERICAL SIMULATION OF UNSTEADY FLOW AROUND A CIRCULAR CYLINDER AT HIGH REYNOLDS NUMBERS
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作者 Yin Xieyuan Tong Bingang University of Science and Technology of ChinaHefei, Anhui, 230026, ChinaTao Feng Institute of Mechanics, Acadmia Sinica,Beijing, 100080, China 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 1991年第2期198-206,共9页
A Lagrangian-Eulerian hybrid scheme to solve unsteady N-S equation in two-dimensional incompressible fluid at high Reynolds numbers is presented in this paper. A random walk is imposed to simulate the viscous diffusio... A Lagrangian-Eulerian hybrid scheme to solve unsteady N-S equation in two-dimensional incompressible fluid at high Reynolds numbers is presented in this paper. A random walk is imposed to simulate the viscous diffusion, the vortex-in-cell method is used to obtain the convection velocity, and nascent vortices are created on a cylinder to satisfy the zero-slip condition. The impulsively started flow around a circular cylinder and the separation induced by a pair of incident vortices symmetrically approaching a circular cylinder have been successfully simulated by the hybrid scheme. The impulsively started flow from rest has been computed at Reynolds numbers 3000 and 9500. Comparisons are made with those results of finite-difference method, vortex method and flow visualization. Agreement is good. The particular attention has been paid to the evolutions of flow pattern. A topological analysis has been proposed in the region of the near wake. The bulge, isolated secondary vortex, a pair of secondary vortices, ' forewake phenomenon and other patterns are simulated numerically. The separation induced by a pair of incident vortices approaching a circular cylinder has been investigated by using the same scheme. The rebounding phenomenon of the incident vortex is observed and is attributed to the effect of the secondary vortex. In particular, we have found that a tertiary vortex can be formed near the surface; this phenomenon has been verified by flow visualization reported recently. 展开更多
关键词 NUMERICAL simulation OF unsteady FLOW AROUND A CIRCULAR CYLINDER AT HIGH REYNOLDS NUMBERS AT
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Numerical Simulation of Wake Deflection Control around NACA0012 Airfoil Using Active Morphing Flaps
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作者 Yoshiaki Abe Takayuki Konishi Tomonaga Okabe 《Journal of Flow Control, Measurement & Visualization》 2020年第3期121-133,共13页
This study demonstrates an active flow control for deflecting a direction of wake vortex structures behind a NACA0012 airfoil using an active morphing flap. Two-dimensional direct numerical simulations are performed f... This study demonstrates an active flow control for deflecting a direction of wake vortex structures behind a NACA0012 airfoil using an active morphing flap. Two-dimensional direct numerical simulations are performed for flows at the chord Reynolds number of 10,000, and the vortex pattern in the controlled and noncontrolled wakes as well as the effect of an actuation frequency on the control ability are rigorously investigated. It is found that there is an optimum actuation-frequency regime at around <em>F <sup>+</sup></em> = 2.00 which is normalized by the chord length and freestream velocity. The wake vortex pattern of the well-controlled case is classified as the 2P wake pattern according to the Williamson’s categorization [<a href="#ref1">1</a>] [<a href="#ref2">2</a>], where the forced oscillation frequency corresponds to the natural vortex shedding frequency without control. The present classification of wake vortex patterns and finding of the optimum frequency regime in the wake deflection control can lead to a more robust design suitable for vortex-induced-vibration (VIV) related engineering systems. 展开更多
关键词 Flow Control Wake Deflection Control VORTEX Morphing Flap Direct Numerical simulation unsteady Flow simulation
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Study of Unsteady Flow Simulation of Backward Impeller with Non-uniform Casing 被引量:2
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作者 War War Min Swe Hiroya MORIMATSU +2 位作者 Hidechito HAYASHI Tetsuya OKUMURA Ippei ODA 《Journal of Thermal Science》 SCIE EI CAS CSCD 2017年第3期208-213,共6页
The flow characteristics of the centrifugal fans with different blade outlet angles are basically discussed on steady and unsteady simulations for a rectangular casing fan. The blade outlet angles of the impellers are... The flow characteristics of the centrifugal fans with different blade outlet angles are basically discussed on steady and unsteady simulations for a rectangular casing fan. The blade outlet angles of the impellers are 35° and 25° respectively. The unsteady flow behavior in the passage of the impeller 35° is quite different from that in the steady flow behavior. The large flow separation occurs in the steady flow field and unsteady flow field of the impeller 35°, the flow distribution in the circumferential direction varies remarkably and the flow separation on the blade occurs only at the back region of the fan; but the steady flow behavior in the impeller 25° is almost consistent with the unsteady flow behavior, the flow distribution of the circumferential direction doesn't vary much and the flow separation on the blade hardly occurs. When the circumferential variation of the flow in the impeller is large, the steady flow simulation is not coincident to the unsteady flow simulation. 展开更多
关键词 Centrifugal fan IMPELLER Blade outlet angles Steady and unsteady simulation Rectangular casing
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Development of a Balanced Adaptive Time‑Stepping Strategy Based on an Implicit JFNK‑DG Compressible Flow Solver
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作者 Yu Pan Zhen‑Guo Yan +1 位作者 Joaquim Peiró Spencer J.Sherwin 《Communications on Applied Mathematics and Computation》 2022年第2期728-757,共30页
A balanced adaptive time-stepping strategy is implemented in an implicit discontinuous Galerkin solver to guarantee the temporal accuracy of unsteady simulations.A proper relation between the spatial,temporal and iter... A balanced adaptive time-stepping strategy is implemented in an implicit discontinuous Galerkin solver to guarantee the temporal accuracy of unsteady simulations.A proper relation between the spatial,temporal and iterative errors generated within one time step is constructed.With an estimate of temporal and spatial error using an embedded RungeKutta scheme and a higher order spatial discretization,an adaptive time-stepping strategy is proposed based on the idea that the time step should be the maximum without obviously infuencing the total error of the discretization.The designed adaptive time-stepping strategy is then tested in various types of problems including isentropic vortex convection,steady-state fow past a fat plate,Taylor-Green vortex and turbulent fow over a circular cylinder at Re=3900.The results indicate that the adaptive time-stepping strategy can maintain that the discretization error is dominated by the spatial error and relatively high efciency is obtained for unsteady and steady,well-resolved and under-resolved simulations. 展开更多
关键词 Adaptive time-stepping unsteady simulations High order Discontinuous Galerkin Implicit time integration
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Unsteady Numerical Simulation of Steam-Solid Two-Phase Flow in the Governing Stage of a Steam Turbine 被引量:2
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作者 Yufeng Li Peigang Yan Wanjin Han 《Journal of Thermal Science》 SCIE EI CAS CSCD 2009年第4期313-320,共8页
Solid particle erosion (SPE) in an ultra-supercritical steam turbine control stage with block configuration is investigatednumerically, based on the finite volume method and the fluid-particle coupling solver. We appl... Solid particle erosion (SPE) in an ultra-supercritical steam turbine control stage with block configuration is investigatednumerically, based on the finite volume method and the fluid-particle coupling solver. We apply the particlediscrete phase model to model the solid particles flow, and use the Euler conservation equations to solve thecontinuous phase. The investigation is focused on the influence of the solid particle parameters (such as particlediameter, particle velocity and particle trajectory) on the erosion rate of the stator and rotor blade surface in unsteadycondition. The distributions of the highly eroded zone on the stator and rotor blade surfaces are shown anddiscussed in detail according to the mechanism of solid particle/blade wall interaction. We obtain that the erosionrate of the vane blade is sensitive to the fluctuation of the potential flow field, and the smaller particle has agreater impact on the erosion distribution of rotor blade. The erosion rate does not entirely depend on the diametersize of the solid particle. 展开更多
关键词 steam turbine unsteady numerical simulation solid particle EROSION BLADE
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A NEW APPROACH TO THE SIMULATION OF UNSTEADY SUBCRITICAL FLOW 被引量:2
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作者 Mao Ze-yu(Department of Hydraulic Engineering, Tsinghua University Beijing 100084, P. R. China) 《Journal of Hydrodynamics》 SCIE EI CSCD 1995年第3期84-93,共10页
The use of the specified time interval numerical schemes has been popular in applying the method of characteristics to unsteady oped-channel flow problem. Studies and analyses of several variants of those schemes have... The use of the specified time interval numerical schemes has been popular in applying the method of characteristics to unsteady oped-channel flow problem. Studies and analyses of several variants of those schemes have led to the derivation of a complete set of timeline-interpolation scheme in applying the method of characteristics to Saint-Venant equations. A computer model based upon this scheme has ben successfully developed for predicting free surface unsteady flow, and has been verified by field experiment. Timeline interpolations, where the characteristic lines are projected back before the current time step,demonstrate much less damping than the corresponding spatial interpolation scheme at the same discretization. 展开更多
关键词 open-channel flow unsteady flow simulation characteristics method timeline interpolation scheme
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Unsteady numerical simulation on helium cooldown process for the 650 MHz two-cell superconducting cavity
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作者 Mei Li Zhengze Chang +1 位作者 Shaopeng Li Rui Ge 《Radiation Detection Technology and Methods》 CSCD 2019年第4期18-28,共11页
Background Superconducting cavity is usually needed to be gradually cooled from room temperature to the superconducting temperature zone(4.2 K and below)in the testing and sophisticated operation process of supercondu... Background Superconducting cavity is usually needed to be gradually cooled from room temperature to the superconducting temperature zone(4.2 K and below)in the testing and sophisticated operation process of superconducting cavity.Purpose The purpose of this paper is to study the cooling law on the helium cooldown process for the 650 MHz two-cell superconducting cavity with the unsteady numerical simulation.Method A three-dimensional coupled heat-flow model of 650 MHz two-cell superconducting cavity was established.The unsteady numerical simulation of different inlet temperatures,flow rates and pressure conditions was carried out.The equiva-lent convective heat transfer coefficient and temperature distribution of 650 MHz two-cell superconducting cavity during cooldown process were obtained.The effects of cooling time and entrance parameters on the cooldown process were analyzed.Results The temperature distribution of the lower intersection lines has a large drop in the initial stage of cooldown process(120 s),while the temperature near the flanges at the both ends is still higher(remaining at the initial temperature of 300 K).With the passage of time,the temperature of the upper and lower intersection lines decreases.The maximum temperature difference on the lower intersections is within 2 K in the final stage of cooldown process(3600 s).The maximum temperature difference increases by 180%,and the difference between the maximum temperature and the minimum temperature(dT)at the end of a cooldown stage increases by 130%after 1 h,respectively,when the inlet temperature drops from 290 to 270 K(under the condition of the initial temperature of 300 K).Conclusions The maximum temperature difference and the dT at the end of a cooldown stage increase with the decrease in the inlet temperature.The maximum temperature difference increases with the increase in the inlet flow rate,while the dT at the end of a cooldown stage decreases with the increase in the inlet flow rate.The effect of changing the inlet flow rate on the cooling rate is not as obvious as changing the inlet temperature.Once there is a certain flow rate,the advantage of further increasing the flow rate to reduce the temperature of the superconducting cavity is not so great. 展开更多
关键词 ACCELERATOR Superconducting cavity Helium gas Cooldown process unsteady numerical simulation
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The effects of the rotor-stator interaction on unsteady pressure pulsation and radial force in a centrifugal pump 被引量:13
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作者 Issa Chalghoum Sami Elaoud +1 位作者 Hatem Kanfoudi Mohsen Akrout 《Journal of Hydrodynamics》 SCIE EI CSCD 2018年第4期672-681,共10页
An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport tur... An unsteady numerical analysis has been conducted to study the strong interaction between impeller blade and volute tongue of a centrifugal pump. The 3-D-URANS equations were solved with the shear stress transport turbulence model for a wide range of flow rates. These unsteady interactions are mostly related to the unsteady radial force due to an imbalance in the pressure field at the impeller periphery. This force represents dynamic load that are one of the most important sources of vibration and hydraulic noise. Based on this phenomenon, this work analyzes and gives a more realistic prediction of the pressure fluctuation and the radial force during steady and unsteady calculation by considering the effect of the change in the pump operating point. Actually, the pressure fluctuations in the impeller and the volute were recorded by mounting nine monitoring points on the impeller and volute casing. The results of the existing analysis has proven that the pressure fluctuation is periodic due to the relative position of impeller blade to volute tongue. The characteristics of the time domain and frequency domain of the pressure pulsation were analyzed under different coupling conditions. Fast Fourier transform was performed to obtain the spectra of pressure pulsation. Besides, the steady and unsteady forces were calculated around the impeller periphery to fully characterize the pump behavior. The obtained pump performance curves were numerically compared with the experimental ones, and the outcome have shown an acceptable agreement between both curves. 展开更多
关键词 unsteady simulation blade-tongue interaction unsteady pressure distribution blade-passing frequency
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Unsteady Study on the Effects of Matching Characteristic of Tandem Cascade on the Performance and Flow at Large Angle of Attack 被引量:7
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作者 LIU Hanru YUE Shaoyuan +1 位作者 WANG Yangang ZHANG Jun 《Journal of Thermal Science》 SCIE EI CAS CSCD 2018年第6期505-515,共11页
To investigate the effects of matching characteristics of tandem cascade on the performance and flow at large angle of attack, the unsteady numerical simulation has been implemented. The influences of different turnin... To investigate the effects of matching characteristics of tandem cascade on the performance and flow at large angle of attack, the unsteady numerical simulation has been implemented. The influences of different turning angle ratio(TR) and chord length ratio(CR) of two blades and the relative angle of attack of rear blade(Delta) are analyzed. The numerical results indicated that the tandem cascade can obtain overall performance improvement including higher static pressure ratio and lower total pressure loss with the matching parameters in the range of TR=3~5, CR=0.5~1.2, and Delta=-15°~-5°. The separation on the front blade has more prominent impact than that on the rear blade, so the performance improvement of tandem cascade is significantly dependent on the reduction of front-blade separation and loss. Regarding the rear blade, the gap injection effect can periodically control the separation. Temporal and spatial analysis of the flow field shows that the optimal-performance cases generally have much smaller wake loss for both two blades, but the unsteady characteristics of the wake loss is more apparent than that of the poor performance cases. 展开更多
关键词 tandem cascade unsteady simulation matching parameters aerodynamics performance flow loss
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Numerical Investigations of the Influence of Unsteady Vane Trailing Edge Shock Wave on Film Cooling Effectiveness of Rotor Blade Leading Edge 被引量:3
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作者 WANG Yufeng CAI Le +1 位作者 WANG Songtao ZHOU Xun 《Journal of Thermal Science》 SCIE EI CAS CSCD 2018年第2期135-145,共11页
Unsteady numerical simulations of a high-load transonic turbine stage have been carried out to study the influences of vane trailing edge outer-extending shockwave on rotor blade leading edge film cooling performance.... Unsteady numerical simulations of a high-load transonic turbine stage have been carried out to study the influences of vane trailing edge outer-extending shockwave on rotor blade leading edge film cooling performance. The turbine stage used in this paper is composed of a vane section and a rotor one which are both near the root section of a transonic high-load turbine stage. The Mach number is 0.94 at vane outlet, and the relative Mach number is above 1.10 at rotor outlet. Various positions and oblique angles of film cooling holes were investigated in this research. Results show that the cooling efficiency on the blade surface of rotor near leading edge is significantly affected by vane trailing edge outer-extending shockwave in some cases. In the cases that film holes are close to leading edge, cooling performance suffers more from the sweeping vane trailing edge outer-extending shockwave.In addition, coolant flow ejected from oblique film holes is harder to separate from the blade surface of rotor, and can cover more blade area even under the effects of sweeping vane trailing edge shockwave. As a result, oblique film holes can provide better film cooling performance than vertical film holes do near the leading edge on turbine blade which is swept by shockwaves. 展开更多
关键词 transonic turbine trailing edge shock wave ftlm cooling unsteady simulation
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Influence of Reynolds Number on the Unsteady Aerodynamics of Integrated Aggressive Intermediate Turbine Duct 被引量:1
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作者 LIU Hongrui LIU Jun +3 位作者 JI Lucheng DU Qiang LIU Guang WANG Pei 《Journal of Thermal Science》 SCIE EI CAS CSCD 2018年第3期294-303,共10页
The ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine due to advantages of high efficiency and low Specific Fuel Consumption(SFC). One of the characteristics of ultra... The ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine due to advantages of high efficiency and low Specific Fuel Consumption(SFC). One of the characteristics of ultra-high bypass ratio turbofan is the intermediate turbine duct which guides the flow leaving high pressure turbine(HPT) to low pressure turbine(LPT) at a larger diameter, and this kind of design will lead to aggressive intermediate turbine duct(AITD) design concept. Thus, it is important to design the AITD without any severe loss. From the unsteady flow's point of view, in actual operating conditions, the incoming wake generated by HPT is unsteady which will take influence on boundary layer's transition within the ITD and LPT. In this paper, the three-dimensional unsteady aerodynamics of an AITD taken from a real engine is studied. The results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX(RANS simulation with transitional model), are critically evaluated against experimental data. After validation of the numerical model, the physical mechanisms inside the flow channel are analyzed, with an aim to quantify the sensitivities of different Reynolds number effect on both the ITD and LPT nozzle. Some general physical mechanisms can be recognized in the unsteady environment. It is recognized that wake characteristics plays a crucial role on the loss within both the ITD and LPT nozzle section, determining both time-averaged and time-resolved characteristics of the flow field. Meanwhile, particular attention needs to be paid to the unsteady effect on the boundary layer of LPT nozzle's suction side surface. 展开更多
关键词 Intermediate Turbine Duct unsteady simulation Reynolds Number Flow Field Analysis
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Time-delay effect and design of closed-loop control system of circulation control airfoil
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作者 Lingxiao Li Heyong XU +1 位作者 Zheng XING Abdul Samad KHAN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2024年第10期50-67,共18页
In this paper,unsteady numerical simulation of jet Circulation Control(CC)is carried out with the NACA0012-CC airfoil as the research object.The dynamic process from the opening of jet slot and adjustment of jet inten... In this paper,unsteady numerical simulation of jet Circulation Control(CC)is carried out with the NACA0012-CC airfoil as the research object.The dynamic process from the opening of jet slot and adjustment of jet intensity to the stable state of jet control effect is explored.The time-delay effect and flow mechanism of jet are analyzed.The mechanism of jet momentum coefficient and moment coefficient fluctuating with time is revealed.The fluctuation of jet momentum coefficient is caused by the change of the pressure coefficient distribution on the Coanda surface or the structure of the wave system inside the jet,and the oscillation frequency of the wave system structure of the under-expansion supersonic jet reaches 1481 Hz at the opening moment.Based on the aerodynamic model and Proportional-Integral-Derivative(PID)control theory,the closed-loop control system of CC airfoil is designed.The parameters of PID control system are adjusted by the Genetic Algorithm(GA),which significantly improves the response ability of the control system to step,ramp and sine signals,and improves the dynamic performance of the system.Aimed at the special time-delay effect of jet control,Long Short-Term Memory(LSTM)neural network module is added to the control system to predict the target input signal,which strengthens the prediction ability of GA-PID control system to the target signal at the next time moment.By using LSTM neural network correction,the control hysteresis caused by jet time-delay effect is alleviated,and the response ability of the control system is effectively improved.Finally,the designed LSTM-GA-PID control system is applied to the NACA0012-CC airfoil for the pitch control simulation test.The test results show that the control system designed in this paper has good dynamic performance and can respond quickly and accurately to complex input signals,which confirms the effectiveness of the control system. 展开更多
关键词 Circulation control unsteady numerical simulation Time-delay effect Control system Long short-term memory
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NUMERICAL SIMULATION OF HIGH TURBULENT FREE SURFACE FLOW UNDER THE CURVILINEAR COORDINATES
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作者 Xu Wei-xin, Jin Zhong-qingWater Power Department of Hohai University, Nanjing 210098. P. R. ChinaWang Da-yunHarbin Engineering University, Harbin 150001, P. R.China 《Journal of Hydrodynamics》 SCIE EI CSCD 1997年第3期1-8,共8页
This paper presents a new numerical method to simulate the high velocity turbulent flow with free surface by solving two-dimensional incompressible unsteady Navier-Stokes Eqs. , together with the k-ε turbulence model... This paper presents a new numerical method to simulate the high velocity turbulent flow with free surface by solving two-dimensional incompressible unsteady Navier-Stokes Eqs. , together with the k-ε turbulence model. In order to treat the non-rectangular boundary (or curvilinear boundary), orthogonal boundary-fitted grid is used and the Navier-Stokes Eqs. and k-ε turbulence model are rewritten and discreted in orthogonal curvilinear coordinates. Meanwhile, gas-liquid two-field model theory is introduced to treat the free-surface problem. 展开更多
关键词 k-εturbulence model curvilinear coordinates unsteady simulation nonlinear free surface motion
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Numerical simulation of pressure fluctuation in Kaplan turbine 被引量:9
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作者 LIU ShuHong SHAO Jie +1 位作者 WU ShangFeng WU YuLin 《Science China(Technological Sciences)》 SCIE EI CAS 2008年第8期1137-1148,共12页
As it is almost impossible to carry out the prototype hydro-turbine experiment be- fore the power plant is built up, rational prediction of pressure fluctuations in the prototype turbine is very important at the desig... As it is almost impossible to carry out the prototype hydro-turbine experiment be- fore the power plant is built up, rational prediction of pressure fluctuations in the prototype turbine is very important at the design stage. From this viewpoint, we at first treated the unsteady turbulent flow computation based on the modified RNG k-ε turbulence model through the whole flow passage to simulate the pressure fluctuation in a model turbine. Since fair agreement was recognized between the numerical results and the experimental data, this numerical method was applied to simulate the pressure fluctuations in the prototype turbine. From the comparison of them with the model turbine results, it is seen that their qualitative trend of pres- sure fluctuations are similar, but an appreciable difference is observed between the amplitudes of pressure fluctuation of the prototype turbine and that of the model turbine. Though the present findings may be explained by the effect of Reynolds number, further studies are expected for quantitative interpretation. We paid atten- tion to the interaction between the fluid and turbine structure. Adopting a weak fluid-solid coupling method, we studied the pressure fluctuation in the prototype turbine to clarify how the elastic behavior of runner blades influenced the charac- teristics of pressure fluctuation. 展开更多
关键词 RNG k-ε turbulence model Kaplan turbine pressure fluctuation unsteady flow simulation
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Numerical Simulation for Effect of Inlet Cooling Rate on Fluid Flow and Temperature Distribution in Tundish 被引量:7
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作者 QU Tian-peng LIU Cheng-jun JIANG Mao-fa 《Journal of Iron and Steel Research International》 SCIE CAS CSCD 2012年第7期12-19,共8页
The fluid flow in tundish is a non-isothermal process and the temperature variation of stream from teeming ladle dominates the fluid flow and thermal distribution in tundish. A numerical model was established to inves... The fluid flow in tundish is a non-isothermal process and the temperature variation of stream from teeming ladle dominates the fluid flow and thermal distribution in tundish. A numerical model was established to investigate the effect of inlet cooling rate on fluid flow and temperature distribution in tundish based on a FTSC (Flexible Thin Slab Casting) tundish. The inlet cooling rate varies from 0. 5 to 0. 25 ~C/rain. Under the present calculation conditions, the following conclusions were made. When the stream temperature from teeming ladle drops seriously (for inlet cooling rate of 0.5℃/min), there is a "backward flow" at the coming end of casting. The horizontal flow along the free surface turns to flow along the bottom of tundish. The bottom flow shortens the fluid flow route in tundish and deteriorates the removal effect of nonmetallic inclusions from molten steel. Nevertheless, when the inlet cooling rate decreases to 0.25℃/min, the horizontal flow is sustained during the whole casting period. The present research provides theoretical directions for temperature control in teeming ladle and continuous casting tundish during production of advanced steels. 展开更多
关键词 TUNDISH thermal distribution unsteady numerical simulation
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Unsteady flow characteristic analysis of turbine based combined cycle(TBCC)inlet mode transition10.1016/j.jppr.2015.07.006 被引量:5
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作者 Jun Liu Huacheng Yuan Rongwei Guo 《Propulsion and Power Research》 SCIE 2015年第3期141-149,共9页
A turbine based combined cycle(TBCC)propulsion system uses a turbine-based engine to accelerate the vehicle from takeoff to the mode transition flight condition,at which point,the propulsion system performs a“mode tr... A turbine based combined cycle(TBCC)propulsion system uses a turbine-based engine to accelerate the vehicle from takeoff to the mode transition flight condition,at which point,the propulsion system performs a“mode transition”from the turbine to ramjet engine.Smooth inlet mode transition is accomplished when flow is diverted from one flowpath to the other,without experiencing unstart or buzz.The smooth inlet mode transition is a complex unsteady process and it is one of the enabling technologies for combined cycle engine to become a functional reality.In order to unveil the unsteady process of inlet mode transition,the research of over/under TBCC inlet mode transition was conducted through a numerical simulation.It shows that during the mode transition the terminal shock oscillates in the inlet.During the process of inlet mode transition mass flow rate and Mach number of turbojet flowpath reduce with oscillation.While in ramjet flowpath the flow field is non-uniform at the beginning of inlet mode transition.The speed of mode transition and the operation states of the turbojet and ramjet engines will affect the motion of terminal shock.The result obtained in present paper can help us realize the unsteady flow characteristic during the mode transition and provide some suggestions for TBCC inlet mode transition based on the smooth transition of thrust. 展开更多
关键词 Airbreathing hypersonic vehicle Turbine based combined cycle(TBCC) Inlet mode transition unsteady numerical simulation Shock oscillation
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Large-eddy simulation: Past, present and the future 被引量:20
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作者 Yang Zhiyin 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2015年第1期11-24,共14页
Large-eddy simulation(LES) was originally proposed for simulating atmospheric flows in the 1960 s and has become one of the most promising and successful methodology for simulating turbulent flows with the improveme... Large-eddy simulation(LES) was originally proposed for simulating atmospheric flows in the 1960 s and has become one of the most promising and successful methodology for simulating turbulent flows with the improvement of computing power. It is now feasible to simulate complex engineering flows using LES. However, apart from the computing power, significant challenges still remain for LES to reach a level of maturity that brings this approach to the mainstream of engineering and industrial computations. This paper will describe briefly LES formalism first, present a quick glance at its history, review its current state focusing mainly on its applications in transitional flows and gas turbine combustor flows, discuss some major modelling and numerical challenges/issues that we are facing now and in the near future, and finish with the concluding remarks. 展开更多
关键词 turbulent turbulence simulating Reynolds transitional mainstream briefly maturity focusing unsteady
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Unsteady Flow Variability Driven by Rotor-stator Interaction at Rotor Exit 被引量:5
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作者 ZHAO Ben YANG Ce +2 位作者 CHEN Shan QI Mingxu ZHOU Mi 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2012年第6期871-878,共8页
Numerical investigation of the unsteady flow variability driven by rotorstator interaction in a transonic axial compressor is performed. Two models with close and far axial gap between rotor and stator rows are studie... Numerical investigation of the unsteady flow variability driven by rotorstator interaction in a transonic axial compressor is performed. Two models with close and far axial gap between rotor and stator rows are studied in the simulation. Particular attention is attached to the analysis of mechanisms involved in driving rotor wake oscillation, rotor wake skewing and flow angle fluctuation at rotor exit. The results show that smaller axial gap is favorable to enhance the interaction in the region between two adjacent rows, and the fluctuation of the static pressure difference between two sides of rotor wake is improved by potential field from down stator, which is the driving force for rotor wake oscillation. The interaction between rotor and stator is weakened by increasing axial distance, rotor wake shifts to suction side of rotor blade with 5%-10% of rotor pitch, the absolute value of flow angle at rotor exit is less than that in the case of close interspace for every time step, and the fluctuation amplitude is also decreased. 展开更多
关键词 transonic compressor numerical simulation rotor-stator interaction unsteady flow wake oscillation
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