One-dimensional open channel flows are simulated using the discontinuous Galerkin finite element method. Three different explicit time marching schemes, including multistep/multistage schemes, are evaluated for differ...One-dimensional open channel flows are simulated using the discontinuous Galerkin finite element method. Three different explicit time marching schemes, including multistep/multistage schemes, are evaluated for different channel shapes for accuracy and efficiency. The Forward Euler, second-order Adam-Bashforth （multistep）, and second-order total variation diminishing （TVD） Runge-Kutta （multistage） time marching schemes are utilized. The role of monotonized central, minmod, and zero TVD slope limiters for each of the time marching scheme is investigated. The numerical flux is approximated using HLL function. The accuracy and robustness of different time marching schemes are evaluated for steady and unsteady flows using analytical and measured data. The unsteady flows include dam break tests with wet and dry beds downstream of the dam in prismatic （rectangular, trapezoidal, triangular, and parabolic cross-sections） and non-prismatic （natural river） channels. The steady flow test involves simulation of hydraulic jump in a diverging rectangular channel. The various schemes are evaluated by comparing accuracy using statistical measures and efficiency using maximum possible time step size as well as CPU runtime. The second-order Adam-Bashforth time marching scheme is found to have the best accuracy and efficiency among the time stepping schemes tested.展开更多
A time marching algorithms, which is used to solve incompressible internal flow fields in turbomachinery, has beendeveloped. By using Chorin’s method of artificial compressibility, the governing equations are transfo...A time marching algorithms, which is used to solve incompressible internal flow fields in turbomachinery, has beendeveloped. By using Chorin’s method of artificial compressibility, the governing equations are transformed fromelliptic type into hyperbolic form in order to extend the time marching technique to very low Mach number flows.Viscous effects can be predicted by using the distributed body force method and Baldwin-Lomax eddy viscosityturbulence model. Some accelerating convergence techniques such as multi-grid and local time step method areemployed. The applicahon to a flow field within a low-solidity rocket pump inducer is presented and discussed.展开更多
It’s a golden season of harvest during which it was a fine autumn weather with the pale clouds and a light breeze blowing in September in Beijing. The China International Economic and Trade Arbitration Commission and...It’s a golden season of harvest during which it was a fine autumn weather with the pale clouds and a light breeze blowing in September in Beijing. The China International Economic and Trade Arbitration Commission and China Maritime Arbitration Commission held a forum of arbitrators on 26 to 28 September 2001s dealing with arbitrate work in a beautiful landscape place, Kuan Gou, a suburb in Beijing. Mr. Yu Xiaosong, the Chair- man of China Council for Promotion of International Trade/China Chamber of International Commerce, China Intemational Economic and Trade Arbitration Commission and China Maritime Arbitration Commission, gave a talk at the forum stressed that the development of arbitration cause in China should be marched with ticccccccccmes and adapted to the fast development in the situations both of home and abroad. Mr. Yu Xaosong’s talk put forward a kind of principles for the development of the arbitration cause in China, a part of which, we publish part of it here as a reference for the arbitrate circle colleagues.展开更多
A throughflow model based on the time-marching finite volume approach is described in this paper. The governing equations are derived by circumferentially averaging the three-dimensional Navier-Stokes equations neglec...A throughflow model based on the time-marching finite volume approach is described in this paper. The governing equations are derived by circumferentially averaging the three-dimensional Navier-Stokes equations neglecting the circumferentially non-uniform and viscous terms. An inviscid blade force model similar to the Large-particle method is derived. The viscous blade force has been modeled by the distributed loss model. The convective fluxes of the governing equation are discretized with the Edward’s low-diffusion flux-splitting (LDFSS) scheme. And a point-iterative Symmetric Gauss-Seidel (SGS) scheme is used in the temporal discretization. The throughflow model has been applied to the NASA Rotor 67 and a high-load transonic fan stage ATS-2. The reasonable good agreements with the experiments and the 3D viscous computations show the potential of the method.展开更多
For the variable-density/viscosity Cahn-Hilliard phase-field model of the binary-phase incompressible fluid flow system, the development of easy-to-implement numerical schemes has long been known as a challenging prob...For the variable-density/viscosity Cahn-Hilliard phase-field model of the binary-phase incompressible fluid flow system, the development of easy-to-implement numerical schemes has long been known as a challenging problem. We develop a novel fully-decoupled numerical technique in this article which can achieve unconditional energy stability while explicitly discretizing nonlinear coupling items. The idea is invented on the basis of combining the Strang operator splitting method and the novel decoupling method by using the zero-energy-contribution property. The scheme only needs to solve a series of completely independent linear elliptic equations at each time step, in which the Cahn-Hilliard equation and the pressure Poisson equation are with constant coefficients. To demonstrate the effectiveness of the scheme, we provide the rigorous proof of the energy stability/solvability, and also perform ample accuracy and stability tests and 2D/3D numerical simulations, including the Rayleigh-Taylor instability and bubble rising dynamics.展开更多
A PLU-SGS method based on a time-derivative preconditioning algorithm and LU-SGS method is developed in order to calculate the Navier-Stokes equations at all speeds. The equations were discretized using A USMPW scheme...A PLU-SGS method based on a time-derivative preconditioning algorithm and LU-SGS method is developed in order to calculate the Navier-Stokes equations at all speeds. The equations were discretized using A USMPW scheme in conjunction with the third-order MUSCL scheme with Van Leer limiter. The present method was applied to solve the multidimensional compressible Navier-Stokes equations in curvilinear coordinates. Characteristic boundary conditions based on the eigensystem of the preconditioned equations were employed. In order to examine the performance of present method, driven-cavity flow at various Reynolds numbers and viscous flow through a convergent-divergent nozzle at supersonic were selected to rest this method. The computed results were compared with the experimental data or the other numerical results available in literature and good agreements between them are obtained. The results show that the present method is accurate, self-adaptive and stable for a wide range of flow conditions from low speed to supersonic flows.展开更多
Tow-phase flow mixed variational formulations of evolution filtration problems with seawater intrusion are analyzed. A dual mixed fractional flow velocity-pressure model is considered with an air-fresh water and a fre...Tow-phase flow mixed variational formulations of evolution filtration problems with seawater intrusion are analyzed. A dual mixed fractional flow velocity-pressure model is considered with an air-fresh water and a fresh water-seawater characterization. For analysis and computational purposes, spatial decompositions based on nonoverlapping multidomains, above and below the sea level, are variationally introduced with internal boundary fluxes dualized as weak transmission constraints. Further, parallel augmented and exactly penalized duality algorithms, and proximation semi-implicit time marching schemes, are established and analyzed.展开更多
Afast and accurate three dimensional (3 D) viscous code for calculating flows in turbomachinery has been established.In this code, H meshes are adopted to build the discrete equations, and the conservation equatio...Afast and accurate three dimensional (3 D) viscous code for calculating flows in turbomachinery has been established.In this code, H meshes are adopted to build the discrete equations, and the conservation equationsare solved on grid nodes atthe corners of cuboid elements.In orderto accelerate convergence,local time stepping,residualsmoothing and multigrid method are also applied,andthe viscous effects are approximatedby a very simple mixing length model.For verification ofthe accuracy and applicability ofthe method,transonicflowsthrough compressor cascades of NASArotor 37 and flows through a turbine stator of NASAhave been calculated.The good agreementbetween experimentalresults and design data has demonstratedthereliability and applicability ofthe present method,which can be usedforsimulatingthe complex 3 Dviscousflow phenomenonin turbomachinery.展开更多
文摘One-dimensional open channel flows are simulated using the discontinuous Galerkin finite element method. Three different explicit time marching schemes, including multistep/multistage schemes, are evaluated for different channel shapes for accuracy and efficiency. The Forward Euler, second-order Adam-Bashforth （multistep）, and second-order total variation diminishing （TVD） Runge-Kutta （multistage） time marching schemes are utilized. The role of monotonized central, minmod, and zero TVD slope limiters for each of the time marching scheme is investigated. The numerical flux is approximated using HLL function. The accuracy and robustness of different time marching schemes are evaluated for steady and unsteady flows using analytical and measured data. The unsteady flows include dam break tests with wet and dry beds downstream of the dam in prismatic （rectangular, trapezoidal, triangular, and parabolic cross-sections） and non-prismatic （natural river） channels. The steady flow test involves simulation of hydraulic jump in a diverging rectangular channel. The various schemes are evaluated by comparing accuracy using statistical measures and efficiency using maximum possible time step size as well as CPU runtime. The second-order Adam-Bashforth time marching scheme is found to have the best accuracy and efficiency among the time stepping schemes tested.
文摘A time marching algorithms, which is used to solve incompressible internal flow fields in turbomachinery, has beendeveloped. By using Chorin’s method of artificial compressibility, the governing equations are transformed fromelliptic type into hyperbolic form in order to extend the time marching technique to very low Mach number flows.Viscous effects can be predicted by using the distributed body force method and Baldwin-Lomax eddy viscosityturbulence model. Some accelerating convergence techniques such as multi-grid and local time step method areemployed. The applicahon to a flow field within a low-solidity rocket pump inducer is presented and discussed.
文摘It’s a golden season of harvest during which it was a fine autumn weather with the pale clouds and a light breeze blowing in September in Beijing. The China International Economic and Trade Arbitration Commission and China Maritime Arbitration Commission held a forum of arbitrators on 26 to 28 September 2001s dealing with arbitrate work in a beautiful landscape place, Kuan Gou, a suburb in Beijing. Mr. Yu Xiaosong, the Chair- man of China Council for Promotion of International Trade/China Chamber of International Commerce, China Intemational Economic and Trade Arbitration Commission and China Maritime Arbitration Commission, gave a talk at the forum stressed that the development of arbitration cause in China should be marched with ticccccccccmes and adapted to the fast development in the situations both of home and abroad. Mr. Yu Xaosong’s talk put forward a kind of principles for the development of the arbitration cause in China, a part of which, we publish part of it here as a reference for the arbitrate circle colleagues.
基金supported by National Natural Science Foundation of China (50676004, 50736007)"Fan-Zhou" Youth Foundation (20100401)the Fun-damental Research Funds for the Central Universities (YWF-10-02-013)
文摘A throughflow model based on the time-marching finite volume approach is described in this paper. The governing equations are derived by circumferentially averaging the three-dimensional Navier-Stokes equations neglecting the circumferentially non-uniform and viscous terms. An inviscid blade force model similar to the Large-particle method is derived. The viscous blade force has been modeled by the distributed loss model. The convective fluxes of the governing equation are discretized with the Edward’s low-diffusion flux-splitting (LDFSS) scheme. And a point-iterative Symmetric Gauss-Seidel (SGS) scheme is used in the temporal discretization. The throughflow model has been applied to the NASA Rotor 67 and a high-load transonic fan stage ATS-2. The reasonable good agreements with the experiments and the 3D viscous computations show the potential of the method.
基金supported by National Natural Science Foundation of China(Grant No.11771375)supported by National Science Foundation of USA(Grant No.DMS2012490)。
文摘For the variable-density/viscosity Cahn-Hilliard phase-field model of the binary-phase incompressible fluid flow system, the development of easy-to-implement numerical schemes has long been known as a challenging problem. We develop a novel fully-decoupled numerical technique in this article which can achieve unconditional energy stability while explicitly discretizing nonlinear coupling items. The idea is invented on the basis of combining the Strang operator splitting method and the novel decoupling method by using the zero-energy-contribution property. The scheme only needs to solve a series of completely independent linear elliptic equations at each time step, in which the Cahn-Hilliard equation and the pressure Poisson equation are with constant coefficients. To demonstrate the effectiveness of the scheme, we provide the rigorous proof of the energy stability/solvability, and also perform ample accuracy and stability tests and 2D/3D numerical simulations, including the Rayleigh-Taylor instability and bubble rising dynamics.
文摘A PLU-SGS method based on a time-derivative preconditioning algorithm and LU-SGS method is developed in order to calculate the Navier-Stokes equations at all speeds. The equations were discretized using A USMPW scheme in conjunction with the third-order MUSCL scheme with Van Leer limiter. The present method was applied to solve the multidimensional compressible Navier-Stokes equations in curvilinear coordinates. Characteristic boundary conditions based on the eigensystem of the preconditioned equations were employed. In order to examine the performance of present method, driven-cavity flow at various Reynolds numbers and viscous flow through a convergent-divergent nozzle at supersonic were selected to rest this method. The computed results were compared with the experimental data or the other numerical results available in literature and good agreements between them are obtained. The results show that the present method is accurate, self-adaptive and stable for a wide range of flow conditions from low speed to supersonic flows.
文摘Tow-phase flow mixed variational formulations of evolution filtration problems with seawater intrusion are analyzed. A dual mixed fractional flow velocity-pressure model is considered with an air-fresh water and a fresh water-seawater characterization. For analysis and computational purposes, spatial decompositions based on nonoverlapping multidomains, above and below the sea level, are variationally introduced with internal boundary fluxes dualized as weak transmission constraints. Further, parallel augmented and exactly penalized duality algorithms, and proximation semi-implicit time marching schemes, are established and analyzed.
文摘Afast and accurate three dimensional (3 D) viscous code for calculating flows in turbomachinery has been established.In this code, H meshes are adopted to build the discrete equations, and the conservation equationsare solved on grid nodes atthe corners of cuboid elements.In orderto accelerate convergence,local time stepping,residualsmoothing and multigrid method are also applied,andthe viscous effects are approximatedby a very simple mixing length model.For verification ofthe accuracy and applicability ofthe method,transonicflowsthrough compressor cascades of NASArotor 37 and flows through a turbine stator of NASAhave been calculated.The good agreementbetween experimentalresults and design data has demonstratedthereliability and applicability ofthe present method,which can be usedforsimulatingthe complex 3 Dviscousflow phenomenonin turbomachinery.
