A cell centered scheme for three dimensional Navier Stokes equations, which is based on central difference approximations and Runge Kutta time stepping, is described. By using local time stepping, implicit residual sm...A cell centered scheme for three dimensional Navier Stokes equations, which is based on central difference approximations and Runge Kutta time stepping, is described. By using local time stepping, implicit residual smoothing, a multigrid method, and carefully controlled artificial dissipative terms, good convergence rates are obtained for two and three dimensional flows. The emphases are on the implicit smoothing and artificial dissipative terms with locally variable coefficients which depend on cel...展开更多
In order to solve unsteady incompressible Navier–Stokes(N–S) equations, a new stabilized finite element method,called the viscous-splitting least square FEM, is proposed. In the model, the N–S equations are split i...In order to solve unsteady incompressible Navier–Stokes(N–S) equations, a new stabilized finite element method,called the viscous-splitting least square FEM, is proposed. In the model, the N–S equations are split into diffusive and convective parts in each time step. The diffusive part is discretized by the backward difference method in time and discretized by the standard Galerkin method in space. The convective part is a first-order nonlinear equation.After the linearization of the nonlinear part by Newton’s method, the convective part is also discretized by the backward difference method in time and discretized by least square scheme in space. C0-type element can be used for interpolation of the velocity and pressure in the present model. Driven cavity flow and flow past a circular cylinder are conducted to validate the present model. Numerical results agree with previous numerical results, and the model has high accuracy and can be used to simulate problems with complex geometry.展开更多
Numerical method is used to simulate the air breathing near the outlet of human nose. The process of breathing is visualized. The distribution of the exhausted air density may be useful in designing the medical equipm...Numerical method is used to simulate the air breathing near the outlet of human nose. The process of breathing is visualized. The distribution of the exhausted air density may be useful in designing the medical equipments.展开更多
An impeller is the most important component affecting the performance of centrifugal fans. The flow in the impeller is very complicated, and the 3\|D viscous flow is difficult to simulate numerically. This paper prese...An impeller is the most important component affecting the performance of centrifugal fans. The flow in the impeller is very complicated, and the 3\|D viscous flow is difficult to simulate numerically. This paper presents a numerical method for simulating the flow in practical commercial impellers. The predictions are compared with experimentally measured fan performance results. The predicted total pressure and efficiency for two fan models, whose optimum designs were determined by this method, agree well with the measured data for the design flow rate. The results show that the aerodynamic and noise levels for these two models are excellent. The paper also presents several new ideas about the shape of the front plate and the blade flow pattern to improve the flow in an impeller channel. The practical simulation methodology and results developed here will be very useful to the fan industry in the future.展开更多
A new lattice Boltzmann model for compressible flows is presented. The main difference from the standard lattice Boltzmann model is that the particle velocities are no longer constant, but vary with the mean velocity ...A new lattice Boltzmann model for compressible flows is presented. The main difference from the standard lattice Boltzmann model is that the particle velocities are no longer constant, but vary with the mean velocity and internal energy. The adaptive nature of the particle velocities permits the mean flow to have a high Mach number. The introduction of a particle potential energy makes the model suitable for a perfect gas with arbitrary specific heat ratio. The Navier Stokes (N\|S) equations are derived by the Chapman Enskog method from the BGK Boltzmann equation. Two kinds of simulations have been carried out on the hexagonal lattice to test the proposed model. One is the Sod shock tube simulation. The other is a strong shock of Mach number 5 09 diffracting around a corner.展开更多
文摘A cell centered scheme for three dimensional Navier Stokes equations, which is based on central difference approximations and Runge Kutta time stepping, is described. By using local time stepping, implicit residual smoothing, a multigrid method, and carefully controlled artificial dissipative terms, good convergence rates are obtained for two and three dimensional flows. The emphases are on the implicit smoothing and artificial dissipative terms with locally variable coefficients which depend on cel...
基金financially supported by the National Natural Science Foundation of China(Grant No.51349011)the Foundation of Si’chuan Educational Committee(Grant No.17ZB0452)+1 种基金the Innovation Team Project of Si’chuan Educational Committee(Grant No.18TD0019)the Longshan Academic Talent Research Support Program of the Southwest of Science and Technology(Grant Nos.18LZX715 and 18LZX410)
文摘In order to solve unsteady incompressible Navier–Stokes(N–S) equations, a new stabilized finite element method,called the viscous-splitting least square FEM, is proposed. In the model, the N–S equations are split into diffusive and convective parts in each time step. The diffusive part is discretized by the backward difference method in time and discretized by the standard Galerkin method in space. The convective part is a first-order nonlinear equation.After the linearization of the nonlinear part by Newton’s method, the convective part is also discretized by the backward difference method in time and discretized by least square scheme in space. C0-type element can be used for interpolation of the velocity and pressure in the present model. Driven cavity flow and flow past a circular cylinder are conducted to validate the present model. Numerical results agree with previous numerical results, and the model has high accuracy and can be used to simulate problems with complex geometry.
文摘Numerical method is used to simulate the air breathing near the outlet of human nose. The process of breathing is visualized. The distribution of the exhausted air density may be useful in designing the medical equipments.
文摘An impeller is the most important component affecting the performance of centrifugal fans. The flow in the impeller is very complicated, and the 3\|D viscous flow is difficult to simulate numerically. This paper presents a numerical method for simulating the flow in practical commercial impellers. The predictions are compared with experimentally measured fan performance results. The predicted total pressure and efficiency for two fan models, whose optimum designs were determined by this method, agree well with the measured data for the design flow rate. The results show that the aerodynamic and noise levels for these two models are excellent. The paper also presents several new ideas about the shape of the front plate and the blade flow pattern to improve the flow in an impeller channel. The practical simulation methodology and results developed here will be very useful to the fan industry in the future.
文摘A new lattice Boltzmann model for compressible flows is presented. The main difference from the standard lattice Boltzmann model is that the particle velocities are no longer constant, but vary with the mean velocity and internal energy. The adaptive nature of the particle velocities permits the mean flow to have a high Mach number. The introduction of a particle potential energy makes the model suitable for a perfect gas with arbitrary specific heat ratio. The Navier Stokes (N\|S) equations are derived by the Chapman Enskog method from the BGK Boltzmann equation. Two kinds of simulations have been carried out on the hexagonal lattice to test the proposed model. One is the Sod shock tube simulation. The other is a strong shock of Mach number 5 09 diffracting around a corner.
