This paper describes a new method of calculation of one-dimensional steady compressible gas flows in channels with possible heat and mass exchange through perforated sidewalls. The channel is divided into small elemen...This paper describes a new method of calculation of one-dimensional steady compressible gas flows in channels with possible heat and mass exchange through perforated sidewalls. The channel is divided into small elements of a finite size for which mass, energy and momentum conservation laws are written in the integral form, assuming linear distribution of the parameters along the length. As a result, the calculation is reduced to finding the roots of a quadratic algebraic equation, thus providing an alternative to numerical methods based on differential equations. The advantage of this method is its high tolerance to coarse discretization of the calculation area as well as its good applicability for transonic flow calculations.展开更多
A mixed algorithm of central and upwind difference scheme for the solution of steady/unsteady incompressible Navier-Stokes equations is presented. The algorithm is based on the method of artificial compressibility and...A mixed algorithm of central and upwind difference scheme for the solution of steady/unsteady incompressible Navier-Stokes equations is presented. The algorithm is based on the method of artificial compressibility and uses a third-order flux-difference splitting technique for the convective terms and the second-order central difference for the viscous terms. The numerical flux of semi-discrete equations is computed by using the Roe approximation. Time accuracy is obtained in the numerical solutions by subiterating the equations in pseudotime for each physical time step. The algebraic turbulence model of Baldwin-Lomax is ulsed in this work. As examples, the solutions of flow through two dimensional flat, airfoil, prolate spheroid and cerebral aneurysm are computed and the results are compared with experimental data. The results show that the coefficient of pressure and skin friction are agreement with experimental data, the largest discrepancy occur in the separation region where the lagebraic turbulence model of Baldwin-Lomax could not exactly predict the flow.展开更多
A numerical method for solving isentropic compressible now problems is presented. This method uses the vorticity and the density as variables. The crux of the method lies in the numerical simulation of the process of ...A numerical method for solving isentropic compressible now problems is presented. This method uses the vorticity and the density as variables. The crux of the method lies in the numerical simulation of the process of vorticity and density variation. The fundamental equation of a compressible discrete vortex method is derived. Unlike the BiotSavart law in the incompressible fluids, the modified Blot-Savart law in compressible fluid should contain the change of the non-solenoidal. The change of density induces the variation of the fluid velocity. The effects of compressibility on flow past a circular cylinder have been investigated by using the compressible discrete vortex method at a Reynolds number of l.E+6. The Mach number is 0.5. The results show that the form of vortex shedding is different from the incompressible now. The separation positions shift upstream, the wake more wide and the street is not clear like the incompressible.展开更多
When there are several bodies with relative motion in a flow field,such as the flow in the compression system of modern aero-engine,the flow field will have certain special features,one of which is that the time-space...When there are several bodies with relative motion in a flow field,such as the flow in the compression system of modern aero-engine,the flow field will have certain special features,one of which is that the time-space structure of such multi-bodies unsteady vorticity flow field would be either of unsteady natural flow(UNF)pattern or of unsteady cooperative flow(UCF)pattern.If we further examine the aerodynamic design system of aero-engine,there is no mechanism for the unsteady cooperative flow to occur,in other words the flow field must be of the unsteady natural flow type.If certain technical measures can be adopted to transform UNF into UCF,the aerodynamic performances will surely be improved.This is the main task the author and their colleague have been devoted to and the results are reviewed in the present paper with emphases laid on basic ideas,technical approaches and experimental verifications.展开更多
文摘This paper describes a new method of calculation of one-dimensional steady compressible gas flows in channels with possible heat and mass exchange through perforated sidewalls. The channel is divided into small elements of a finite size for which mass, energy and momentum conservation laws are written in the integral form, assuming linear distribution of the parameters along the length. As a result, the calculation is reduced to finding the roots of a quadratic algebraic equation, thus providing an alternative to numerical methods based on differential equations. The advantage of this method is its high tolerance to coarse discretization of the calculation area as well as its good applicability for transonic flow calculations.
文摘A mixed algorithm of central and upwind difference scheme for the solution of steady/unsteady incompressible Navier-Stokes equations is presented. The algorithm is based on the method of artificial compressibility and uses a third-order flux-difference splitting technique for the convective terms and the second-order central difference for the viscous terms. The numerical flux of semi-discrete equations is computed by using the Roe approximation. Time accuracy is obtained in the numerical solutions by subiterating the equations in pseudotime for each physical time step. The algebraic turbulence model of Baldwin-Lomax is ulsed in this work. As examples, the solutions of flow through two dimensional flat, airfoil, prolate spheroid and cerebral aneurysm are computed and the results are compared with experimental data. The results show that the coefficient of pressure and skin friction are agreement with experimental data, the largest discrepancy occur in the separation region where the lagebraic turbulence model of Baldwin-Lomax could not exactly predict the flow.
文摘A numerical method for solving isentropic compressible now problems is presented. This method uses the vorticity and the density as variables. The crux of the method lies in the numerical simulation of the process of vorticity and density variation. The fundamental equation of a compressible discrete vortex method is derived. Unlike the BiotSavart law in the incompressible fluids, the modified Blot-Savart law in compressible fluid should contain the change of the non-solenoidal. The change of density induces the variation of the fluid velocity. The effects of compressibility on flow past a circular cylinder have been investigated by using the compressible discrete vortex method at a Reynolds number of l.E+6. The Mach number is 0.5. The results show that the form of vortex shedding is different from the incompressible now. The separation positions shift upstream, the wake more wide and the street is not clear like the incompressible.
基金the financial support received from the National Natural Science Foundation of China(Grant no.10902008)for this project.
文摘When there are several bodies with relative motion in a flow field,such as the flow in the compression system of modern aero-engine,the flow field will have certain special features,one of which is that the time-space structure of such multi-bodies unsteady vorticity flow field would be either of unsteady natural flow(UNF)pattern or of unsteady cooperative flow(UCF)pattern.If we further examine the aerodynamic design system of aero-engine,there is no mechanism for the unsteady cooperative flow to occur,in other words the flow field must be of the unsteady natural flow type.If certain technical measures can be adopted to transform UNF into UCF,the aerodynamic performances will surely be improved.This is the main task the author and their colleague have been devoted to and the results are reviewed in the present paper with emphases laid on basic ideas,technical approaches and experimental verifications.
