Low Altitude Flow Field Numerical Simulation Of The Propeller-driven Aircraft

The computed space meshes with ground effect of general propeller-driven aircraft are created with an unstructured mesh technology. The slipstream boundary conditions are imposed at the surface swept by prop. The flow fields of the general propeller-driven aircraft are calculated by solving compressible Euler equations with numerical methods. The influences of ground effect, prop slipstream and attack angle of aircraft on the aerodynamics are researched. The unsteady aerodynamics of aircraft and wing moving up and down are simulated numerically.The figuration of general propeller-driven aircraft is modeled by the commercial software Gambit. The tetrahedral meshes with high quality are created in the computed space with advancing front method by the unstructured mesh creating technology developed by our project team. For researching the influence of ground effect on the aerodynamics of aircraft, the prismatic meshes with the same height near ground are added to space meshes of zero height from ground by an algebraic method. By extending or shrinking the prismatic meshes elastically, this method is used in the problem of unsteady aerodynamics of aircraft and wing moving up and down and it guarantees the high efficiency of mesh creation in the calculation of unsteady aerodynamics.The slipstream boundary conditions are imposed at the surface swept by prop to avoid the mass calculation of simulating the prop circumrotating with high velocity. The aerodynamics of aircraft can be simulated numerically by solving Euler equations exactly and efficiently. The compressible unsteady Euler equations are solved using the cell-centered finite volume spatial discretization and dual-time physical temporal derivatives. The first-order linearizing of flux vector and maximal eigenvalue splitting of flux Jacobi matrix are employed to construct an implicit Gauss-Seidel pseudo time-stepping relaxation iterative procedure. The standard convergence acceleration techniques such as local time stepping and implicit residual smoothing are adopted.The flow fields of propeller-driven aircraft at low altitude are calculated. The influences of ground effect, prop slipstream and attack angle of aircraft on the aerodynamics are researched and some regular and engineering significant conclusions are obtained. The numerical calculation results are accordant to the experimental data. It is shown that the method presented in this paper is feasible and correct, and this method has been already used in engineering.Finally, the unsteady aerodynamics of general propeller-driven aircraft and wing moving up and down are simulated numerically. The influence of ground effect on unsteady aerodynamics is investigated. Moreover, the influence of moving period on unsteady aerodynamics is also researched. Many conclusions with significant reference value in engineering are obtained.