Computation of unsteady transonic flow over a fighter with using a zonal Navier-Stokes/full-potential method

摘要

An improved hybrid method for computing unsteady compressible viscous flows is presented. This method divides the computational domain into two zones. In the inner zone, the Navier-Stokes equations are solved using a diagonal form of analternating-direction implicit (ADI) approximate factorisation procedure. In the outer zone, the unsteady full-potential equation (FPE) is solved. The two zones are tightly coupled so that steady and unsteady flows may be efficiently solved.Characteristic-based viscous/inviscid interface boundary conditions are employed to avoid spurious reflections at that interface. The resulting CPU times are about 60% of the full Navier-Stokes CPU times for unsteady flows in non-vector processingmachines. Applications of the method are presented for a F-5 wing in steady and unsteady transonic flows. Steady surface pressures are in very good agreement with experimental data and are essentially identical to the full Navier-Stokes predictions.Density contours show that shocks cross the viscous/inviscid interface smoothly, so that the accuracy of full Navier-Stokes equations can be retained with significant savings in computational time.