Inviscid Computation of the Effect of Wake Vortices on the Model Airplane

Abstract

Within the EU-project WAVENC the block structured DLR-FLOWer code has been applied to the inviscid simulation of a wake vortex encounter of a generic aircraft. Two classes of methods of different physical accuracy have been assessed. The more advanced method, the so-called method of vortex transport meshes, allows a mutual interaction between the vortices and the airplane. The incoming vortices of the preceding aircraft are prescribed at the inflow boundary of the computational domain. In order to transport the vortices without too big numerical losses from the inflow boundary to the aircraft, very fine Cartesian grids, so "called vortex transport meshes", have been embedded into the grid structure. This is enabled by the Chimera technique implemented in the code. On the other side, two methods with a simplified prescription of the incoming vortices of the preceding aircraft are tested. These account only for the influence of the vortices on the airplane; the influence of the airplane on the vortices is neglected, which might be a problem in cases of strong interactions. The results obtained with FLOWer using both philosophies were compared to the experimental data of an encounter experiment as well as to the numerical results of other Euler codes. Additional comparisons to the results of panel methods applied in the WAVENC project were carried out. Global forces and moments as well as pressure distributions obtained for different positions of the aircraft in the vortex disturbed flowfield show a good agreement to experimental data. The advantages of the method of vortex transport meshes become visible, if a vortex trajectory of the incoming vortices is close to the fuselage of the following aircraft.