Calculation of the Propulsive Efficiency for Airships with Stern Thruster
Th. Lutz, P. Funk, A. Jakobi and S. Wagner
14th AIAA Lighter-Than-Air Technical Committee Convention and Exhibition, Akron, Ohio, USA, July 15-19, 2001
A method for the aerodynamic analysis of bodies of revolution with a stern propeller was developed. The viscous flow about the displacement body is determined by a panel method in combination with an integral boundary-layer procedure. Special emphasis is laid on the iterative viscous/inviscid coupling. For this purpose the transpiration technique is applied along with an under-relaxation scheme. The relaxation factor is determined from a local stability analysis of the coupled governing equations. A vortex sheet model is used to calculate the time-averaged influence of the propeller with a fully-relaxed slipstream. Both modules are coupled taking viscous interaction effects into account. The complete tool was applied to analyse airship hulls with stern-mounted thrusters and finally to predict the increased efficiency of wake propellers.