Validation and Comparison of RANS Propeller Modeling Methods for Tip-Mounted Applications

The potentially favorable interaction of a propeller slipstream with a wingtip is a complex problem, because of the importance of vortex interaction and viscous effects. This paper examines the capability of different propeller modeling methods in a Reynolds-averaged Navier-Stokes (RANS) solver for the simulation of wingtip-mounted propellers. The applicability of actuator-disk and actuator-line models to reduce the cost of propeller modeling is investigated in its most accurate form, by applying propeller-blade-loading results extracted from simulations, in which the blades are fully resolved. The numerical results are validated by comparison with measurement data from in-house wind-tunnel experiments. It is concluded that the aerodynamic interactions for the wingtip-mounted propeller in tractor configuration can be predicted by RANS simulations with a simple one-equation turbulence model (Spalart-Allmaras), provided that the uncertainty due to numerical diffusion is accounted for by a grid-dependency study, or reduced by local grid refinement. The actuator-line model reduced the computational time by 17% without introducing errors into the time-accurate and time-averaged wing loading. The actuator-disk model reduces the computational cost by 85% by removing time dependency, with a small penalty in the accuracy of the time-averaged flowfield and a 3.9% overprediction of the wing lift.