Deriving Sensitivities of Distributed Propeller Propulsion in Overwing Configuration by using DoE in CFD Simulations

In this publication the interaction of propeller and wing of a short haul aircraft concept with distributed propeller propulsion in an over-wing configuration at cruise conditions is investigated. The numerical studies are performed in the CFD solver TAU of the German Aerospace Center using the Actuator Disk together with a wing segment with constant chord length. All calculations are performed in trimmed condition, i.e. with constant lift and drag coefficients. The resulting propeller power is used as a comparative variable. In order to quantify the influences of the position in chord direction, distance to the wing surface, installation angle, propeller diameter as well as distance between the propellers, a design of experiments approach with face centered central composite design is used. The resulting regression model is shown and analyzed. The procedure is carried out with two different propeller designs. In the first run, a propeller designed for a conventional aircraft with one propeller per half span is used. In the second run, a propeller designed for a distributed propulsion concept facing lower loads is used. The changes in the regression models are shown and compared. It hast been shown that the chord position has a significant influence on the performance of the propeller. The lowest power is reached when the propeller is positioned above the trailing edge of the wing. In addition, there is a dependence on the installation angle, which roughly follows the surface curvature of the airfoil. For the distance to the top of the wing, only a negligible effect on the propeller performance was found. For a positioning above the trailing edge, the propeller diameter and the spanwise distance between the propellers were found to be dominant parameters. Even when using a different propeller design, the linear dependence remains. For both propellers investigated, there is a similar optimal combination of diameter and spanwise distance with lowest power.