Modelling the influence of streamwise flow field acceleration on the aerodynamic performance of an actuator disc

Abstract. In the present work, a simple model is derived for the situation of an actuator disc (AD) operating in a background flow field featuring a constant streamwise velocity gradient. Reynolds-averaged Navier-Stokes (RANS) simulations of this scenario are performed, showing that a positive acceleration yields a reduction of induction and vice versa, a negative acceleration leads to an increase of induction. The new model accurately captures this behavior and significantly reduces the prediction error compared to classical momentum theory, where the effect of the background flow acceleration is disregarded. The model indicates that the maximum power coefficient and the corresponding values of the optimal induction and thrust coefficient depend on the flow acceleration.