Diffuser Optimization with Active Flow Control: Steady vs. Unsteady Simulation Approaches

Abstract

To promote the continuous evolution of aircraft design, it is essential to incorporate advanced aerodynamic techniques. In this context, the deployment of Active Flow Control (AFC) is crucial for effectively suppressing flow separation. Minimizing the energy consumption of the AFC system necessitates the use of unsteady methods. Pulsed jet actuators (PJA) present a promising solution. However, their working principle conflicts with the state-of-the-art CFD design method, namely Reynolds-Averaged Navier-Stokes (RANS), which relies on the steady-flow assumption to maintain practical computational efforts. Given that current computational resources are insufficient for time-resolved simulations in industrial design processes, it is important to assess the potential limitations of the steady-flow assumption in certain applications. This study aims to examine the significance of the steady-flow assumption in the design process of PJA flow control. Additionally, the impact of this assumption on the estimated global flow performance parameter is analyzed. A test case is developed, and the impact of the unsteadiness of the PJAs is investigated by comparing steady and unsteady simulation results, including unsteady RANS (uRANS) and Delayed Detached Eddy Simulation (DDES). This investigation aims to conclude whether unsteady flow control can be efficiently designed using steady simulations.