Parametric Investigation of Flow over a Rotor-Blown Wing using High-fidelity Simulations

This study models an infinite rotor-wing unit based on the CRC-20 quad-rotor bi-plane at an angle of attack of 8^◦ and rotor modeled using the actuator line method (ALM). Parametric variations to the rotor-wing geometry are considered. These include rotor-wing chordwise separation, rotor-wing vertical offset and rotor-rotor spanwise separation. Large eddy simulation (LES) and delayed detached eddy simulation (DDES) approaches with and without the transition model are used to analyze the baseline configuration. DDES with the transition model is found to compare well with LES and is selected for the parametric study to balance the computational cost. Compared to isolated wing and rotor cases, baseline rotor-wing case shows 5.46% lower power loading, 14.42% higher lift and 4.45% higher L/D ratio. From the parametric study, varying the rotor-wing chordwise spacing did not significantly influence rotor power loading but placing rotor further from the wing improved L/D ratio by 7.64% compared to baseline due to reduction in sectional drag. The rotor-wing vertical offset cases show that placing the rotor below the wing significantly reduces the L/D ratio while placing it above yields similar L/D ratio to baseline but lowers the power loading by 6.69%. Finally, the spanwise rotor-rotor separation cases show that higher separation yields a 5.66% improvement to L/D ratio with no effect on the rotor power loading, again due to reduction in sectional drag.