Impulsive Jets for Dynamic Stall Suppression*

Dynamic stall can occur on the retreating blade of a rotorcraft main rotor at high-speed forward flights with high disk loading. It limits the aerodynamic performance of the main rotor. Various flow-control techniques have been investigated for dynamic stall suppression. In the current study, impulsive jets are used for the stall control. Jets are generated from a combustion-powered actuator located on the suction side near the leading edge. The VR-12 airfoil is simulated with the compressible flow solver, SU2. A time-dependent boundary condition is implemented for impulsive jets. A pitching condition, relevant to the retreating-blade stall, is simulated in the current study. Unsteady RANS computations are conducted with the Spalart-Allmaras turbulence model. Current computational results show good agreement with the experimental data. Improved aerodynamic performances are observed in the downstroke of the pitching airfoil. Performance of the impulsive jet is compared to a steady-blowing jet with a similar time-averaged jet momentum. It is observed that the impulsive jet shows better performance than the steady-blowing jet does.