Suction and oscillatory blowing flow control of external store support system flight hardware

This paper describes the development of a suction and oscillatory blowing (SAOB) active flow control (AFC) system, that was aimed towards achieving drag-reduction in a full-scale rotorcraft flight-test environment. The experimental work presented here includes benchtop characterization of the AFC actuators, development and testing of the AFC system using a full-scale two-dimensional airfoil at Tel Aviv University, and full scale testing of a UH-60 External Stores Support System (ESSS) in the CCDC AvMC Aviation Development Directorate 7- by 10-ft wind tunnel up to 140 knots. The airfoil tests composed of two stages, steady suction through holes on the trailing edge and the addition of pulsed blowing using SAOB actuators. The steady suction testing focused on identifying the optimal suction locations, while the SAOB experiments validated the suitability of the chosen actuator arrays to obtain the desired drag reduction at reasonable energetic cost. Tests for both steady suction and SAOB actuators resulted in 15-30% drag reduction compared to the clean baseline on the two-dimensional ESSS airfoil. Results from testing the full-scale ESSS identified the complexity of this configuration and the difficulty of transitioning directly from 2D component testing to three-dimensional testing of actual flight hardware. It became evident that by placing SAOB actuators only on the ESSS wing section, only 2-3% drag reduction was achievable. Further study is on-going to better understand aerodynamic interactions and develop a path towards more robust drag reduction.