The lateral force hysteretic characteristic of a pitching slender body without and with synthetic jet control

Abstract

The lateral hysteretic characteristic generated by asymmetric vortical flow behind the tangent-ogive cylinder is investigated without and with micro synthetic jet control, when the slender body undergoes a large amplitude pitching motion. Experiments are conducted in a low speed wind tunnel of Nanjing University of Aeronautics and Astronautics at a Reynolds number of 46000. The change rule of the instantaneous pressure distribution reflects the aerodynamic characteristic of the whole model. The data of temporal flow file are acquired using particle image velocimetry locked-phase method and present the asymmetric vortices evolution. Results show that asymmetric vortices still exist in the leeward of the slender body during the dynamic pitching motion. However, the asymmetric degree of the vortices distribution, swirling strength and breakdown location are different which is greater in the downward pitching than in the upward pitching, which leads to the lateral force hysteretic phenomenon. In addition, the hysteretic loop expands as the reduced frequency increased. It is an effective method of the flow control that uses micro synthetic jet alternative blow to control the lateral force in the dynamic pitching motion. Furthermore, the lateral force, the pressure distribution and the hysteretic loop shape are changed continuously as the duty cycle of the control signal increased. For the duty cycle of 50%, the vortices distribution, the swirling strength and breakdown location tend to be symmetrical, so the lateral force decreases significantly and the hysteretic loop is eliminated.