OPTICAL RESEARCH OF THE PECULIARITIES OF THE FLOW AROUND MODELS WITH LOCAL SUPERSONIC ZONES IN INDUSTRIAL ADT T – 128

The paper discusses the results of the effective application of the method of spatial visualization of the flow around models in industrial ADT T - 128, combined with standard weight tests. Visualization of flow over the model was performed by varying humidity and temperature of the flow in test section. The results of a consistent standard weight experiment and a physical study of the characteristics of the flow around an aerodynamic model in an industrial ADT T - 128 are presented. In standard weight tests using video methods, the complex flow structure arising from the flow around an aerodynamic model at subsonic and transonic speeds is investigated. The results of balance measurements with simultaneous application of the method of spatial flow visualization around model in industrial T - 128 wind tunnel allowed to obtain physical information on the flow structure - a shock-waves, flow separation, wing vibration and deformation, the onset of asymmetric vortices. This greatly allows to expand the information content of experimental studies, to increase their reliability and to give a correct interpretation of the results obtained.

Strakes Effects on Asymmetric Flow Over a Blunt-Nosed Slender Body at a High Angle of Attack

In general speaking, the missiles execute flight at high angles of attack in order to enhance their maneuverability. However, the inevitable side-force, which is caused by the asymmetric flow over these kinds of traditional slender body configurations with blunt nose at a high attack angle, induces the yawing or rolling deviation and the missiles will lose their predicted trajectory consequently. This study examines and diminishes the side-force induced by the inevitable asymmetric flow around this traditional slender body configuration with blunt nose at a high angle of attack (AoA = 50 deg). On one hand, the flow over a fixed blunt-nosed slender body model with strakes mounted at an axial position of x/D = 1.6–2.7 is investigated experimentally at α = 50 deg (D is the diameter of the model). On the other hand, the wingspan of the strakes is varied to investigate its effect on the leeward flow over the model. The Reynolds number is set at ReD = 1.54 × 105 based on D and incoming upstream velocity. The results verify that the formation of asymmetric vortices is hindered by the existence of strakes, and the strake-induced vortices develop symmetrically and contribute to the reduction in side-force of the model. In addition, the increase in strake wingspan reduces asymmetric characteristics of the vortex around the model and causes a significant decrease in side-force in each section measured. The strake with the 0.1D wingspan can reduce the sectional side-force to 25% of that in the condition without strakes.

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

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.