Numerical Study Of Combined Perturbation Control Of Asymmetric Vortices On A Slender Body Of Revolution At High Angle Of Attack

Regarding to the problem of asymmetric flow over a slender body of revolution at high angle of attack, the three-dimensional compressible Navier-Stokes equations have been solved to investigate the combined perturbation technique for control of the bistable flow at attack angle of 50°. The numerical results have been analyzed to discuss the role of the spatial instability mechanism played in the asymmetric flow control.The results show that the combined perturbation technique is effective to make the side force vary smoothly under the bistable flow situation. Because this flow is highly sensitive to the small disturbance near the nose, the control parameters including the circumferential angle of the geometric bump, the axial location of the blowing port and the circumferential angle of the blowing port play important roles in side force control effects, which manifests in the following aspects. Firstly, the circumferential angle of the geometric bump could determine whether it is the left-side or the right-side vortex pattern. Secondly, the control technique is effective only when the blowing port is located at the same side with the low primary vortex. Finally, when the blowing port is located at an appropriate position near windward symmetry plane or at an appropriate distant from the nose, it would be helpful to reduce sensitivity of the flow field to the combined perturbation parameters as well as improve the smoothness of the side force variation.Through the research of side-force response to the combined perturbation and the growth of the disturbance energy along the slender body, it is revealed that the spatial instability character of the flow is the physical fundament of the successful implementation of the combined perturbation technique. This technique generates an initial vortex pattern by providing an appropriate combined perturbation intensity, and then the nose perturbation is amplified spatially which results in the formation of corresponding regular or transitional flow. If an appropriate location of the blowing port was adopted, the extent of blowing-moment coefficient in which the disturbance energy curves contain distinct exponential growth regime would be enlarged, which confirm the feasibility of improving the smoothness of the side force variation by seeking an appropriate location of the blowing port.