Influence of slenderness ratio on the lateral force of a slender body at high angle of attack

Abstract

The slenderness ratio is an important feature of the slender body, but the effect of slenderness ratio on the lateral force of the slender body at high Angle of attack have not clearly. In this paper, the Detached eddy simulation (DES) method is verified and adopted to simulate the flow of five models with slenderness ratio SR=10, 12.5, 15, 17.5 and 20. The simulation is carried out under the conditions of 15.3m/s incoming flow and 55° Angle of attack. Based on the simulation results, the vorticity magnitude and surface pressure coefficient of the five models are compared. It is concluded that the increase of slenderness ratio will increase the fluctuation cycle of pressure along the axial direction. To further analysed the relationship between pressure distribution and lateral force in different models, the pressure values of multiple sections were extracted and integrated to draw the change curve of unit lateral force coefficient along the X direction. From the analysis of unit lateral force coefficient, the difference of pressure between the two sides induced by asymmetric vortex at the head is the main source of lateral force. The unit lateral force coefficient (Cfzpm ) of the model with small slenderness ratio oscillated more dramatically and attenuated more slowly than that of the model with large slenderness ratio, due to the interaction between the head vortex and the high-pressure region at the bottom of body with a small slenderness ratio at a large Angle of attack. The interaction between the head vortex and the bottom high-pressure region makes the lateral force coefficient of the model with small slenderness ratio not necessarily significantly smaller than that of the model with large slenderness ratio. With the increase of slenderness ratio, the influence of head vortex on the pressure distribution of rear surface decreases, and the asymmetry of rear surface pressure distribution decreases. The conclusion of this paper can help to solve the problem of lateral force coefficient variation that may occur in multistage rocket engineering.