Numerical investigation of aerodynamic effects of opposite wrap-around fins at supersonic speeds

Abstract

In this research work, using numerical simulations, the three-dimensional flow around a standard projectile is investigated with two fin arrangement models, namely opposite and conventional wrap-around fins. Eliminating the rolling moment and investigation of aerodynamic performance of the new geometries are the purpose of this paper. Finite volume method is used to undertake the numerical simulations where flow is considered to be compressible, steady, nonviscous, and three-dimensional. For this purpose, the research begins with simulating the flow around a projectile with conventional fin arrangement and then the obtained values of drag coefficients and rolling moment are compared against experimental data, indicating the validity of the simulation results. After then, the effect of wrap-around fins in an opposite arrangement is investigated, with the results compared against those of the conventional configuration. The opposite fins are investigated at different opening angles and joint position, while the area of fins shading is assumed constant in all cases. Simulations were conducted at three Mach numbers of 1.5, 2.5, and 3.5, different angles of attack ranging within 0–14°, and lateral wind angles up to 8°. According to the results, the rolling moment in conventional wrap-around fins is a result of the pressure difference between sides of the fins, so that it can be avoided by configuring the fins in an opposite arrangement, which contributes to slightly higher drag coefficients too. Fin dimensions and their opening angle influence the regime of the flow passing through the fins, making their aerodynamic performance variable at different Mach numbers.