Research on the kinetics of rock motion for a missile model with strake wings

Numerical computations of coupled Navier-Stokes equations and flight mechanic equations are conducted to research and analyse the kinetic characteristics and mechanism of rock motion for a missile model with strake wings. Control equations are unsteady RANS and one-DOF rigid-body roll equation. Roe scheme, S-A turbulence model and dual time stepping techniques are selected to solve the URANS, and 3rd Adams prediction-correction method is used to couple the aerodynamic and flight mechanic computations. Calculation at Ma=0.6 and α=35° resulted in a Limited Cycle Oscillation (LCO) with amplitude of 10.14° and frequency of 20Hz which agree with wind tunnel test. The hysteresis loop of rolling moment coefficient is double 8 style and the total energy of aerodynamic force acting on the model is equal to zero during a period. Forces acting on different components show that the unstability is caused by the windward fins and cannot be compensated by the leeward fins, resulting in the loss of roll damping and the limit cycle oscillation. Computations validate that this LCO is stable, meaning that the model would enter into it by disturbances. It is also shown that the moment of inertia has little effect on the rock amplitude while has a significant effect on the frequency when the unsteady effect is strong.