Analysis of kinematic characteristics of square cross section vehicle at multi-trim angle of attack

Abstract

The velocity range of vehicle is quite considerable from launch phase to cruise phase, and the stability would be significantly altered with the change of Mach number, even worse, the number of trim angle of attack may be altered in some cases. Variety of kinematic characteristics is studied using the numerical simulation method on a square cross section vehicle which was changed from stable to instable, from one trim angle of attack to three trim angles of attack with the increase of Mach number. The simulation results show the existence of the critical Mach number Mcr in the aspect of stability. The vehicle is stable nearby the unique equilibrium point where Ma is smaller than Mcr ; otherwise, the number of equilibrium points would increase to three, the pre-equilibrium point is instable and the two new equilibrium points are stable. The saddle-node bifurcation phenomenon will take place in the pitching motion of the vehicle in case of having three equilibrium points, and the final convergent position is extremely sensitive to the variety of initial condition. The pitching motion could be convergent to one trim angle of attack under certain conditions, but the convergence may alter to the other trim angle of attack with little change in the initial conditions.