Numerical Simulation of Air Launch Aeroelasticity with Random Variation of Aerodynamic Loading Parameters

The problem of safe air launch vehicle descent from heavy airlifter cargo bay is considered. The influence of aircraft fuselage vortex wake on the descend dynamics is studied. Three-dimensional incompressible flow is considered. The coupled fluid - structure interaction problem is solved. Vortex element method with new vortex element - vortex cell for unsteady flow dynamic simulation is used. The elastic-mass model of the vehicle and launcher is taken into account. Aim of this work is to study influence of wake stochastic characteristics on the unsteady aerodynamic loads and on kinematic parameters of launch vehicle motion. Stochastic analysis method is used to define the boundaries of kinematic parameters’ variation region. The probability of hitting a random event into the region with boundaries is found to be almost equal to the probability of a certain event. An original algorithm with moderate computational cost is presented for determining the boundaries of the parameter variation region. Numerical simulation results are obtained for variation regions of linear and angular displacements boundary of heavy launch vehicle prototype. It is shown that random variation of the wakes initial state gives a significant variation region for kinematic parameters of the vehicle, not only in the pitch plane, but also in the yaw plane so that the worst-case combination of parameters can lead to emergency.

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