基于变步长CFD/RBD方法的旋转弹轨迹仿真

采用变步长方法实现非定常Navier-Stokes方程和刚体六自由度运动方程的耦合求解,并对美国ARL旋转弹试验模型的飞行轨迹进行了仿真。旋转弹自由飞行过程中受到空气阻力作用,转速下降,气动力变化趋缓。因此轨迹仿真时先选取较小的时间步长,随着转速的下降逐渐增大步长,这样可以减少计算时间。刚体六自由度运动方程的数值求解采用变步长Adams预估校正法。将定步长和变步长两种方法应用于旋转弹实验模型轨迹仿真,并将计算得到的旋转弹空间位置、姿态角与试验结果进行了对比,结果显示:方法能较精确地仿真旋转弹飞行轨迹。在相同初始步长条件下,变步长方法较定步长方法计算时间减半;在相同计算时间条件下,变步长方法较定步长方法精度更高。

Trajectory Simulation of a Spinning Projectile Based on CFD/RBD Computation Method

The unsteady Navier-Stokes equation and rigid body equations of 6-DOF motion are solved u-sing variable-step coupling computation method to simulate and analyze the flight trajectory of U .S.Army Research Laboratory spinning projectile test model .During the free-flight process ,aerodynamic resistance has significant effect on the projectile motion causing decrease in its revolution which eventually decreases the unsteady aerodynamic load .The initial time step-size of trajectory simulation is chosen small ,which is then gradually increased corresponding with the decreasing revolution .This approach assists in reducing the computational time .The rigid body equations are solved using variable-step Adams prediction-correc-tion method.Both variable-step and fixed-step methods are applied to compute positions ,orientations of the spinning projectile test model .Computed results are found to be generally in good agreement when compared with experiment data .For the same initial step-size , the computational time for the variable-step method is reduced by half of that of the fixed-step method .Also for the same computational time the variable-step method is more accurate .