Computation of Planar Store Trajectories Using an Adaptive Grid Procedure.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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The objective of this research was to compare a quasi-analytical, potential flowthree-degree-of-freedom model to an implicit-Euler algorithm for the calculation of store trajectories. The implicity algorithm uses a cell- centered, finite-volume, spatial discretization applied to the Euler equations, written in time-dependent, curvilinear-coordinates. A flux-differencing Roe scheme is employed to find the split-fluxes and the StegerWarming flux-vector method is used to calculate the flux-Jacobians. The potential flow and implicit- Euler algorithm are combined with a three-degree-of-freedom algorithm to evaluate the planar, freefall trajectories of a simple store shape. The research uses two different grid-modification techniques in the implicit algorithm evaluation. Data collected for both grids used the minimum time-step in the three-degree-of-freedom algorithm for a Courant number of 10. Two test cases involved updating the flux-Jacobians after every time-step and only once during every 1000 iterations. The effect of multiplying the minimum time-step by factors of 2, 4, 6, 8, 10, and 100 were also examined. The potential flow and implicit algorithm trajectories didnt compare very closely. The various Delta t and Jacobian-update results matched rather closely.