CFD - flight mechanics simulations still suffer from the large resources required. That is the main motivation for setting up new techniques for predicting store trajectories. In the present study, a novel approach based on CFD simulations on compact domains is suggested. The basic idea proposed here is to split the CFD simulation in two parts with its own grids. The first large primary grid is called the global domain. This grid contains the airplane, from which the cargo drops. The other part, a smaller CFD grid, is the so called compact domain, on which the coupled CFD - flight mechanics (CFD-FM) simulation is performed. The steady CFD simulation on the global domain delivers the boundary conditions for the compact flow domain, on which the unsteady CFD-FM simulation for the flow and maneuver of the separating cargo are conducted. A very essential point for the performance of the whole process chain is the interpolation between global and compact domains and, in special cases, the used grid overset technique, behind. By considering a simple airfoil example the principles of the proposed approach are demonstrated. Thereafter, the validity and efficiency of the presented approach are investigated and assessed against unsteady CFD-FM simulation on the basis of the separation of an Unmanned Combat Aerial Vehicle (UCAV) out of a future military transport aircraft. Furthermore, different scenarios of the separation of the UCAV are computed in order to study the feasibility of such a process. The results of the developed approach are promising both in terms of accuracy and wallclock runtimes.
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