Computational Fluid Dynamics Analyses of Flow over Weapons-Bay Geometries

Abstract

Detached-eddy simulations for the M219 experimental cavity geometry and the 1303 uninhabited combat air vehicle cavity geometry are presented. First, results from three computations are presented with the aim of studying the effect of imposing synthetic velocity fluctuations at the inflow boundary. Both methods employed (synthetic-eddy method and fluctuations from a precursor large-eddy simulation) increased the high-frequency content in the boundary layer upstream of the cavity. Averaged profiles showed little change in the streamwise velocity; however, the profiles of normal velocity were noticeably different. The influence of the upstream boundary layer on the cavity flowfield means that the full aircraft geometry needed to be modeled. Consequently, advanced multiblock topologies had to be used to properly represent the planform of the uninhabited combat air vehicle and all the details of the cavity, including doors and hinges, while sliding meshes were needed to insert the store into the uninhabited combat air vehicle configuration. Results with an empty cavity were encouraging for such complex configurations. Visualizations using the Q criteria revealed the added turbulent content due to the door leading edges and the door hinges. The addition of a store in between the doors had little effect close to the front wall. However, averaged flowfields showed that the proximity of the shear layer to the apex of the store deflected it downward into the cavity and restricted its growth. Outside the cavity, shedding was observed from the sting and force balance.