Detached eddy simulation of weapons bay flows and store separation

• Unsteady fluctuating flow characteristics inside a cavity.
• Effect of turbulence model.
• Effect of cavity flow unsteadiness on internal stores.
• Effect of cavity flow on initial directivity and trajectory of free-flight stores.
• Effect of blowing as a mean of flow control on cavity flow and separating stores.

When internal weapons bay is exposed to free-stream, highly unsteady flow-field is formed over and inside the bay. The pressure fluctuation may cause damages on the surrounding structures, and increases noise. The complicated aerodynamic characteristics inside the weapons bay also affect the behavior of the stores released from the weapons bay. In the present study, numerical investigations of the unsteady flow-fields inside a weapons bay were conducted by using a three-dimensional compressible flow solver based on unstructured meshes. The effects of fluctuating flow inside the cavity on the aerodynamic loads of the store were also studied. Then simulations of the stores separating from the cavity were carried out, and the effect of flow unsteadiness on the store trajectory was examined. Finally, steady blowing was applied to suppress the pressure fluctuation and to help stabilizing the store separation. It was shown that flow unsteadiness inside the cavity is mainly caused by the detaching and reattaching process of the shear layer. It was found that the results of the SST–DES simulation are in better agreement with experiment in predicting high frequency flow contents than those of the k–ω SST turbulence model. When the store is located inside the cavity or at the shear layer, the pressure on the store oscillates in time. As a result, the trajectory of the store during the initial separation stage is significantly affected depending on the release point in time. It was demonstrated that steady blowing is an effective mean for mitigating the pressure fluctuation and stabilizing the store separation.