Turbulent flow and acoustic predictions over open cavity configurations at transonic speeds

Çoşkun, Seyfettin.
In modern military fighters, internal carriage of weapons is vital in terms of high survivability, low observability and aerodynamic performance of the fighter. During store release phases of operation, the aircraft will have to fly with the cavity exposed to free stream conditions. When an aircraft internal weapons bay is exposed to free stream of air, a highly unsteady and complex flow field develops within the cavity. This triggers intense aero-acoustic environment in and around the cavity. Highly complex, unsteady and nonlinear flow environment of a cavity may cause possible structural, acoustic and aerodynamic problems such as fatigue in structures, nose-up pitching moment on stores, resonance in cavity walls and etc. Therefore, it is desired to assure that internal stores, aircraft structures and internal weapon bay (IWB) structureandequipmentinsidetheIWBcanwithstandthisharshenvironmenttosuccessfully complete the mission under required conditions. In this respect, various cavity configurations such as clean cavity (i.e. no stores, no doors etc.), cavity with a generic store, cavity with doors and doors at different orientations are analyzed for the effects of each configuration on cavity acoustic characteristics. Unsteady Reynolds-Averaged(URANS) and Detached Eddy Simulation (DES) turbulence model variants available in ANSYS/Fluent solver are utilized. It has been found out that although URANS models can predict the OASPL trends within the cavity with a level of accuracy, they are lack of accuracy in capturing the frequency spectra due to averaging nature of URANS models. On the other hand, IDDES model is quite successful in predicting both the noise intensity and the frequency spectra of various cavity configurations at transonic speeds.
Citation Formats
S. Çoşkun, “Turbulent flow and acoustic predictions over open cavity configurations at transonic speeds,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Aerospace Engineering., Middle East Technical University, 2019.