Passive Reduction of Pressure Fluctuation by Using Cylindrical Rod on Open Cavity

Wind tunnel experiments and numerical simulations were performed on the cavity over a fuselage of an aircraft to investigate the control effect of passive control devices on pressure fluctuations. The experiments were conducted in subsonic flow, and the control effects of each passive control shape were compared and analyzed. The results indicated that the spoiler- and rod-type devices affect the pressure fluctuation differently, and the reduction effect is excellent when using the cylindrical rod. The changes in the flow structure due to passive control devices were numerically analyzed using unsteady turbulent flow simulation based on the improved detached eddy simulation (IDDES) model. Conditions similar to those in the wind tunnel experiment were applied, and the distribution and trend of the overall sound pressure level were in good agreement with the numerical results. The control effect in the transonic flow was analyzed using a cylindrical rod designed for subsonic flow. The energy cascade of the flow is accelerated due to the passive control device that makes the free shear layer to be unstable. Thus, the feedback mechanism is weakened. And finally, the pressure fluctuation inside the cavity is reduced.