Numerical study of the effect of micro vortices on chaotic flutter

Abstract

The loading generated by shock wave boundary layer interaction (SBLI) plays a crucial role in the structural design of a high-speed vehicle. They can cause flow separation near the shock impingement, resulting in the onset of chaotic, self-sustained flutter leading to structural failure. This work investigates how a micro-ramp installed upstream of a flexible panel affects its flutter behavior. For this purpose, two-way coupled laminar fluid–structure interaction simulations are performed for two different oblique shock strengths impinging over a flexible panel. A comprehensive study with a micro-ramp, as high as half the boundary layer thickness, is conducted for a wide range of non-dimensional dynamic pressures expected for a supersonic flight. The study provides analysis methodology to characterize the nature of panel oscillations, and the influence of micro-ramp on fluid and structural unsteadiness is evaluated. The results indicate that the chaotic flutter is initiated because of the non-linear interaction between the high-frequency fluid and low-frequency structural unsteadiness. Micro vortices delay the onset of the chaotic flutter by lowering the fluid frequency, thereby synchronizing fluid and structure unsteadiness. The micro vortices also decreased flutter frequency for lower shock strength; however, MVG was somewhat ineffective for some higher shock strength. For the latter taller micro-ramps that can introduce stronger, low-frequency vortices are recommended.