Principal invariants of acceleration gradient tensor and their statistics in compressible channel flow

In this study, we utilize the acceleration gradient tensor (AGT) as a tool to probe turbulence. It is demonstrated that the AGT principal invariants include not only the spatial characteristics described by the velocity gradient tensor, but also the evolution features such as the temporal evolution of dilatation, strain rate, and rotation rate. Based on the statistical differences in AGT invariants within the viscous sublayer of compressible channel flow, it is confirmed that alternating positive and negative structures near the wall in high-speed flows with strong compressibility induce intense temporal evolution of dilatation.