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Spatial and temporal dynamics of a supersonic mixing layer with a blunt base

Li, Lantian; Li, Hao

Inst. Strömungsmechanik und Technische Akustik (ISTA)

A supersonic mixing layer with a blunt base is of practical significance to engineering. Two flow configurations with splitter thicknesses of 1 mm (TN) and 5 mm (TK) are simulated using large eddy simulation. The cluster-based network model (CNM) projects the supersonic mixing layer into a ten-centroid based low-dimensional dynamical system. The CNM’s outputs of TN and TK cases are compared in order to better understand the spatial and temporal physics. The given baseline case (TN) demonstrates a quasi-steady dynamics with a periodic visit between ten centroids. Each cluster occupies a nearly uniform space region and is also populated with equal probability. The CNM identifies ten centroids associated with these two flow regimes observed in the TK case: Kelvin–Helmholtz vortex and vortex pairing. According to the resolved centroids, increasing the thickness of the splitter plate complicates the flow structures and expands the high-dimensional state space. The CNM presents probable state transitions, revealing that the temporal dynamics in the whole field exhibits highly intermittent behaviors, with large shape modifications but small fluctuations in turbulent kinetic energy. In the near-wake field, the reattachment point and shock wave behave similarly that they move downstream and upstream alternatively. The blunt base supersonic mixing layer, in aggregate, increases the turbulent kinetic energy by 20.5%.