Use of POD Method to Elucidate the Physics of Unsteady Micro-Pulsed-Jet Flow for Boundary Layer Flow Separation Control

This paper presents a micro pulsed aspirated jet concept to suppress the flow separation in compressors. According to this concept, a kind of pulsed jet and an imitating cascade channel has been established; the characteristic frequency of separation vortex is about 266Hz. The experimental and numerical investigation about the unsteady frequency has been finished, and when the frequency of pulsed jet is close to the characteristic frequency of separation vortex, the control effects are more obvious. Based on the numerical results, the proper orthogonal decomposition (POD) method is introduced to analyze the unsteady control mechanism, and the spatial and temporal structure of unsteady flow field can be decoupled by POD method. The POD analysis results show that the main effect of unsteady pulsed jet is reallocating the energy of each mode, and selectively strengthening or weakening certain modes; the effect of steady jet is overall reducing the energy of high order modes. Based on the reasonable control parameters of pulsed jet, the energy in higher modes will be transferred to the average flow mode, and the translation of modal energy is coming from the reconstructing of spatial flow structures and the ordering of modal evolution characteristic. Finally, the validation of experimental investigation has been finished; and the credibility of the analysis is also enhanced.