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Abstract The performance of a deflector jet servo valve is highly affected by the characteristics of the pilot stage flow field. In this paper, the transient results of the large eddy simulation (LES)-based numerical simulation of the pilot stage flow field are presented. The LES results are validated against particle image velocimetry, showing that the LES method can predict the transient turbulent flow. The length of the potential core of the jet assuming from the nozzle and the position of the jet impinging on the V-groove have great relations with the inlet pressure. Traveling cavitation in the deflector begins to appear when the inlet pressure reaches 6 MPa. The increment in inlet pressure enhances cavitation and cavitation shedding. Snapshot proper orthogonal decomposition(snapshot POD) analysis, based on LES, is applied to decompose the instantaneous velocity fluctuation into coherent structures and turbulent velocity components. The relationships between each coherent structure and wall attachment flow, cavitation phenomena, and vortex pairs are discussed. The vortex in Mode 2 contributes to deflecting the jet from the nozzle and causing part of the fluid to flow along the side wall in the V-groove. Through the fast Fourier transform (FFT) result of the POD coefficient, it is known that the traveling cavitation near the side wall of the V-groove is related to Mode 4. This research contributes to the mathematical modeling and improving the stability of the flow field.
Wu et al. (Mon,) studied this question.