Experimental and numerical research on vortex street flow oscillation characteristics in pre-stage of deflector jet servo valve

Pressure oscillations in the pre-stage of a deflector jet servo valve are investigated using a combination of numerical simulations and flow visualization experiments, focusing on the oscillation mechanism and the variation characteristics of the dominant frequency. The results reveal the presence of a pronounced vortex street oscillation within the pre-stage. When the jet impinges on the V-shaped region, a wall jet is formed accompanied by symmetric recirculation zones on both sides. The instability induced by the interaction between the primary jet and the recirculating flow leads to the periodic formation, growth, and shedding of vortical structures, which in turn drive the self-sustained oscillatory deflection of the jet. The dominant frequency increases with inlet pressure, while variations in key geometric parameters can significantly influence both the oscillation modes and dominant frequency. Dimensional analysis shows that the oscillation frequency can be described by a dimensionless parameter constructed from pressure and geometric scales, providing a theoretical basis for the structural optimization of the pre-stage.