The performance of deflector jet servo-valve is
extensively influenced by the flow field characteristics inside
the pilot stage of the deflector jet servo-valve. Pressure
oscillations and cavitation phenomena commonly arise in the
deflector jet pilot stage that usually lead to high frequency
noises and vibrations of the servo-valve. To investigate this
issue and understand the internal flow characteristics of the
pilot stage, a three-dimensional numerical simulation is carried
out in this paper. The simulations are carried out using the
commercial ANSYS/FLUENT 18.2 CFD software. Large Eddy
Simulation (LES) coupling with cavitation model is utilized to
simulate the pressure oscillation phenomena and capture the
unsteady cavitation dynamics under several inlet pressures.
The result shows that the pressure oscillation phenomena
intensified by the increment of the inlet pressure. Moreover,
the characteristics of generating, growing, and merging cavity
shedding phenomena have been identified inside the pilot stage
of the deflector jet servo-valve. Finally, it can conclude that
pressure oscillation may one of the root cause of cavitation in
the deflector jet pilot stage.