Rotor unsteady force suppression of a pump-jet by stator actuated oscillating trailing edge flaps: An experimental study for open-loop control

The magnitude of unsteady force generated by the rotor in pump-jet propulsors (PJP) directly determines the vibration and sound pressure levels of underwater vehicles. This study presents an experimental study on the unsteady force of a PJP incorporating stator actuated oscillating trailing edge flaps (AOTEF). The experiment was conducted in a water tunnel to evaluate the unsteady force control effect of an AOTEF-equipped behind a fully appended SUBOFF submarine model. Analyses have been performed on both rotor-induced unsteady force and the resultant structural vibration/underwater sound radiation. Experimental results demonstrate that under self-propulsion conditions at various flow velocities, the AOTEF can effectively suppress the unsteady rotor force and reduce both shaft vibration and radiated noise at blade passing frequency and its harmonics. The control performance is shown to depend primarily on the actuation phase and amplitude. The suppression mechanism is attributed to the AOTEF-induced modulation of the stator wake, which weakens the spatial non-uniformity of the rotor inflow and thus reduces periodic loading on the blades. These findings provide new experimental evidence and physical insight into the feasibility of active flow control for low-noise pump-jet propulsors.