2D-2C Particle Image Velocimetry analysis of contra-rotating propellers hydrodynamics

Contra-rotating propellers represent a non-conventional approach for marine propulsion whose main advantage lies in the increase of propulsive efficiency. This is achieved by recovering part of the energy loss due to the rotational flow generated by a single propeller by means of a contra-rotating downstream propeller. The hydrodynamics of such configuration is quite complex due to the interaction between upstream and downstream propellers and a deep understanding of their features is critical to driving the design phase. In this work a methodology based on planar (2D-2C) Particle Velocimetry is presented to investigate on the flow in the wake of two contra-rotating propellers. An ad-hoc mixed hardware and software phase-locking technique is developed in order to analyze the contribution of each propeller to the overall hydrodynamics of the system