Blockage effect influence on model-scale marine propeller performance and cavitation pattern

The blockage effect is one of the drawbacks in the use of cavitation tunnels, which may considerably interfere in the measurements of the hydrodynamics of model-scale propellers. The literature presents some methods to correct the acquired values, such as the Glauert method, but the deduction of this method does not consider the cavitation effects. This paper aims to use CFD tools to compare and analyze the effect of different levels of blockages on the thrust, torque, hydrodynamic efficiency, and cavitation on two model-scale marine propellers. Five different blockage ratios (from 1% to 41%) and three test cases are simulated, varying the advance ratio to compose the propeller performance diagram. The simulations have shown that the Glauert formula satisfactorily corrected thrust, torque, and hydrodynamic efficiency, even in moderate cavitation. When cavitation is intense, it is observed that the blockage decreases the thrust and torque, not being recommended to use the Glauert formula. It is observed that the cavitation is sensitive to blockage, and it can affect its pattern on the blade surface.