Waterjet intake flow improvement using boundary layer blowing and vortex generators

It is known that the boundary layer along the roof of a waterjet intake is likely to separate when the boat is moving at relatively high speed and this impairs the overall performance of the waterjet unit. As the speed of the boat increases the size of the separated region increases as well. This paper shows the results of using experimental methods to reduce the extent of the separated region. Ex-perimental work has been undertaken using windtunnel simulation. Impeller plane flow improve-ment was computed by comparing the stagnation pressure distribution of the intake with design modifications against that of the bare intake. Vortex generators and boundary layer blowing have been successfully used to improve the uniformity of the flow entering the impeller. Experimental results using vortex generators at low and high boat speeds show 15 % and 10 % fractional improve-ment with corresponding values for boundary layer blowing of 61 % and 18%