Experimental and Numerical Investigation of Using Coanda Effect for Producing Underwater Propulsion

In this study, the Coanda effect phenomenon and its advantages to produce underwater propulsion have been evaluated experimentally and numerically. The Coanda effect is the tendency of a jet flow to follow a convex surface. This effect is used to multiply the flow volume rate through a nozzle-diffuser channel. A ring shape jet flow is injected toward the throat, which follows the curved surface along the channel. Surrounding fluid sucked into the nozzle was pushed toward the exit section of the diffuser. The flow is several times more than the jet flow rate therefore it can be used as a propulsion system. A series of experimental Bollard tests were performed to investigate the system behavior with respect to the different size of the gap and the jet flow rate. Also, a numerical model was used for simulating the tests for similar conditions. A good agreement is observed between numerical and experimental results. The numerical tool was then used to predict the amount of thrust where free stream velocity was 2.5m/s. the Comparison of the flow multiplier performance with a regular propeller shows that it is possible to use of the water flow multipliers as underwater propulsion systems with acceptable performance.