CFD Simulation of the Wakejet flow

Abstract

TheWakejet is a wakeboard with an electrical powered waterjet unit. It is developed by the Swedish company Radinn AB in Malmö. The company aims to develop an updated series of the Wakejet and would like to analyse the flow both inside the waterjet and around the board, as no previous simulations have been conducted. The objective for this thesis is to analyse the Wakejet using the commercial CFDsoftware STAR-CCM+ and try to find areas where improvements can be done. The simulations are performed on the entire Wakejet using free surface simulations as well as on a simplified model of the waterjet unit only. To validate the simplified set-up a validation study is performed on the AxWJ-2 waterjet pump from John Hopkins University where data from physical experiments are available. Calculations made on the simplified waterjet pump model show that the Wakejet’s waterjet pump has a maximum efficiency of 63% at a board speed of 15 knots. On the maximum speed, 25 knots, the efficiency is found to be as low as 25%. The waterjet experiences high amounts of tip leakage blockage at low speeds. Moreover, the design of the stator should be reconsidered since large amounts of separation is found on the pressure side of the blades. Simulation results from the Wakejet model also show that the shape of the intake channel causes a non-uniformity of the inflow to the impeller which should be addressed. On the bright side, the intake grills do not seem to affect the impeller inflow significantly.