Numerical investigations of micro bubble drag reduction effect for container ships

In the course of the most recent decades reduction of ship resistance and saving fuel consumption to accomplish higher speed with reduction of pollutants has been the significant subject for researchers. Micro bubble drag reduction technique is one of the most interesting thoughts in this field owing to its great advantages, such as considerable potential drag reduction, easy operations, environmental friendliness and low costs. In this study a 3-D numerical investigation into frictional drag reduction by air micro bubbles is applied on KRISO container ship model. The objective is to understand the mechanism of resistance reduction through micro bubbles injection under model ship at different Froude numbers, injection rate and of course volume fractions. The numerical simulations are performed using a commercial CFD code solving Reynolds averaged Navier–Stokes (RANS) equations. A large number of simulations has been performed to investigate the effect of injection of micro bubble under ship model hull to estimate the local coefficient of friction values along ship hull model. The results show that at all of the examined Froude’s numbers, frictional resistance reduction attained at different rates and a maximum drag reduction of 27.6% was obtained at 0.282 Froude number with 4.8% air volume fraction.