Numerical Simulation Of Axisymmetric Body’s Drag Reduction And Noise By Micro Bubbles

Because of the energy crisis, ships which is good at energy saving and environmentprotecting are catching more and more researchers’ attention. Injecting micro bubbles intoturbulent boundary is a effective way to save energy and protect environment. This paperis to calculate the effect of injecting micro bubbles into turbulence boundary of anaxisymmetric body in reducing drag and flow noise. The injecting of micro bubbles intoturbulence boundary has changed the structure of turbulence, having a great effect on thefriction drag and pressure drag. The changes of the turbulence structure also have changedthe distribution and power of the pressure on the axisymmetric body. This paper hascalculated the effect of the micro bubbles to the drag of the axisymmetric body in thedifferent injecting velocity, injecting angle, relative velocity ratio and diameters of themicro bubbles. This paper used the mixture model as the multiphase model and k RNG model as the turbulent model. Two kinds of axisymmetric body are used as thesimulation models. The simulation results indicate that the friction drag reduction rate risewith the increase of the velocity. When the micro bubbles is in saturation, the friction dragreduction rate have little change. In the high water velocity, because the ratio of thefriction drag in the total drag is small, the micro bubbles have increased the pressure dragso that the total drag increases. In the simulation, three different diameters of microbubbles is injected into the boundary of the turbulence. The two different diameters is0.001mm and0.01mm. The results show that the diameter has little effect on the darg. Inthe different injecting angles of the micro bubbles, when the injecting angle is vertical tothe income flow, the effect of drag reduction is better than others. This paper has used theFW-H acoustic model calculating the flow noise and radiated noise of the axisymmetricbodies. The injecting of micro bubbles into the boundary leads the flow noise higher andthe radiated noise lower.