Numerical investigation of microbubble drag reduction on an axisymmetric body based on Eulerian multiphase model

This study employs numerical simulation to investigate the microbubble drag reduction on an axisymmetric body underwater vehicle. The Eulerian multiphase model and the k-omega turbulence model are utilized to simulate gasliquid two-phase flow. The results show that air injection reduces the frictional drag of the vehicle but increases the pressure drag. The reduction in frictional drag is directly related to the surface air volume fraction. Due to the buoyancy effect, the distribution of bubbles around the vehicle is non-uniform, especially at lower water velocities. After air injection, lower velocity or even flow separation is observed near the tail of the vehicle. The flow separation results in localized energy losses and reduces pressure there, ultimately increasing the pressure drag. The flow separation and pressure drop near the top of the tail section are more severe than near the bottom. Flow separation near the tail is more likely to occur with higher air flow rates and lower water velocities. Considering solely the impact of bubble diameter, smaller bubbles tend to adhere closer to the surface of the vehicle, resulting in a greater reduction in frictional drag but also leading to higher pressure drag.