基于两相欧拉模型的回转体微气泡减阻数值研究

Numerical study on micro-bubble drag reduction of axisymmetric bodies based on two-phase Euler model

为了研究回转体的微气泡减阻影响因素,以及回转体形状对减阻的影响,该文基于Open FOAM中两相欧拉模型对两个回转体进行了微气泡减阻数值模拟。考虑了相间作用力与气泡直径的变化,研究了流体速度、通气速率及气泡尺寸等因素对微气泡减阻的影响。数值结果与前人研究得到的结论相一致,验证了模型的可行性。比较了两种不同形状回转体的减阻效果,分析了不同回转体附近气体分布规律及压力云图,探讨了微气泡减阻机理。数值结果表明:相同通气速率下,流体速度较低时,摩擦阻力的减阻率较大;通气速率与回转体边界层附近的气体体积分数对减阻效果有重要影响;微气泡的存在可以增大回转体的压阻力;对于总阻力的减阻效果,存在一个最佳通气速率;一般微气泡直径较小时,减阻率较高;回转体尾部形状可以影响气体体积分数与局部压力分布,进而影响减阻率,尖尾比钝尾更有利于微气泡减阻。

In order to investigate influencing factors to micro-bubble drag reduction of the axisymmetric body,and the influence of body shape on drag reduction,numerical simulations of micro-bubble drag reduction on two axisymmetric bodies have been conducted based on two-phase Euler-Euler model in OpenFOAM.The interfacial forces and the change of bubble diameter have been considered and the influences of factors such as the flow speed,air flow rate and bubble size on micro-bubble drag reduction have been investigated.The numerical results are in agreement with the conclusions by the previous studies and the feasibility of the present model is verified.The effects of micro-bubble drag reduction for two axisymmetric bodies have been compared and the air volume fraction distribution and pressure contour near the bodies have been analyzed.The mechanism of micro-bubble drag reduction has been also discussed.The numerical results show that under the same air flow rate the cases with lower flow speed will obtain greater frictional drag reduction.The air flow rate and air volume fraction within the boundary layer play important roles in micro-bubble drag reduction.The presence of the micro bubbles will increase the pressure drag.For total drag reduction,there is an optimal air flow rate.Drag reduction rates are generally higher when the bubble size is smaller.The shape of the axisymmetric tail body influences the distributions of air volume fraction and local pressure,and then it has effects on drag reduction consequently.The axisymmetric body with thin tail will have more drag reduction effects than the axisymmetric body with blunt tail.