壁面效应对剪切稀化流体内气泡上浮特性的影响

数值研究了壁面效应对剪切稀化流体内气泡上浮运动特性的影响,气液两相的界面捕捉采用流体体积(VOF)法,剪切稀化流体流变特性和气液相间表面张力的计算分别采用Carreau模型和连续表面张力模型.详细研究了不同流变指数下,壁面效应对气泡形状、液相流场和气泡终端速度的影响.结果表明,强的壁面效应或弱的剪切稀化程度会限制气泡的变形和尾涡的形成,使气泡的终端速度减小;气泡终端速度最易受壁面效应的影响;强的壁面效应和强的剪切稀化程度会导致高剪切速率区域出现在壁面附近,引起壁面附近液相表观黏度大幅度的下降.

Wall Effects on Floating Characteristics of Bubbles in Shear-Thinning Fluids

The wall effects on the floating motion of bubbles in shear?thinning fluids were in?vestigated with the numerical method.The interface between the bubble and the liquid phase was tracked with the volume of fluid(VOF)method.The Carreau model and the continuous surface tension model were used to calculate the rheological properties of the shear?thinning fluid and to compute the surface tension between gas and liquid phases,respectively.For differ?ent rheological indexes,the wall effects on the bubble shape,the liquid?phase flow field and the bubble terminal velocity were studied in detail.The results show that,the strong wall effect or the weak shear?shining effect can hinder the bubble deformation and the formation of wake vortices,and can reduce the bubble terminal velocity.Among all physical parameters,the bub?ble terminal velocity is most liable to the wall effect.For the strong wall effect and the strong shear?shining effect,the high?shear?rate region will occur near the wall,which results in a sig?nificant decrease in the apparent viscosity of the liquid phase near the wall.