Numerical Simulation Research Of Bubble Flow Based On The Method Of Volume Force Control

In two-phase flow,gas-liquid flow widely exists in nature and industry.Compared with particle flow,the force law is more complicate because the interface of the bubble is easy to deform.In order to better describe the movement of bubbles around the flow,a volume force control method based on two parameters is proposed in this paper which established the relationship between the control force and the instantaneous displacement of the bubbles,so that the position of the bubbles can be quickly fixed.The numerical examples verify the reliability and efficiency of the numerical method.The volume force control method was used to numerically study the flow around the bubble and the effects of Weber number and Reynlods number on the flow are focused on.Controlling Weber number through changing the surface tension coefficient,and the Reynolds number is controlled by changing the viscosity of the liquid phase.Firstly,the flow of bubbles around small Weber numbers is studied.The results show that stable flow field results can be obtained under unsteady calculations.At a small Weber number,the overall deformation of the bubble is small,and the bubble tends to be squashed,other than that the stretching direction is perpendicular to the incoming flow direction.The degree of bubble deformation depends on the Weber number,but has little relationship with the Reynolds number.Studing the bubble flow around the large Weber number with increasing the Weber number.The results show that the overall deformation of the bubble is severe under large Weber numbers.Stable flow field results can be obtained when the Reynolds number is small.As the Reynolds number rises,the bubble flow field and bubble morphology begin to show unsteady oscillations.The bubbles cannot maintain their complete morphology and break up occurs as the Reynolds number is further increased.In order to have a comprehensive understanding of the bubble morphology,the operating conditions in the range of Weber number between 1-20 and Reynolds number between 1-1000 were studied,based on which the bubble morphology map was given.According to the characteristics of bubble morphology,the map is divided into four intervals,including small Weber number interval,small Reynolds number interval,bubble oscillation interval and bubble breaking interval.The bubble resistance was further studied for bubbles with stable morphology.According to the analysis of the force balance,the bubble resistance is given by the control force.As a general trend,the resistance coefficient decreases with the increase of the Reynolds number,and increases with the rise of the Weber number.But when Reynolds number is small,the resistance coefficient depends only on the Reynolds number,and has little to do with the Weber number.