Abstract:The model of T-junction was simulated based on Fluent hydrodynamics software.The mass flow of air and liquid phases,the distribution regularities of velocity and pressure in T-junction were studied when the inlet flow pattern was annular,especially the uneven distribution of oil and air caused by Coanda effect which had influence on the above regularities of distribution.The results show that when the curvature radiuses of the manifold at connection are different,Coanda effect leads to the uneven distribution of oil-air annular flow.The smaller the curvature is,the greater the air phase mass flow inside the manifold is,and liquid mass flow is smaller.The smaller the curvature of the branch pipe at connection is,on contrary,the smaller of it is.The pressure at the inlet of T-junction connection is high,but the pressure gradient is small.The pressure gradient in the small curvature side of horizontal pipe is larger than that of the large curvature side.