A Numerical Study of Vortex Structure in the Shear Layer between Swirling Backflow and Axial Main Flow

It is well known that a backflow occurs in the upstream of an impeller at low flow rate. Such backflow often accompanies a vortex structure. It is considered that the vortex structure is caused by the roll-up of the shear layer between the swirling backflow and an axial main flow. In order to verify this, a simple model test was carried out in which the effect of impeller was represented by an axisymmetric swirling backflow. In the present paper, the flow field of the simplified model test is simulated by using the LES to investigate detailed flow pattern. The computed results are compared with experimental results.