Flow swirl is generally unsteady, b

Flow swirl is generally unsteady, both in direction of rotation and speed of rotation. The CFD results in all the cases are examined for flow quality approaching the pump suction. The swirl angle was calculated from the tangential velocity divided by the area-averaged axial velocity calculated at the plane just before flow before entering pump propeller.As per ANSI/HI pump standards the swirl angle must be less than 5 degrees, maximum short-term up to 7 degrees may be acceptable. Following table shows, average and local maximum swirl angel in short-term simulation results is above the limit based on the calculation.