Numerical study on the flow in balancing hole

In order to investigate the value of discharge coefficient of balancing hole Cd for wide range of axial flow velocity v in the hole and rotational speed u, series of CFD simulations are made. Some of the result agrees well with the existing experimental data, but the difference is about 20% in some cases with high Rev. Also, for wide area of Rev, the effect of rotating speed u becomes significant. So it is considered that the parameter v/u is a dominant indicator of Cd . Furthermore, for very low range of v/u, we found a rare flow situation with S-shaped streamlines. In this flow, pumping of disk is so strong and Cd may differ largely.