Application of J-Groove to the suppression of swirl flow in the draft tube of a Francis hydro turbine

The purpose of this study is to examine the validity of J-Groove in controlling and suppressing the swirl flow in a draft tube of Francis hydro turbine which may cause draft surge. 'J-Groove' composed of shallow grooves and mounted parallel to the pressure gradient on the draft tube wall is a very simple passive device to suppress several abnormal phenomena in turbomachinery. The CFD analysis has been performed using the draft tube of a Francis hydro turbine model. The calculated results of velocity distribution in the draft tube show that a considerable reduction of swirl velocity is attained by using J-Groove. Besides the vortex core around the dead water region near the draft inlet is reduced by J-Groove.