CFD-calculation of a draft tube flow

This paper reports a numerical simulation of the three-dimensional flow field within a draft tube of the sharp-heel type for a Kaplan turbine. Two operational modes are calculated, i.e. on and off-cam on the propeller curve, which is referred to as Case-T and R. The simulations are performed by using the commercial CFD code Fluent 5.4 and predict interacting vortical structures within the flow. This is second paper presented by the authors on the Turbine-99 draft tube flow. The first calculations (see Skåre et al. (1999)), predicted a recirculation zone downstream the rotating hub. The present simulation predicted no recirculation zones downstream the rotating hub. The differences between the works are mainly due to the used radial velocitydistribution at the annular inlet boundary. Further downstream two recirculation zones are predicted for both Case-T and R. One is predicted at the sharp-heel (outer bend), while the largest zone is found at the outlet, i.e. upper right corner.