Effect of Di erent Geometries in Simulation of 3D Viscous Flow in Francis Turbine Runners


1 Department of Mechanical Engineering,Sharif University of Technology

2 Department of Mechanical Engineering,Clarkson University


Abstract. Overall turbine analysis requires large CPU time and computer memory, even in the
present days. As a result, choosing an appropriate computational domain accompanied by a suitable
boundary condition can dramatically reduce the time cost of computations. This work compares di erent
geometries for numerical investigation of the 3D
ow in the runner of a Francis turbine, and presents an
optimum geometry with least computational e ort and desirable numerical accuracy. The numerical results
are validated with a GAMM Francis Turbine runner, which was used as a test case (GAMM workshop on
3D computation of incompressible internal
ows, 1989) in which the geometry and detailed best eciency
measurements were publically accessible. In this simulation, the
ow is assumed to be steady and the inlet
boundary condition is prescribed using experimental data. The e ect of turbulence is considered by the
k ????" model. The present investigation demonstrates that consideration of 2-blade geometry with periodic
boundary conditions is the best choice of computational domain. By 1-blade geometry, convergence of
the numerical simulation is not appropriate, whereas 13-blade geometry leads to a coarse grid that can
increase inaccuracy and computational cost. Finally, this paper presents a qualitative survey to forecast
cavitation region inception which correlates satisfactorily with experimental observations.