NUMERICAL ANALYSIS OF FLOW THROUGH STILLING BASIN USING CFD MODEL

A performance study of a stilling basin located downstream of 140 m high dam was attempted in the study using numerical simulation. The hydraulic characteristics of the stilling basin of 140-MW Tanahu (Upper Seti) Hydropower Project situated in Tanahu district in Nepal were investigated by numerical simulation using Computational Fluid Dynamics (CFD) modelling. The flow patterns, velocities at various locations with three different elevations: 293.00, 305.00, 309.00 masl and water levels along a main water course in stilling basin were recorded. A comparative study was made in order to evaluate the capability of the computational fluid dynamics on modeling stilling basin flow, by using results obtained from physical modeling and CFD simulation. FLOW-3D that solves Reynolds-averaged Navier-Stokes (RANS) equations, was used to model the numerical model setup. The flow behavior inside the stilling basin was well represented by the numerical model and there was reasonably good agreements in flow characteristics between the physical and numerical models. The deviations in water levels between physical and numerical model were below 1.9 m and that in flow velocities were below 30%.