Conference on Modelling Fluid Flow (CMFF’09) The 14 th International Conference on Fluid Flow Technologies Budapest, Hungary, September 9-12, 2009 NUMERICAL STUDY OF THE INFLUENCE OF GEOMETRICAL P ARAMETERS ON FLOW IN W ATER PUMP-SUMP Abir ISSA 1 , Annie-Claude BAYEUL-LAINẺ 2 , Gérard BOIS 3 1 Arts et Metiers PARISTECH, LML, UMR CNRS 8107, 8 Boulevard Louis XIV 59046 Lille Cédex, France Fax: +33 20 53 55 93. E-mail: issa@etudiants.ensam.fr 2 Arts et Metiers PARISTECH, LML, E-mail: annie-claude.bayeul@ensam.eu 3 Arts et Metiers PARISTECH, LML, E-mail: gerard.bois@ensam.eu ABSTRACT Water for irrigation, domestic and industrial supply as well for some power generation is normally drawn directly from rivers or from reservoir through sumps. The flow at the pump section sump may have large effects on the pump performances and the operating conditions. The flow patterns in the sump are mainly determined by the shape and scale of the sump. However, it’s not always possible to design a sump pump to provide uniform and stable flow to pumps, due to site constraints. For example in some cases air entraining (surface and subsurface vortex) occurs. These vortices may reduce pump performances and lead to increase plant operating costs. It becomes essential to investigate the pump sump to avoid these non uniformities inlet flow problems. Two approaches (experimental and numerical) are generally followed for such investigation. The numerical approach usually used solves the Reynolds averaged Navier-Stokes (RANS) equations with a near-wall turbulence model. In the validation of this numerical model, emphasis was placed on the prediction of the number, the location, the size and the strength of the various types of vortices. In a Previous study [1] some authors have shown the influence on a single type of mesh with different cell numbers, different intake pipe depths and different water levels, for two turbulence models closure. The present paper mainly focuses, first, on the effect of pump intake location in the sump and secondly on the effect of several inlet velocity gradients at inlet sump section. Keywords: air entraining vortex, CFD, free surface vortex, numerical simulation, turbulent model, submerged vortex. NOMENCLATURE C [m] clearance distance from floor D [m] pipe intake diameter g [m/s 2 ] acceleration due to gravity H [m] water level in the sump-pump L [m] the Pump-sump length S [m] submergence depth for the pipe U [m/s] mean velocity in the sump V [m/s] mean velocity in the intake pipe W [m] pump-sump width ν [m 2 /s] kinematic viscosity ρ [kg/m 3 ] water density. σ [n/m 2 ] coefficient of surface tension Fr Froude number for the pipe submergence S k turbulent kinetic energy Re Reynolds number in the pipe ω rate of turbulent energy dissipation 1. INTRODUCTION It’s essential to design a sump pump provide fairly uniform and free vortices flow to the pumps. However, it’s not always possible, due to geometrical site specific constraints, which may cause a poor design of the intake. Low intake submerges depth could also results in the formation of the air entraining free surface vortices that could as well promote cavitation, [2]. Non uniform inlet flow field at sump entrance even far from pump intake section can also leads to accumulative effects due to 3D boundary layers development on the side-wall creating corners vortices that can be strength by local strong streamline curvature when approaching pump intake. All these non uniformities may cause flow instabilities, vibration and other undesirable phenomena that can cause operating difficulties and frequent maintenance of the whole pump arrangements. Melville et al. [2] have listed the main geometrical parameters could influence the flow