Numerical Simulation of Swirling Flow and Pressure Pulse in Hydroturbine Draft Tube

摘要

This paper deals with the Extension Project of Danjiangkou Hydropower Station. The power station provides favorable primary conditions and a good opportunity of carrying on extension with water-allocating from south to north at the same time, and the extension project can bring about electric consumption benefit after it is completed. The numerical simulation of swirling flow and pressure pulse are studied in this paper. The three-dimensional structure modeling of draft tube is made by the method of oblique section. The flow differential equations in draft tube are formulated and the continuity equation of incompressible flow and Reynolds-averaged Navier-Stokes equations are used to simulate the flow in draft tube. And the complete equations are closed by using the Reynolds stress equations. The control equations in unstructured tetrahedron mesh are dispersed in space by Finite volume method(FVM). In time-dispersed format, the second order implicit schemes are adopted. The SIMPLEC method is used to disperse equations to get the solutions. And the process of changing with pressures and velocities in the draft tube can be captured. The swirling flow (eccentric eddies) and pressure pulse in the draft tube can be calculated. The second order central scheme is used to solve source term and diffusive term in governing equation; and the second order upwind scheme to solve convective term in governing equations. After capturing the unsteady data in draft tube, it is convenient to analyze the characteristics of pressure pulse in draft tube, thus finding The main frequency and corresponding amplitude of pressure pulse.