Pressure Calculation for Two-Dimensional Flow Inside Hydraulic Structures

摘要

When static pressure inside a hydraulic structure falls below some critical value, voids containing water vapor form therein. The voids then collapse with great force, pitting and eroding the internal surfaces of the structure. The formation/collapse of these voids is called cavitation, and the prevention thereof is a prime concern in structural design. The VORTEX code has been used to calculate pressure distributions for three distinct flow conditions in the outlet works for Taylorsville Lake, Salt River, KY. A method has been developed for computing the two-dimensional pressure distributions inside hydraulic structures. Velocities are first obtained by finite difference solution of the Navier-Stokes equations in stream-function/vorticity form. Pressure is then calculated by numerical integration of the momentum equation. The method has been incorporated for arbitrary geometry in the VORTEX computer code, which uses boundary-fitted grids generated by the WESCOR code. Computed results compare well with piezometric data from physical-model tests for the Taylorsville outlet works, indicating that the VORTEX code may be useful in identifying and eliminating flow conditions that promote cavitation. Keywords: Internal flow; Pressure calculation; Cavitation.