A Simulation Method of Liquid Column Separation-Bridging Water Hammer Based on 3D CFD

Abstract

The invention discloses a liquid column separation-bridged water hammer simulation method based on three-dimensional CFD (Computational Fluid Dynamics). The liquid column separation-bridged water hammer simulation method comprises the following steps: by carrying out three-dimensional modeling and mesh generation, firstly, carrying out single-phase compressible stable-state calculation of a water body to obtain a stable-state fluid field; then carrying out liquid column separation gas-liquid two-phase transient flowing calculation; and finally, processing a computed result by using post-processing software. According to the liquid column separation-bridged water hammer simulation method, on the basis of simultaneously considering the compressibility of the water body and steam, the mass transfer between gas and liquid is considered, and liquid column separation types do not need to be distinguished, so that a mathematical model and a solving method thereof are simplified to a certain extent and the simulation accuracy is relatively high; and unreal pressure pulse similar with one-dimensional simulation is not formed, and visualization of primary formation, development and collapsing processes of a hollow hole in a liquid column separation process is realized.

Description

technical field [0001] The invention relates to a three-dimensional simulation method when liquid column separation-bridging water hammer gas-liquid two-phase transient flow occurs in a water delivery overcurrent system, and belongs to the technical field of hydraulic numerical simulation of hydropower stations (pump stations). Background technique [0002] In the water delivery overcurrent system, the sudden load shedding of the hydropower unit, the start and stop of the water pump unit, the shutdown of the accident condition, and the sudden action of the regulating valve can all cause rapid changes in flow and pressure. When the pressure drops below the vaporization pressure, the liquid vaporizes to form cavitation bubbles. Cavitation bubbles flow with the liquid, and may even develop and accumulate to occupy the entire cross-section of the flow, breaking the liquid column and causing liquid column separation. When the pressure in the tube rises, the cavity collapses, and...

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Problems solved by technology

The existing one-dimensional model cannot effectively simulate the shape and position of the cavity during the liquid column separation process

In particular, the liquid column separation phenomenon in the draft tube of the hydropower station and the pumped storage power station will have a more complicated hydraulic transition process, and the inlet water flow has a peripheral velocity component. Due to the centrifugal force, there must be a rotating vortex in the draft tube. zone, while the center pressure of the vortex zone is the lowest, and the one-dimensional model is difficult to simulate at this time

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