Abstract

The vortex shedding phenomenon of the three-way pipe is the main excitation source for pipe vibration, which can lead to the acoustic resonance. In this paper, the vortex shedding phenomenon under the water medium of the three-way closed branch pipe is studied. The test device of a three-way branch pipe with one branch closed is established to verify the mechanism. The PIV measurement method is used to obtain the change characteristics of the flow streamline and velocity distribution of the closed branch pipe under different working conditions. Tests have shown that due to the special structure of the three-way branch pipe with one branch closed, pressure waves are formed at the location of the three-way and vortices are formed in the branch pipe. A large velocity gradient will be generated when the fluid flows through the junction area of the main pipe and the branch pipe. The small vortex clusters that continuously fall off are formed at the front edge of branch pipe that; due to the fluid viscosity, the fluid at the front edge of the branch pipe will be driven downstream by the mainstream area, creating a vacuum area at the front edge. At the interface between the main pipe and the branch pipe, the velocity fluctuation of the vortex increases with the increase of the flow velocity., The size of the vortex cluster in the branch pipe increases with the increase of the velocity and the vortex shedding speed at the front edge of the branch pipe increases with the increase of the velocity.

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