Study of the cavitating instability on a grooved Venturi profile

TL;DR

This study investigates how grooved surface textures on a Venturi profile can passively control cavitation, reducing or eliminating destructive cloud cavitation by altering cavity dynamics.

Contribution

It introduces a passive cavitation control method using organized grooves on a Venturi surface, showing how groove geometry influences cavity behavior.

Findings

Grooves reduce the length of the sheet cavity.

Grooves can suppress cloud cavitation shedding.

Groove depth significantly affects cavity dynamics.

Abstract

Cavitation is a limiting phenomenon in many domains of fluid mechanics. Instabilities of a partial cavity developed on an hydrofoil, a converging-diverging step or in an inter-blade channel in turbomachinery, have already been investigated and described in many previous works. The aim of this study is to evaluate a passive control method of the sheet cavity. According to operating conditions, cavitation can be described by two different regimes: an unstable regime with a cloud cavitation shedding and a stable regime with only a pulsating sheet cavity. Avoiding cloud cavitation can limit structure damages since a pulsating sheet cavity is less agressive. The surface condition of a converging-diverging step, like a Venturi-type obstacle, is here studied as a solution for a passive control of the cavitation. This study discusses the effect of an organized roughness, in the shape of longitudinal grooves, on the developed sheet cavity. Analyzes conducted with Laser Doppler Velocimetry, visualisations and pressure measurements show that the grooves geometry, and especially the groove depth, acts on the sheet cavity dynamics. Results show that modifying the surface condition, by varying the grooves geometry, can reduce cavity sheet length and even suppress the cloud cavitation shedding.