Water Jet Cavitation

Water Jet Considering Cavitation — ANSYS Fluent CFD Simulation

Description

This project presents a CFD simulation of cavitation inside a water jet — a device that produces a thin, ultra-high-speed water stream (often mixed with an abrasive) to cut or clean hard materials. As water accelerates through the jet, the pressure can fall to its vapor pressure, triggering cavitation: the local formation of vapor bubbles within the liquid. Capturing this phenomenon is essential, because cavitation drives erosion, noise, and performance loss in many fluid devices. In this project, you'll model the phase change between water and vapor and study how the vapor region forms and grows. Within the Mass Transfer: Beginner CFD Training Package, this project introduces cavitation as a pressure-driven phase change, extending the mass-transfer methods from temperature-driven boiling and condensation to a phenomenon governed by pressure.

Methodology

The 2D water jet geometry is designed in Design Modeler and meshed with a structured grid of roughly 57,018 elements for the internal nozzle flow. The VOF multiphase model is set up with water and vapor phases using sharp interface modeling and an implicit formulation, and the cavitation mass-transfer mechanism is activated between the two phases with a defined vapor pressure of 3540 Pa. The boundary conditions are a velocity inlet (10 m/s, pure water) and a pressure outlet. Coupled pressure–velocity coupling is chosen with PRESTO! pressure and Compressive volume-fraction discretization for the cavitating flow, and the k-ε RNG turbulence model with standard wall functions is applied.

Analysis

Post-processing produces pressure, velocity, water volume fraction, and vapor volume fraction contours, used to locate where cavitation begins. The results show the pressure falling as the water accelerates through the jet, and where it reaches the vapor pressure, vapor forms — visible in the vapor volume-fraction field as the cavitation region taking shape. From these you can identify exactly where cavitation initiates and how the vapor region grows. Cavitation is a critical concern in pumps, propellers, valves, injectors, and hydraulic machinery, and the VOF + cavitation mass-transfer workflow built here transfers directly to predicting and mitigating cavitation damage across countless fluid systems. By the end of this project, you'll be able to set up a VOF multiphase simulation with the cavitation mass-transfer mechanism, define the vapor pressure that triggers phase change, configure the solver and discretization for cavitating flow, and interpret the pressure and vapor-fraction fields that reveal where cavitation occurs.