Mass Transfer: Cavitation in a Water Jet

What You'll Build

This lesson walks you through 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.

What You'll Learn

• What cavitation is, why it occurs when pressure drops to vapor pressure, and why it matters in engineering

• How to design a 2-D water jet geometry in Design Modeler

• How to generate a structured mesh (~57,018 elements) for an internal nozzle flow

• How to set up the VOF multiphase model with water and vapor phases using sharp interface modeling and implicit formulation

• How to activate the cavitation mass-transfer mechanism between the two phases, with a defined vapor pressure of 3540 Pa

• How to apply boundary conditions: velocity inlet (10 m/s, pure water) and pressure outlet

• How to choose Coupled pressure–velocity coupling with PRESTO! pressure and Compressive volume-fraction discretization for cavitating flow

• How to apply the k-ε RNG turbulence model with standard wall functions

• How to post-process pressure, velocity, water volume fraction, and vapor volume fraction contours to locate where cavitation begins

Why It Matters

Cavitation is a critical concern in pumps, propellers, valves, injectors, and hydraulic machinery. The VOF + cavitation mass-transfer workflow you build here transfers directly to predicting and mitigating cavitation damage across countless fluid systems.