Jet Ski: 2-Phase Flow

Jet Ski (Two-Phase Flow Study) — ANSYS Fluent CFD Simulation

Description

This project simulates the motion of a jet ski at the interface between water and air, capturing how a floating body disturbs the free surface as it moves. Flow around floating objects — boats, ships, jet skis — is one of the most common two-fluid phenomena around us, and wherever two fluids meet, the interaction and deformation of the interface becomes the central engineering question. Here the goal is to see how the jet ski rides the surface and reshapes the water behind it. Within the Marine Engineering: Beginner CFD Training Package, this project applies free-surface modeling to a fast-moving marine craft, building on the wave case toward the flow around a real floating body.

Methodology

The physics is handled with the Volume of Fluid (VOF) multiphase model, which tracks the sharp water–air interface as it deforms around the moving body — the standard tool for free-surface and open-channel problems where the shape of the surface is itself a key result. The computational domain has an inlet where water enters at a mass flow rate of 50,000 kg/s and a pressure outlet, with the jet ski floating at the interface. The geometry is built in ANSYS Design Modeler and meshed in ANSYS Meshing as an unstructured mesh of roughly 1,748,941 elements — unstructured here to wrap cleanly around the curved hull geometry.

Analysis

Post-processing provides contours of pressure and velocity, velocity vectors, and the water volume fraction. The volume-fraction field captures the free surface clearly and shows how the phases interact around the floating body — the jet ski is pushed by the flow, and a distinct wake sequence forms behind it, with water lifted above the undisturbed surface level. That surface jump is exactly the behavior you'd expect from a jet ski's interaction with the water, recovered directly from the simulation. By the end of this project, you'll be able to set up a VOF water–air free-surface case around a floating body, define mass-flow inflow and pressure-outlet conditions, and read free-surface deformation and wake structure from the volume-fraction and velocity fields.