Open Channel Flow: Jet Ski

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.

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.

Setup: 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. Geometry is built in ANSYS Design Modeler and meshed in ANSYS Meshing as an unstructured mesh (~1,748,941 elements) — unstructured here to wrap cleanly around the curved hull geometry.

What the results show: contours of pressure, velocity, velocity vectors, and 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.

You'll learn 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 volume-fraction and velocity fields.