Agricultural & Food: Hydraulic Jump of Water in Rectangular Channel

Hydraulic Jump of Water in a Rectangular Channel — ANSYS Fluent CFD Simulation

A hydraulic jump is what happens when fast, shallow water abruptly slows down: the flow height rises sharply, velocity drops, and energy is dissipated in a turbulent transition. It's a key phenomenon in open-channel and agricultural water systems — spillways, irrigation canals, and energy-dissipation structures all rely on understanding where and how strongly a jump forms. This project uses ANSYS Fluent to capture that transition and locate exactly where the jump occurs for two different inlet flow rates.

The water–air system is modeled with the VOF (Volume of Fluid) multiphase approach, which tracks the free surface between the flowing water and the surrounding ambient air. The fluid domain is built in Design Modeler, and a structured mesh of 231,646 elements is generated in ANSYS Meshing.

The case is solved as a steady, pressure-based simulation with gravity included (−9.81 m/s² in the Y-direction). Turbulence is modeled with the standard k-ε model using standard wall treatment, and the VOF model runs with implicit volume-fraction formulation and implicit body forces over two Eulerian phases (air and water). Air enters through a pressure inlet at zero gauge pressure, while water enters through a mass flow inlet. The simulation is run for two inlet water flow rates to compare their effect on the jump. Pressure–velocity coupling uses the SIMPLE scheme, with PRESTO! for pressure, second-order upwind for momentum, and Modified HRIC for the volume fraction.

The results show the hydraulic jump forming at different downstream locations depending on flow rate: the jump occurs about 0.9 m downstream for the lower flow rate and about 2.8 m downstream for the higher one — the stronger flow carries its momentum farther before transitioning. By the end of this project, you'll be able to set up a free-surface VOF simulation, configure the appropriate solver and discretization schemes for two-phase open-channel flow, and predict where a hydraulic jump forms as a function of inlet conditions.