When water flows past a solid object like a cylinder, it creates waves on the surface. A Free-surface Waves on Cylinder CFD simulation is a powerful computer tool that helps engineers study this wave-structure interaction. This is very important for building safe bridges, offshore oil platforms, and ships. A Free-surface Waves on Cylinder Fluent simulation lets us see the powerful forces that waves put on these structures. We can also study the complex flow patterns and vortex shedding that happens behind the cylinder. To do this, we use a special method called the Volume of Fluid (VOF) model. This helps us see the exact line between the water and the air. This CFD study is based on the methods in the reference paper, “Viscous flow past a cylinder close to a free surface” [1].

• Reference [1]: Colagrossi, A., et al. “Viscous flow past a cylinder close to a free surface: benchmarks with steady, periodic and metastable responses, solved by meshfree and mesh-based schemes.” Computers & Fluids181 (2019): 345-363.

Figure 1: The case setup for this Free-surface Waves CFD analysis, as shown in the benchmark paper [1].

Simulation Process: Fluent Setup, VOF Multiphase Model and Structured Grid

For this Free-surface Waves Fluent analysis, we first designed a 2D domain with the cylinder placed near the water surface. We then used ANSYS Meshing to create a high-quality, structured grid made of 271,500 quad cells. A structured grid gives very accurate results, especially near the water surface. The most important step in ANSYS Fluent was choosing the correct multiphase model. We used the Volume of Fluid (VOF) model with a sharp interface setting. This is the best way to track the exact position of the free surface between the water and the air. All the settings for the simulation were chosen based on the reference paper to ensure our results are correct.

Figure 2: The structured mesh used for the VOF Model for Free Surface simulation, with fine cells at the water-air interface.

Post-processing: CFD Analysis, Visualizing Wave Deformation and Hydrodynamic Forces

The phase contour provides a clear, professional visual of the water’s surface as it flows around the cylinder. This professional visual shows the exact boundary between water (volume fraction = 1, shown in red) and air (volume fraction = 0, shown in blue). We can clearly see how the water level rises slightly as it approaches the front of the cylinder and then dips down behind it. This deformation of the free surface is a key result. From this interaction, we measured the forces on the cylinder. The simulation calculated a drag force (pushing force) of 0.15 and a lift force (upward force) of 0.78. These numbers are critical for engineers to design structures that can resist the constant push and pull of flowing water.

Figure 3: A professional visual showing the phase distribution from the Free-surface Waves on Cylinder CFD analysis.

The velocity and temperature contours explain the complex flow physics happening under the surface. The velocity streamlines show water moving at speeds from 0.0 up to 1.3 m/s. This professional visual also reveals a repeating pattern of spinning circles, or vortices, forming behind the cylinder. This pattern is known as vortex shedding and it can cause structures to vibrate. The temperature contour, with values from 300 K to 329.1 K, shows that the water heats up slightly where it moves fastest. This is because the friction of the fast-moving water turns some of its motion energy into heat. The most important achievement of this simulation is the successful capture of the complete free-surface phenomenon—the wave shape, the hydrodynamic forces, and the vortex shedding pattern—all in a single, accurate model, which gives engineers a reliable tool to predict and design for complex real-world marine environments.

Figure 5: Professional contours showing velocity streamlines and temperature distribution from the Marine Hydrodynamics Simulation.