Underwater gliders are amazing robot submarines that can explore the ocean for months without needing much power. They don’t have propellers like normal submarines. Instead, they cleverly change how floaty they are and shift their internal weight to move up and down in a smooth, zigzag path. This energy-saving motion is key to their long missions. To design better gliders, engineers use powerful computer tools like Computational Fluid Dynamics (CFD) to study this complex movement. A special technique called Dynamic Mesh CFD is needed because the computer grid must move and change shape to follow the glider as it swims. Our study uses this advanced method to perform an Underwater Glider CFD simulation, making sure our results are accurate by comparing them to a well-known research paper [1].

• Reference [1]: Busquets-Mataix, Javier, et al. “CFD analysis and hydrodynamic improvement on hybrid buoyancy driven underwater glider for extended range capabilities.”

Figure 1: The Autosub, an example of an Autonomous Underwater Vehicle (AUV) similar to the one studied in this Underwater Glider CFD simulation.

Simulation Process: Modeling Glider Motion with Multiphase Flow

To create the Underwater Glider Movement Using Dynamic Mesh Fluent simulation, we first drew the glider’s shape and the surrounding water and air. Because the glider moves near the water’s surface, we needed to model two different fluids (water and air) at the same time. To do this, we used the Volume Of Fluid (VOF) multiphase model in ANSYS Fluent. The most important part of the setup was activating the Dynamic Mesh feature. This tool tells the computer grid to automatically update itself as the glider moves. We used two methods, Smoothing and Remeshing, to make sure the grid stretches and rebuilds itself smoothly without causing any errors during the simulation. This allows us to accurately track the Glider Movement CFD for its entire journey.

Figure 2: The Dynamic Mesh CFD in action, showing the deformed grid that moves and adapts with the Underwater Glider in ANSYS Fluent.

Post-processing: Analyzing Hydrodynamic Flow and Free-Surface Interaction

The simulation results tell a clear story of cause and effect, revealing the glider’s impact on the water and the model’s ability to capture complex physics. The main cause is the glider pushing its way through the water. The direct effect, shown in Figure 3, is the change in water speed around the glider’s body. We can see a bright green-yellow area at the very front nose of the glider, where the water is forced to speed up to about 1.43 m/s as it moves out of the way. As the water flows along the glider’s smooth sides, it slows down again, shown by the light blue colors. A key achievement here is the use of an adaptive mesh. The computer grid has very small, fine triangles close to the glider to capture these details accurately, while using larger triangles farther away to save time. This smart meshing is crucial for an efficient and precise Underwater Glider Fluent analysis.

Figure 3: Velocity contour from the Glider Movement CFD analysis, showing how water flow accelerates around the front of the vehicle.

Figure 4 shows the second part of our story, focusing on the glider’s interaction with the water’s surface. The cause is the glider moving in an environment with both water (red) and air (blue). The amazing effect is that the boundary between them—the free surface—remains perfectly stable and clear, shown by the thin green-yellow line. Even as the glider moves and the dynamic mesh stretches and deforms around it, the simulation correctly handles this complex interaction without any problems. The most important achievement of this Underwater Glider Movement Using Dynamic Mesh CFD simulation is the successful and robust modeling of the free-surface interaction while the body is in motion. This proves our model can accurately predict how the glider behaves when it surfaces for communication or navigation, which is a critical capability for real-world autonomous missions and a major challenge in CFD.

Figure 4: Volume of Fluid (VOF) phase contour illustrating the stable free-surface interaction between water (red) and air (blue) in the Underwater Glider Fluent simulation.