This report shows how we used computational fluid dynamics (CFD) to study an axial fan using the sliding mesh method in ANSYS Fluent. Axial fans are very common in cooling systems, ventilation, and many industrial applications. These fans have blades attached to a center hub and push air along the fan axis when they spin. Our transient simulation (which means it changes over time) helps us see how the fan performance changes as it rotates. We used a time-dependent analysis to track the airflow patterns, pressure distribution, and velocity field inside the duct. Our numerical simulation with 720 rpm rotation speed gives important information about pressure rise, flow separation, and how well the fan works in different conditions.

Figure 1- Axial Fan zone schematic

Simulation Process

There are important points that have to be considered in the simulation`s initial steps. Using Sliding Mesh (Mesh Motion) module set a constraint to having two distinct regions. One stands for rotational and the other for stationary. Further, avoiding drastic changes in cell sizes, particularly around interfaces, is essential. As a result, 3330417 tetrahedral cells are produced. Axial fan is working with 720 rpm implemented in a duct. We seek the performance of axial fan over time, revealing a Transient ( unsteady) simulation.

Figure 2- Generated mesh for axial fan inside a duct

Post-processing

The velocity results in Figures 3 reveal the flow acceleration pattern through the system. In the stationary frame view (Figure 2), the flow starts slow (dark blue, 3-7 m/s) at the inlet, stays relatively slow through most of the duct, then speeds up slightly (light blue, 15-23 m/s) after passing the propeller. The streamline visualization in Figure 4 tells the complete story by showing how air actually moves. The streamlines start organized at the inlet (blue lines, 0-17 m/s), then get twisted as they pass through the rotating propeller blades, reaching speeds of 34-51 m/s (green-yellow). What’s really interesting is how the streamlines straighten out after passing through the fan instead of continuing to spin. This means the duct is doing a good job straightening the flow and converting rotational energy into useful forward thrust. The cone-shaped outlet helps the high-speed flow (yellow streamlines) gradually slow down and spread out, which improves overall propulsion efficiency. Without this expanding section, we’d waste a lot of energy as turbulence and swirling motion.

Figure 4: Velocity contour & Streamline visualization showing the flow paths and velocity magnitudes