An Axial Fan CFD analysis helps us understand how fans work. Axial fans are everywhere. We find them in computers, air conditioners, and big industrial machines. Their job is to move air. The fan has blades that spin around a center part. When they spin, they push air in a straight line, along the same direction as the center part. In many cases, just knowing the average performance of a fan is not enough. We need to see how the airflow changes at every moment as the blades spin. This is especially true when we want to study problems like noise or vibrations.

To see these changes over time, we need a special kind of simulation. This report shows an Axial Fan Transient Fluent simulation. “Transient” means the simulation changes with time. We use a powerful method called Axial Fan Sliding Mesh CFD. This method lets us watch the airflow patterns, the pressure, and the speed of the air as the fan blades are actually rotating. This gives us a very real and detailed movie of the fan at work, which is much better than a single snapshot. By studying this movie, we can see exactly how the fan adds energy to the air and find ways to make it work better.

Figure 1- Axial Fan zone schematic

Simulation Process: The Sliding Mesh Technique

To model the fan correctly, we used a 3D model of the fan inside a duct. The key to this Axial Fan Transient CFD study is the Sliding Mesh method. This method is perfect for things that spin. We split our model into two main parts, as shown in Figure 1.

1. A Spinning Part: We created a cylinder-shaped zone of mesh right around the fan blades. In the simulation, we tell ANSYS Fluent to make this whole zone spin at 720 revolutions per minute (rpm), just like the real fan.
2. A Still Part: The rest of the duct, which does not move, is the second part.

The simulation then lets the spinning part “slide” past the still part. At every small step in time, Fluent calculates the airflow in both zones and shares the information across the boundary between them. This lets us see the true, unsteady effects of the spinning blades on the air. We used a fine mesh with over 3.3 million cells, with many small cells near the blades (Figure 2), to capture all the important details of the flow.

Figure 2- Generated mesh for axial fan inside a duct

Post-processing: CFD Analysis, How Spinning Blades Create Pressure and a Swirling Jet

The simulation results give us a very clear and detailed story about how the fan works. The main cause of everything is the spinning of the fan blades. The direct effect of the blades pushing the air is a large change in pressure. The pressure contour in Figure 3 is the perfect proof. On the front side of the blades, where the air is sucked in, we see a large area of low pressure (shown in blue, around -250 Pa). On the back side of the blades, where the air is pushed out, the pressure is much higher (shown in green and yellow). This pressure difference between the front and back of the blades is what creates the force that pushes the air through the duct. This is the fan’s main job, and the simulation shows it is working correctly.

Figure 3: Pressure contour plot. This image clearly shows the low-pressure zone (blue) on the suction side and the higher-pressure zone on the discharge side of the fan blades.

Figure 4: Velocity streamlines. This image shows the path of the air. The lines show how the air is straight at the inlet, gets twisted into a swirl by the fan, and then starts to straighten out again toward the outlet.

This pressure difference is the cause of the next important effect: it creates a fast-moving jet of air. But because the blades are spinning, they don’t just push the air straight. They also make the air jet spin, like a corkscrew. This spinning motion is called “swirl.” The streamlines in Figure 4 are the best proof of this. We can see the lines, which show the path of the air, are straight before they reach the fan. Then, as they pass through the blades, they speed up (change color to yellow) and get twisted into a spiral shape. This swirl is a natural result of the fan’s rotation. However, swirl is often wasted energy. An interesting effect we see in Figure 4 is that as the air moves away from the fan, the streamlines start to straighten out again. This is very good because it means the fan system is turning the wasted spinning energy back into useful, straight-moving airflow. The most significant achievement of this Axial Fan Sliding Mesh CFD analysis is that it successfully captures the true, time-changing behavior of the fan. It shows clearly how the blade rotation (the cause) creates both a pressure difference and a high-speed, swirling jet of air (the effect). By seeing exactly how the air swirls and then straightens out, engineers get vital information to design quieter fans, reduce energy waste, and build more powerful and efficient ventilation and cooling systems.