Can you explain how the blades of a fan create a flow of air, and why this flow causes air to be drawn in towards the fan?
Sure, I'd be happy to explain!

The blades of a fan create a flow of air by using their curved shape to move air from one location to another. As the fan blades rotate, they push air in front of them and create regions of high pressure. Meanwhile, on the other side of the blades, a region of low pressure is created. This pressure differential between the two sides of the fan blades causes air to flow from the high-pressure region to the low-pressure region, resulting in a stream of air being blown out from the fan.

The movement of air created by the fan also causes surrounding air to be drawn in towards the fan, a phenomenon known as entrainment. This happens because the flow of air created by the fan causes a drop in pressure in the surrounding area, which leads to air being drawn towards the fan. The direction and strength of this entrainment will depend on the design of the fan and the surrounding environment.

It's worth noting that the efficiency of a fan can be impacted by factors such as the design of the blades, the speed at which they rotate, and the shape and size of the fan housing. In addition, factors such as the density and viscosity of the air can also affect the performance of a fan.