A wind tunnel is a device used to test objects' aerodynamic properties, such as aircraft or automobiles, by producing a controlled stream of air over the thing. Wind tunnels are typically large, enclosed structures with a powerful fan or compressor, creating high-speed airflow.
Indoor skydiving, on the other hand, is a recreational activity that simulates the experience of skydiving by using a vertical wind tunnel. Indoor skydiving tunnels are typically smaller and less potent than wind tunnels. They are designed to create a column of air strong enough to support a person's body weight, allowing them to float and move around in the air.
So, the main difference between wind tunnels and indoor skydiving tunnels is their purpose: wind tunnels are used for scientific testing of aerodynamic properties, while indoor skydiving tunnels are for recreational activities. Wind tunnels are typically larger and more powerful than indoor skydiving tunnels explicitly designed for human use.