A wind tunnel is a wind tunnel laboratory. It is a kind of pipe-like experimental equipment that artificially generates and controls the air flow to simulate the flow of air around the aircraft or the entity, and to measure the effect of the air flow on the entity and observe physical phenomena. , It is one of the most commonly used and effective tools for aerodynamic experiments.

A tunnel is an engineering building buried in the ground, and it is a form of human use of underground space. Tunnels can be divided into traffic tunnels, hydraulic tunnels, municipal tunnels, mine tunnels, and military tunnels.