This book presents current research in the study of wind tunnels, including the design, execution and numerical rebuilding of a plasma wind tunnel with the aim to analyse shock wave boundary layer interaction phenomena; the Mainz vertical wind tunnel facility experimenting on cloud physics and chemistry; an air-conditioned wind tunnel environment for the study of mass and heat flux; using wind tunnel studies to evaluate the drag coefficient of the tree crown and Pre-X aerodynamic/aerothermal characterisation through computational fluid dynamics and wind tunnels.