Within the last 30 years wind tunnels have evolved as an indispensable aid to the practice of civil engineering. A wind tunnel is a tool used in aerodynamic research to study the effects of air moving past solid objects. A wind tunnel consists of a tubular passage with the object under test mounted in the middle. The earliest wind tunnels were invented towards the end of the 19th century, in the early days of aeronautic research, when many attempted to develop successful heavier-than-air flying machines. The wind tunnel was envisioned as a means of reversing the usual paradigm: instead of the air standing still and an object moving at speed through it, the same effect would be obtained if the object stood still and the air moved at speed past it. Wind tunnels are designed for a specific purpose and speed range and there is a wide variety of wind tunnel types and model instrumentation. Applications of wind-tunnel research range from routine testing of airframes to fundamental research on the boundary layer, the slow-moving layer of air adjacent to any wind-exposed body surface. Measurements of air pressure and other characteristics at many points on the model yield information about how the total wind load is distributed. In addition to aircraft and spacecraft, aerodynamic studies in wind tunnels have been highly profitable devices for solving design problems in automobiles, boats, trains, bridges, and building structures. This book is intended to be a valuable addition to students, engineers, scientists, industrialists, consultants and others providing greater insight into wind tunnel designs and their enormous research potential.