Unit I Definition / Application of Wind Tunnel

Definition of a Wind Tunnel

A wind tunnel is a specially designed and protected space into which air is drawn, or blown, by mechanical means in order to achieve a specified speed and predetermined flow pattern at a given instant. The flow so achieved can be observed from outside the wind tunnel through transparent windows that enclose the test section and flow characteristics are measurable using specialized instruments. An object, such as a model, or some full-scale engineering structure, typically a vehicle, or part of it, can be immersed into the established flow, thereby disturbing it. The objectives of the immersion include being able to simulate,visualize, observe, and/or measure how the flow around the immersed object affects the immersed object.

Application of Wind Tunnel

There are many uses of wind tunnels. They vary from ordinary to special: these include uses for Subsonic, supersonic and hypersonic studies of flight; for propulsion and icing research; for the testing of models and full-scale structures, etc. Some common uses are presented below. Wind tunnels are used for the following:

(i) To determine aerodynamic loads

Wind tunnels are used to determine aerodynamic loads on the immersed structure. The loads could be static forces and moments or dynamic forces and moments. Examples are forces and moments on airplane wings, airfoils, and tall buildings. 

In our Aerodynamics lab we use load cells to calculate the drag and lift acting on the aerofoil, cylinder, and other models ....(Do you remember in Aerodynamics Lab?)

(ii) To study how to improve energy consumption by automobiles

They can also be used on automobiles to measure drag forces with a view to reducing the power required to move the vehicle on roads and highways.

(iii) To study flow patterns

To understand and visualize flow patterns near, and around, engineering structures. For example, how the wind affects flow around tall structures such as sky scrapers, factory chimneys, bridges, fences, groups of buildings, etc. How exhaust gases ejected by factories, laboratories, and hospitals get dispersed in their environments.

(iv) Other uses include

To teach applied fluid mechanics, demonstrate how mathematical models compare to experimental results, demonstrate flow patterns, and learn and practice the use of instruments in measuring flow characteristics such as velocity, pressures, and torques.