ABSTRACT
Wind tunnels are devices which provide air streams flowing under controlled conditions so that models of interest can be tested using them. Low-speed tunnels are those with test-section speed less than 650 kmph. Depending upon the test-section size they are referred to as small size or full scale tunnels. Tunnels with test-section speed more than 650 kmph are called high-speed tunnels. The predominant aspect in high-speed tunnel operation is that the influence of compressibility is significant. The wind tunnel fan, looking similar to the propeller of an airplane, operates under peculiar conditions that put it in a class by itself. Wind tunnels have honeycombs in the settling chamber, in order to improve the flow quality in the test-section. High-speed tunnels are those with test-section speed more than 650 kmph. One possible coordinate system is fixed to the wind tunnel-the wind axis system- and is aligned to the main flow direction.
