When objects move through air, forces are generated by the relative motion between air and surfaces of the body, study of these forces generated by air is called aerodynamics. Based on the flow environment it can be classified in to external aerodynamics and internal aerodynamics; external aerodynamics is the flow around solid objects of various shapes, where as internal aerodynamics is the flow through passages in solid objects, for e.g. the flow through jet engine air conditioning pipe etc. The behavior of air flow changes depends on the ratio of the flow to the speed of sound. This ratio is called Mach number, based on this mach number the aerodynamic problems can be classified as subsonic if the speed of flow is less than that of sound, transonic if speeds both below and above speed of sound are present, supersonic if characteristics of flow is greater than that of sound and hypersonic if flow is very much greater than that of sound. Aerodynamics have wide range of applications mainly in aerospace engineering ,then in the design of automobiles, prediction of forces and moments in ships and sails, in the field of civil engineering as in the design of bridges and other buildings, where they help to calculate wind loads in design of large buildings.