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7	2nd YEAR FLUIDS / COMPRESSIBLE FLOW	3
- THE MAIN PARAMETER THAT DETERMINES THE CHARACTER OF COMPRESSIBLE FLOWS IS THE MACH NUMBER, M, DEFINED AS THE RATIO BETWEEN THE FLUID VELOCITY AND THE SPEED OF SOUND. FLOW CLASSIFICATION M < 0.3 THE FLOW CAN BE TREATED AS INCOMPRESSIBLE (TO BE SHOWN LATER) 0.3 < M < 0.8 COMPRESSIBLE SUBSONIC FLOW M = 1 SONIC FLOW 0.8 < M < 1.2 TRANSONIC FLOW 1.2 < M < 3 SUPERSONIC FLOW M > 3 HYPERSONIC FLOW - THE SIGNIFICANCE OF THE MACH NUMBER IN COMPRESSIBLE FLOWS IS SIMILAR TO THAT OF THE FROUDE NUMBER IN OPEN CHANNEL FLOWS.