Mach number

In fluid dynamics, the Mach number (M or Ma) (/mɑːk/; German: ) is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound.The subsonic speed range is that range of speeds within all of the airflow over an aircraft is less than Mach 1. The critical Mach number (Mcrit) is lowest free stream mach number at which airflow over any part of the aircraft first reaches Mach 1. So the subsonic speed range includes all speeds that are less than Mcrit.The transonic speed range is that range of speeds within which the airflow over different parts of an aircraft is between subsonic and supersonic. So the regime of flight from Mcrit up to Mach 1.3 is called the transonic range.Aircraft designed to fly at supersonic speeds show large differences in their aerodynamic design because of the radical differences in the behaviour of flows above Mach 1. Sharp edges, thin aerofoil-sections, and all-moving tailplane/canards are common. Modern combat aircraft must compromise in order to maintain low-speed handling; 'true' supersonic designs include the F-104 Starfighter, SR-71 Blackbird and BAC/Aérospatiale Concorde. In fluid dynamics, the Mach number (M or Ma) (/mɑːk/; German: ) is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound.