text: In aerodynamics, the Prandtl–Meyer function describes the angle through which a flow turns isentropically from sonic velocity (M=1) to a Mach (M) number greater than 1. The maximum angle through which a sonic (M = 1) flow can be turned around a convex corner is calculated for M = . For an ideal gas, it is expressed as follows,
  where  is the Prandtl–Meyer function,  is the Mach number of the flow and  is the ratio of the specific heat capacities.
  By convention, the constant of integration is selected such that 
  As Mach number varies from 1 to ,  takes values from 0 to , where
  where,  is the absolute value of the angle through which the flow turns,  is the flow Mach number and the suffixes "1" and "2" denote the initial and final conditions respectively.