- Consider the inviscid, adiabatic flow of air at free stream conditions, M1 = 2, p1 = 1 atm and T1 = 288 K around a sharp expansion corner (θ = 20°) as shown below. The Prandtl-Meyer function, ν, is given as a function of Mach number, M, as Assume air to be calorically perfect with γ = 1.4. The Mach number, M2 downstream of the expansion corner is approximately
Putting the value M1 in given equation, we have ν(M1) = 26.38°
Now, ν(M2) = ν(M1) + 20°
⇒ ν(M2) = 46.38°, which is correspond to M2 = 2.83.
Note: The Mach number downstream of an expansion corner is always higher than upstream Mach number.