Solution
= Solution
Mass, <momentum>, energy and $c^2=\gamma p/\rho$ eliminate the density and <pressure> ratios. The result is
$$
M_2^2=\frac{2+(\gamma-1)M_1^2}{2\gamma M_1^2-(\gamma-1)},
$$
so a supersonic upstream flow becomes subsonic.
= Solution
Mass, <momentum>, energy and $c^2=\gamma p/\rho$ eliminate the density and <pressure> ratios. The result is
$$
M_2^2=\frac{2+(\gamma-1)M_1^2}{2\gamma M_1^2-(\gamma-1)},
$$
so a supersonic upstream flow becomes subsonic.