Smoothing the conservative variables for gases

For gases the conservative variables are smoothed on basis of the local pressure gradient. This gradient is calculated in subroutine presgradient. Subsequently, the smoothing is done in routine smoothshock.f. Next, the velocity boundary conditions are applied in the form \overline{\rho}_{i+1} \boldsymbol{v}_{i+1} to \overline{\boldsymbol{V}}_{i+1}, after which the static temperature, pressure and velocity is determined in routine updatecfd on basis of the smoothed conservative variables. Next, the pressure boundary conditions are applied. At the point the smoothing diversion for gases finishes and liquids and gases are treated again in the same way.