The mixing of two gas flows moving in coaxial pipes separated by a perforated wall

The mixing of two gases possessing different physical and thermodynamic properties in coaxial cylindrical pipes separated by a perforated wall is considered in a one-dimensional scheme. Mass transfer caused by the difference in static pressures in the flows takes place between the media. It is assumed that the gases in the pipe are mixed instantaneously and that thermodynamic equilibrium is established in the mixture of gases. It is also assumed that friction and heat transfer on the walls of the pipes are negligibly small as compared with the mixing effect. When setting up the momentum equation for the motion in the pipe where mixing occurs, the mutual direction of the mixing flows and the angle of incidence of the stream are taken into consideration.