A kinetic theory approach to computation of supersonic nozzle flow with water vapor condensation

A compressible vapor when expanded rapidly may undergo a change of state, condensing from the vapor phase If the phase change to the liquid or even the solid phase, does occur, flow properties such as pressure and temperature may be altered appreciably from those occurring in a corresponding condensation-free isentropic expansion, becomes of particular concern in a wind tunnel nozzle where the working section test conditions and measurement process Use of highly dried air and increased This might be affected, stagnation temperature have traditionally been used to eliminate the detrimental effects of condensation on flow distribution in wind tunnels, However, with the associated costs in obtaining highly dried air and the practical limitations of operating at very high stagnation temperatures. it becomes desirable to understand in more detail the condensation phenomena.

A method is presented to calculate the static pressure and temperature distribution for a supersonic nozzle flow when water vapor is mixed with air. The method combines numerically integrable differential equations governing flows with condensation and the kinetic theory of Buckle and Pouring. This theory for the formation of clusters in a condensing vapor is based on molecular rather than thermodynamic considerations.

The theory was numerically modeled by Pouring into two computer codes: equilibrium conditions and nonequilibrium conditions. The equilibrium code establishes the initial values of the kinetic theory's parameters, while the nonequilibrium code calculates the growth and decay rates of clusters of every size from the theory's unimolecular and bimolecular reaction probabilities.

The computer method was applied to four experimental cases work taken from the condensation investigation work of Pouring. The results of calculations indicate that the method can yield excellent results if the relationship describing the internal energy redistribution frequency is correctly chosen.