  Previous works for a liquid suddenly contacting a gas at a supercritical
pressure show the coexistence of both phases and the generation of diffusion
layers on both sides of the liquid-gas interface due to thermodynamic phase
equilibrium. A related numerical study of a laminar mixing layer between the
liquid and gas streams in the near field of the splitter plate suggests that
mass, momentum and thermal diffusion layers evolve in a self-similar manner at
very high pressures. In this paper, the high-pressure, two-phase, laminar
mixing-layer equations are recast in terms of a similarity variable. A liquid
hydrocarbon and gaseous oxygen are considered. Freestream conditions and proper
matching conditions at the liquid-gas interface are applied. To solve the
system of equations, a real-fluid thermodynamic model based on the
Soave-Redlich-Kwong equation of state is selected. A comparison with results
obtained by directly solving the laminar mixing-layer equations shows the
validity of the similarity approach applied to non-ideal two-phase flows. Even
when the gas is hotter than the liquid, condensation can occur at high
pressures while heat conducts into the liquid. Finally, a generalized
correlation is proposed to represent the evolution of the mixing layer
thickness for different problem setups.
