Turbulence Behavior below an Gas-Liquid Interface and Effects of Interfacial Waves in a Horizontal Stratified Flow.

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Momentum transfer across an air-water interface was studied in a horizontal stratified flow through experimental and numerical analysis. When the liquid Reynolds number equaled to 1200, the smooth interface behaved similar to a solid wall, while the wavy interface behaved different from a solid wall. When the Reynolds number was 11500, turbulence near the interface was completely different from the wall turbulence. In numerical analysis, the k-epsilon model was modified to satisfy asymptotic behavior of turbulent energy, dissipation rate and Reynolds stress to the interface. The modified k-epsilon model could quantitatively predict the turbulence behavior below the smooth interface.Heat transfer by direct contact condensation at a steam-subcooled water interface was investigated in a horizontal rectangular channel. Three types of models were used to predict the heat transfer coefficients at the interface. The heat conduction model provided the lowest limit of heat transfer. The modified K-epsilon model, which could simulate the near-interface variation of the turbulence quantities, showed the more improved prediction compared with the wall k-epsilon model and agrees with the experimental results with smooth interfaces. The condensation heat transfer with interfacial waves were predicted qualitatively by introducing the interfacial wave effect into the surface renewal model.