New turbulence modeling for air/water stratified flow

The prediction of interfacial turbulence characteristics is one of the still challenging of two-phase stratified flow. The evaluation of some important parameters such as interfacial heat transfer coefficient based on turbulence kinetic energy and turbulence dissipation rate in some models, intensifies the importance of turbulence flow correct simulation. High gradient of velocity and turbulence kinetic energy at the interface of two-phase stratified flow leads to a major overestimation or underestimation of flow characteristics without any special treatment. Consideration of a source function of turbulence eddy frequency at the interface is one of the common solution employed in past researches. Although this solution remedies some shortcomings of traditional methods in smooth stratified flow, its application in wavy stratified flow needs the other modifications. The examination of turbulence characteristics near the free surface reveals that, in addition to turbulence eddy frequency, the other source function of turbulence kinetic energy should be considered near the free interface. So, a new source function of turbulence kinetic energy is proposed at the interface based on flow condition. This new method has been employed for Fabre et al. (1987) experiment designed for air/water stratified flow. The results of simulation have a good agreement with experimental data and turbulence characteristic can be captured near the free surface.