STABILITY OF 2-PHASE STRATIFIED FLOW AS CONTROLLED BY LAMINAR TURBULENT TRANSITION

Flow pattern transition from stratified-smooth to stratified-wavy has been usually identified with a condition of neutral stability, where destabilizing effects are due to the inertia of the two-phases. It is shown that this is indeed the case when instability is approached with laminar gas phase. However, when the upper gas phase is turbulent, a destabilizing term appears due to dynamic interaction of the turbulent flow with the perturbed free interface. At the transitional range from laminar to turbulent flow regime the evolution of wavy pattern is not predicted by stability condition and coincides with the laminar/turbulent flow regime transition.