Large Eddy & Interface Simulation (LEIS) of disturbance waves and heat transfer in annular flows

A numerical method for forced convective boiling in an annulus needs to be developed in order to elucidate the reason for nucleation enhancement by disturbance waves. We first developed a numerical strategy to model the development of disturbance waves in annular flows where the highly turbulent gas core flow drives the laminar liquid flow upwards using advanced CFD tool TransAT. In which, the interface tracking method (e.g. Level-set) combined with a scale-resolving turbulence simulation technique (Large Eddy Simulation) was employed to capture dominant turbulence and interfacial scales. Then, the disturbance wave phenomenon in a vertical steam-water annulus system was investigated and analyzed. The finding reported in the present work provides insight into the evolution of disturbance wave and its influence on the heat transfer in annular flow. The modeling results revealed that locally hot 'spots' occurred upstream of disturbance wave. These locally overheated zones could play key roles in activating the nucleation boiling sites. In addition, the inception criteria of disturbance wave were explored by adjusting the mass flux of saturated water. And it was found no disturbance waves occurred at liquid film Reynolds number lower than the critical value, 225.