Two-phase flow pattern transition across micropillars: Size scale effect at the microscale

Size scale effect of adiabatic two-phase cross-flow over micropillars was experimentally investigated, and the mechanisms controlling the formation and transition of the recently discovered bridge flow was examined. A transition criterion, based on the Weber and Euler numbers, for the breakage of the bridges, is provided. The bridges break from the surface when the product of the Weber and Euler numbers is larger than similar to 1; otherwise, the bridges cease to exist by coalescing with liquid slugs. (C) 2008 American Institute of Physics.