Direct numerical simulations of flows with phase change
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چکیده
We present results from direct numerical simulations of two types of technologically important phase change processes: directional solidification of a binary alloy and film boiling. We use a two-dimensional finite-difference/front-tracking method which allows us to accurately follow the evolution of the interface between the phases. The method is general in the sense that discontinuities in material properties between the phases as well as topological changes are easily handled. In the directional solidification problem the fully coupled solute and energy equations for a dilute binary alloy without fluid flow are solved. The effects of latent heat, unequal material properties between liquid and solid and unsteady effects are completely taken into account. We demonstrate the evolution of a cellular interface with rejection of solute ahead of the advancing interface and in the intercellular grooves. The numerical results for the transition from a planar to a cellular interface are in excellent agreement with linear stability theory. The film boiling problem couples the phase change with fluid flow. This requires the solution of the Navier-Stokes and energy equations with interphase mass transfer. We study the growth and dynamics of a vapor layer adjacent to an upward facing, flat, heated surface. Vaporization of the liquid at the liquid-vapor interface continually replenishes the vapor lost due to bubble departure from the interface.
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تاریخ انتشار 2001