渗透双扩散对流的实验研究

Experimental research of penetrative double-diffusive convection

在直径９０ｍｍ，高１００ｍｍ的容器中，研究了均质流层下常孔隙率的多孔介质上方指状流和烟羽的典型形态、形成条件与动力学。各种流态的形成取决于Ｒａｙｌｅｉｇｈ数Ｒａ与“溶质Ｒａｙｌｅｉｇｈ数”Ｒｓ；其临界条件均符合Ｒａ＝ａＲｓ＋ｂ，ａ、ｂ与系统中液体的物性及多孔介质的渗透率有关。这方程式揭示了形成凝固前沿上方烟羽（偏析通道的孪生现象）时诸因素的定量关系，为推导它们的临界判据打下基础。

The typical morphology and formation conditions and kinetics of plume and fingers in fluids above a horizontal porous layer possessing constant permeability have been investigated withheated salt-water and sugar-water systems within a dia. 90 mm × 1 00 mm vessel.Themorphology depends on Rayleigh number Ra and“ salinity Rayleigh number”Rs.The criticalconditions of plume and fingers flow are Ra=ars +b,where a and b depend on physicalproperties of fluids in the system and permeability.This equation reveals the quantumrelationship during plume formation. Based on plume and channel twin morphology,it makespossible to get the critical conditions of channel formation in casting,through determiningconstants a and b by experimental research.