Twofluid model for twophase flow
Abstract
The twofluid model formulation is discussed in detail. The emphasis of the paper is on the threedimensional formulation and the closure issues. The origin of the interfacial and turbulent transfer terms in the averaged formulation is explained and their original mathematical forms are examined. The interfacial transfer of mass, momentum, and energy is proportional to the interfacial area and driving force. This is not a postulate but a result of the careful examination of the mathematical form of the exact interfacial terms. These two effects are considered separately. Since all the interfacial transfer terms involve the interfacial area concentration, the accurate modeling of the local interfacial area concentration is the first step to be taken for a development of a reliable twofluid model closure relations. The interfacial momentum interaction has been studied in terms of the standarddrag, lift, virtual mass, and Basset forces. Available analytical and semiempirical correlations and closure relations are reviewed and existing shortcomings are pointed out. The other major area of importance is the modeling of turbulent transfer in twophase flow. The twophase flow turbulence problem is coupled with the phase separation problem even in a steadystate fully developed flow. Thus the twophase turbulence cannot be understood without understanding the interfacial drag and lift forces accurately. There are some indications that the mixing length type model may not be sufficient to describe the threedimensional turbulent and flow structures. Although it is a very difficult challenge, the twophase flow turbulence should be investigated both experimentally and analytically with long timescale research.
 Publication:

Presented at the Department of Energy International Workshop on Twophase Flow Fundamentals
 Pub Date:
 June 1987
 Bibcode:
 1987doe..work.....I
 Keywords:

 Fluid Mechanics;
 Interfaces;
 Mathematical Models;
 Turbulent Flow;
 Two Phase Flow;
 Energy Transfer;
 Mass Transfer;
 Momentum Transfer;
 Phase Separation (Materials);
 Steady State;
 Fluid Mechanics and Heat Transfer