Basics of Fluid Mechanics, 2014a

CHAPTER 13
Multi–Phase Flow
13.1 Introduction
Traditionally, the topic of multi–phase flow is ignored in an introductory class on fluid
mechanics. For many engineers, this class will be the only opportunity to be exposed
to this topic. The knowledge in this topic without any doubts, is required for many
engineering problems. Calculations of many kinds of flow deals with more than one
phase or material flow 1 . The author believes that the trends and effects of multiphase
flow could and should be introduced and considered by engineers. In the past, books
on multiphase flow were written more as a literature review or heavy on the mathematics.
It is recognized that multiphase flow is still evolving. In fact, there is not a
consensus to the exact map of many flow regimes. This book attempts to describe
these issues as a fundamentals of physical aspects and less as a literature review. This
chapter provides information that is more or less in consensus 2 . Additionally, the nature
of multiphase flow requires solving many equations. Thus, in many books the representations
is by writing the whole set governing equations. Here, it is believed that the
interactions/calculations requires a full year class and hence, only the trends and simple
calculations are described.
13.2 History
The study of multi–phase flow started for practical purposes after World War II. Initially
the models were using simple assumptions. For simple models,there are two possibilities
(1) the fluids/materials are flowing in well homogeneous mixed (where the main problem
1 An example, there was a Ph.D. working for the government who analyzed filing cavity with liquid
metal (aluminum), who did not consider the flow as two–phase flow and ignoring the air. As result,
his analysis is in the twilight zone not in the real world.
2 Or when the scientific principles simply dictate.
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