Internal flow

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{{short description|Fluid flow within a fully confined region}}

In fluid mechanics, internal flow is a flow wherein the fluid is completely confined by inner surfaces of an item (e.g. a tube).{{cite book |last1=Çengel |first1=Yunus A. |title=Heat and Mass Transfer : Fundamentals and Applications. |date=2014 |publisher=McGraw-Hill Higher Education |location=NY |isbn=9780077654764 |pages=449 |edition=5th}} Hence the boundary layer is unable to develop without eventually being constrained. The internal flow configuration represents a convenient geometry for heating and cooling fluids used in chemical processing, environmental control, and energy conversion technologies. Internal flow is fully dominated by viscosity throughout the flow field.{{Cite book |last=Çengel |first=Yunus A. |title=Fluid mechanics: fundamentals and applications |last2=Cimbala |first2=John M. |date=2006 |publisher=McGraw-Hill Higher Education |isbn=978-0-07-247236-3 |series=McGraw-Hill series in mechanical engineering |location=Boston, Mass. |page=10}}

An example includes flow in a pipe.