Isothermal flow is a model of
compressible fluid flow whereby the flow remains at the same
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied on ...
while flowing in a conduit.
[Shapiro, A.H., ''The Dynamics and Thermodynamics of Compressible Fluid Flow, Volume 1'', Ronald Press, 1953.] In the model,
heat
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...
transferred through the walls of the conduit is offset by
friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding (motion), sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative la ...
al heating back into the flow. Although the flow
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied on ...
remains constant, a change in stagnation temperature occurs because of a change in velocity. The interesting part of this flow is that the flow is choked at
and not at
Mach number
Mach number (M or Ma) (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound.
It is named after the Moravian physicist and philosopher Ernst Mach.
: \mathrm = \ ...
equal to one as in the case of many other model such as
Fanno flow. This fact applies to real gases as well as ideal gases.
For an important practical case of a
gas flow through a long tube, the model has an applicability in situations which occurs in a relatively long distance and where heat transfer is relatively rapid so that the temperature can be treated, for engineering purposes, as a constant. This model has also applicability as upper boundary to
Fanno flow.
See also
*
Fanno flow
*
Isentropic process
*
Rayleigh flow
References
{{Reflist
External links
Fundamentals of compressible Flow
Fluid dynamics