# incompressible flow

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## Incompressible flow

Fluid motion with negligible changes in density. No fluid is truly incompressible, since even liquids can have their density increased through application of sufficient pressure. But density changes in a flow will be negligible if the Mach number, Ma, of the flow is small. This condition for incompressible flow is given by the equation below, where V is the fluid velocity and a is the speed of sound of the fluid. It is nearly impossible to attain Ma = 0.3 in liquid flow because of the very high pressures required. Thus liquid flow is incompressible. See Mach number

Gases may easily move at compressible speeds. Doubling the pressure of air—from, say, 1 to 2 atm—may accelerate it to supersonic velocity. In principle, practically any large Mach number may be achieved in gas flow. As Mach number increases above 0.3, the four compressible speed ranges occur: subsonic, transonic, supersonic, and hypersonic flow. Each of these has special characteristics and methods of analysis.

Air at 68°F (20°C) has a speed of sound of 760 mi/h (340 m/s). Thus inequality indicates that air flow will be incompressible at velocities up to 228 mi/h (102 m/s). This includes a wide variety of practical air flows: ventilation ducts, fans, automobiles, baseball pitches, light aircraft, and wind forces. The result is a wide variety of useful incompressible flow relations applicable to both liquids and gases. See Compressible flow, Fluid flow

## incompressible flow

[¦in·kəm′pres·ə·bal ′flō]
(fluid mechanics)
Fluid motion without any change in density.
References in periodicals archive ?
The Navier-Stokes and energy equations for two-dimensional incompressible flow in non-dimensional form are expressed as:
10] solved a laminar incompressible flow applying a fully coupled solver on an unstructured grid.
It is found that the distribution peak of the P value locates near zero, which indicates the distorted flame behind the shock wave mainly behaves as an incompressible flow.
What is more, for incompressible flow problems, the pressure term is implicit.
This study intends to investigate the steady, incompressible flow and heat transfer for viscous electrically conducting fluid.
Author Robert Bridson presents students, academics, researchers, and professionals working in a wide variety of contexts with the second edition of his examination of the techniques required to animate fully three-dimensional incompressible flow.
The equations in this work are from the adaptation of the method for incompressible flow described by Monaghan [30].
Thus, the problem of finding energy density distribution in space is reduced to the problem of finding the stretching statistics of a material surface (the wavefront) in incompressible flow field.
To distinguish between compressible and incompressible flow in gases, the Mach number (the ratio of the speed of the flow to the speed of sound) must be greater than about 0.
Terrill and Shrestha [1] considered the laminar incompressible flow of an electrically conducting viscous fluid through a porous channel and gave a solution for a large suction Reynolds number and Hartmann number.

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