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 ?
For incompressible flow, low Mach number suggests that the time step size is of the second order of grid size in LBM.
With these types of machines supersonic flows are present and there is no longer the ability to make the assumption of incompressible flow as with most fan test rigs in educational environments.
For the incompressible flow of a Newtonian fluid with constant properties considered in this case, the flow governing equations in orthogonal Cartesian coordinates are as follows:
[16] Harlow, F.H., Welch, J.E., 1965, "Numerical Calculation of Time Dependent Viscous Incompressible Flow of Fluid with Free surface," Phys.
"Geometric linking, independent of linking number, can be used to estimate a lower bound on the energy of an incompressible flow," Freedman says.
Numerical simulations of mixed convective incompressible flow in a horizontal plane channel with adia-batic walls over two isothermal tandem circular cylinders of equal size are presented to investigate the effect of wall proximity of obstacles, gap space (i.
For incompressible flow, the Navier-Stokes equation in the presence of Coriolis force is given by
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 author has organized the fifteen chapters that make up the main body of his text in three parts devoted to the basics, more types of fluids, and more algorithms.
The research on numerical schemes for approximating viscous incompressible flow problems has been and is very active since the 1960s, when computational fluid dynamics was launched.
Notsu, "Incomplete balancing domain decomposition for large scale 3-D nonstationary incompressible flow problems," in Proceedings of the 9th World Congress on Computational Mechanics and 4th Asian Pacific Congress on Computational Mechanics, 2010.
Sani, Incompressible Flow and the Finite Element Method, John Wiley & Sons, 2000.
For incompressible flow, in the flow process, the density [rho] of each dot is always unchanged, that is, [partial derivative][rho]/[partial derivative]t = 0 and [rho] [not equal to] 0; the form of the continuity equation of incompressible fluid can be derived as