Abstr:Pipe flow - rotating

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This UFR contains a lot of valuable information and is therefore retained. But, it needs further development.


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Confined Flows

Underlying Flow Regime 4-03

Abstract

The study of turbulent flows through a pipe rotating about its axis is of interest for several flows in practical applications, for instance in combustors or rotating machineries and cooling systems of rotors. For example an application is a rotating power transmission shaft that is longitudinally bored and through which a fluid is pumped for cooling. Furthermore, the rotating pipe is a very good candidate to help in understanding swirling flows, which are important in applications connected to combustion and aeroacoustic. In addition, rotating flows occur in geophysical applications and the effects of solid body rotation on turbulence in a pipe presents similarities with three-dimensional boundary layers of practical importance, such as on swept wings of airplanes. When a fluid enters a pipe rotating about its axis, tangential shear forces, acting between the wall and the fluid, cause the fluid to rotate with the pipe, resulting in a flow pattern different from that observed in a stationary pipe. Rotation reduces the turbulence in the wall region and increase it in the outer region for the effects of centrifugal forces.

Experimental results indicate that the rotation changes the mean axial velocity profile, tending towards the parabolic profile characteristics of laminar flows. In addition the creation of a mean azimuthal velocity, in the reference frame of the rotating pipe, makes this flow no any longer unidirectional. This component, negligible from the engineering point of view, allows to investigate the performances of turbulence models.

Turbulent flow in pipes has been a popular benchmark case for the testing and evaluation of both theories and models of turbulence during the past century. One of the first notable examples was the mixing length theory of Prandtl (1925) which was partially validated using early turbulent pipe flow data approximately seventy years ago.


Contributors: Stefano Leonardi - Universita di Roma 'La Sapienza'


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