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Pipe flow

About: Pipe flow is a research topic. Over the lifetime, 13826 publications have been published within this topic receiving 351605 citations.


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Patent
16 Sep 1994
TL;DR: In this article, a modular micro-channel heat exchanger for cooling a heated region and a method for making the device was presented, which features an array of thin copper sheets which are etched with rows of elongated holes that pierce the sheets, coated with silver and held together with the holes aligned.
Abstract: A modular microchannel heat exchanger for cooling a heated region and a method for making the device. A first section of the device features an array of thin copper sheets which are etched with rows of elongated holes that pierce the sheets, coated with silver and held together with the holes aligned. These holes form a microchannel having a desired aspect ratio. A second section of the device has a series of thin copper plates which are etched as apertures, coated with silver and stacked in a sequence on the sheets of the first section, the plate closest to the sheets having elongated apertures oriented transversely to the microchannel of the sheets, the apertures combining further from the sheets into circular apertures to fit a coaxial inlet and outlet conduit where unitary or pipe flow occurs. The inlet conduit is, through the branching series of plates, in communication with alternately spaced elongated apertures adjacent to the microchannel of the sheets, and the outlet conduit is in communication with the other alternate elongated apertures. A case for both sections has an inlet and outlet chamber with holes that the inlet and outlet conduits plug into.

171 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the dynamical behavior of tiny elongated particles in a directly simulated turbulent flow field and obtained the time evolution of the particle orientation and translational and rotational motions in a statistically steady channel flow for six different particle classes.
Abstract: The dynamical behavior of tiny elongated particles in a directly simulated turbulent flow field is investigated. The ellipsoidal particles are affected both by inertia and hydrodynamic forces and torques. The time evolution of the particle orientation and translational and rotational motions in a statistically steady channel flow is obtained for six different particle classes. The focus is on the influence of particle aspect ratio λ and the particle response time on the particle dynamics, i.e., distribution, orientation, translation, and rotation. Both ellipsoidal and spherical particles tend to accumulate in the viscous sublayer and preferentially concentrate in regions of low-speed fluid velocity. The translational motion is practically unaffected by the aspect ratio, whereas both mean and fluctuating spin components depend crucially on λ. The ellipsoids tend to align themselves with the mean flow direction and this tendency becomes more pronounced in the wall proximity when the lateral tilting of the elongated particles is suppressed.

171 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss the rapid damping of pressure peaks in a water-hammer phenomenon after the end of a complete valve-closure maneuver, which is due to flow characteristics not considered when one-dimensional models are employed.
Abstract: The paper discusses the rapid damping of pressure peaks in a water-hammer phenomenon after the end of a complete valve-closure maneuver. This effect is due to flow characteristics not considered when one-dimensional models are employed. Such an effect is linked to the cross-sectional velocity profiles, and therefore to the intrinsic two-dimensionality of the flow field. Applying a 2-D model, recently proposed in the literature, to expand the limited experimental data available with numerical results, useful information on the evolution of the velocity profiles during a transient has been obtained. Starting from an in-depth inspection of the terms in the momentum equation, an additional term is introduced to model the effects of the flow-field two-dimensionality in a 1-D formulation. Finally, the adequacy of a relationship previously proposed by the writers to evaluate the additional term is specifically showed for fast transients in the field of low-Reynolds-number flows when no cavitation occurs, even if its validity has been proven elsewhere for rather different conditions.

171 citations

Journal ArticleDOI
TL;DR: In this paper, detailed turbulent flow measurements were made in a plane channel with a one-sided 50% abrupt expansion, which acted as a backward-facing step, and various turbulent statistics and the energy budget were calculated from numerous instantaneous vector distributions.

170 citations

Journal ArticleDOI
TL;DR: In this paper, a quasi-two-dimensional model for unsteady flow analysis in pipes and pipe networks is presented, based on the mixing length hypothesis in the turbulent zone and on Newton's law in the viscous sublayer.
Abstract: A quasi-two-dimensional model for unsteady-flow analysis in pipes and pipe networks is presented. The turbulence model is based on the mixing length hypothesis in the turbulent zone and on Newton’s law in the viscous sublayer. An expression of the mixing length in terms of the Reynolds number and an expression of the parameter of logarithmic law of the wall in terms of the friction Reynolds number are found from Nikuradse’s experimental data. An implicit numerical scheme for the integration of the equations is proposed to overcome the limitations of the explicit schemes. Uniqueness of the head and continuity of discharge are considered at the junctions. The results of both a quasi-steady 1D model and a quasi-2D model are compared with results from a laboratory network. For these experimental runs, the comparisons show that the average relative errors on the maximum head oscillations are 19.1% with the 1D model and 8.6% with the quasi-2D model; those on the minimum oscillations are 19.2% with the 1D model and 5.3% with the quasi-2D model. The latter model is in better agreement because it takes into account the velocity profile, thus allowing for a more accurate evaluation of the shear stress.

170 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202335
202275
2021170
2020177
2019273
2018281