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Turbulent Pipe Flow (turbulent + pipe_flow)

Distribution by Scientific Domains

Chemistry	80%
Engineering	20%

Selected Abstracts

Fluid flow and heat transfer characteristics of cone orifice jet (effects of cone angle)

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2009
Mizuki Kito
Abstract The use of a jet from an orifice nozzle with a saddle-backed-shape velocity profile and a contracted flow at the nozzle exit may improve the heat transfer characteristics on an impingement plate because of its larger centerline velocity. However, it requires more power to operate than a common nozzle because of its higher flow resistance. We therefore initially considered the use of a cone orifice nozzle to obtain better heat transfer performance as well as to decrease the flow resistance. We examined the effects of the cone angle , on the cone orifice free jet flow and heat transfer characteristics of the impinging jet. We compared two nozzles: a pipe nozzle and a quadrant nozzle. The first one provides a velocity profile of a fully developed turbulent pipe flow, and the second has a uniform velocity profile at the nozzle exit. We observed a significant enhancement of the heat transfer characteristics of the cone orifice jets at Re=1.5×104. Using the cone orifice impinging jets enhanced the heat transfer rates as compared to the quadrant jet, even when the jets were supplied with the same operational power as the pipe jet. For instance, a maximum enhancement up to approximately 22% at r/do,0.5 is observed for ,=15°. In addition, an increase of approximately 7% is attained as compared to when the pipe jet was used. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20243 [source]

Large eddy simulation of turbulent concentric annular channel flows

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2004
Nan-Sheng Liu
Abstract Fully developed turbulent concentric annular channel flow has been investigated numerically by use of large eddy simulation (LES) technique coupled with a localized one-equation dynamic subgrid-scale (SGS) model. The objective of this study is to deal with the behaviour of turbulent flow near the inner and outer walls of the concentric annular channel and to examine the effectiveness of LES technique for predicting the turbulent flow influenced by the transverse curvature effect. The computations are performed for the Reynolds number Re,=180, 395 and 640, based on an averaged friction velocity and the annular channel width with the inner and outer cylinder radius being Ri=1 and Ro=2. To validate the present approach, calculated results for turbulent pipe flow and concentric annular channel flow are compared with available experimental data and direct numerical simulation results, which confirms that the present approach can be used to study turbulent concentric annular channel flow satisfactorily. To elucidate turbulence characteristics in the concentric annular channel, some typical quantities, including the resolved velocity, turbulence intensity, turbulent eddy viscosity, SGS kinetic energy, SGS dissipation rate, Reynolds stress budgets, and turbulence structures based on the velocity fluctuations, are analysed. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Modeling of turbulent precipitation: A transported population balance-PDF method

AICHE JOURNAL, Issue 4 2010
Giovanni di Veroli
Abstract Turbulent precipitation is a complex problem, whose mathematical description of precipitation requires a coupling of fluid dynamics with the population balance equation (PBE). In the case of turbulent flow, this coupling results in unclosed equations due to the nonlinear nature of precipitation kinetics. In this article, we present a methodology for modeling turbulent precipitation using the concept of the transported probability density function (PDF) in conjunction with a discretized PBE, simulated via a Lagrangian stochastic method. The transported PBE-PDF approach resolves the closure problem of turbulent precipitation for arbitrarily complex precipitation kinetics, while retrieving the full particle size distribution (PSD). The method is applied to the precipitation of BaSO4 in a turbulent pipe flow and comparisons are made with the experimental results of Baldyga and Orciuch (Chem Eng Sci. 2001;56:2435-2444) showing excellent agreement, while insight is drawn into the mechanisms that determine the evolution of the product PSD. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Polymer flocculation of calcite: Experimental results from turbulent pipe flow

AICHE JOURNAL, Issue 4 2006
Alex R. Heath
Abstract The kinetics of aggregation/breakage of calcite particles flocculated with a high-molecular-weight polymer flocculant has been studied in turbulent pipe flow. The mean flocculation residence time was varied by changing the length of pipe between the flocculant injection point and the in-stream particle-sizing probe (Lasentec FBRM). A variety of pipe sizes and flow rates were used to produce a range of mean fluid shear rates. The mean shear rate was calculated from the pressure drop along the pipe reactor, as measured by manometer, and was found to vary markedly as a function of both the solid fraction and aggregate size. Increased fluid shear increased the initial mixing and aggregation rates, but ultimately lead to a reduced final aggregate size due to increased aggregate breakage. Several other process variables were also studied, with the aggregate size increased with flocculant dosage and primary particle size, but reduced at higher solid fraction. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source]

CFD modeling of heat transfer in turbulent pipe flows

AICHE JOURNAL, Issue 9 2000
S. S. Thakre
Twelve versions of low Reynolds number k-, and two low Reynolds number Reynolds stress turbulence models for heat transfer were analyzed comparatively. Predictions of the mean axial temperature, the radial and axial turbulent heat fluxes, and the effect of Prandtl number on Nusselt number were compared with the experimental data. The model by Lai and So from the k-, group and Lai and So from the Reynolds stress group had the best overall predictive ability for heat transfer in turbulent pipe flow. The Lai and So model was attributed to its success in the predictions of flow parameters such as mean axial velocity, turbulent kinetic energy, eddy diffusivity, and the overall energy dissipation rate. The k-, models performed relatively better than the Reynolds stress models for predicting the mean axial temperature and the Nusselt number. This qualitative and quantitative study found the need for more sophisticated near-wall experimental measurements and the accuracy of the dissipation (of turbulent energy) and the pressure-scrambling models. [source]

Experimental research on drag reduction by polymer additives in a turbulent pipe flow

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2002
Shao Xueming
Abstract In order to investigate the effects of injection position on drag reduction as well as further the effects of polymer additives on turbulent structures, LDA measurements of turbulent pipe flows were conducted. The results show that the amount of drag reduction grows with the increase of the Reynolds number, and injecting the polymer at the centre of pipe is more effective than at the wall. Due to the addition of polymer solution, the axial, radial r.m.s. velocity fluctuations and Reynolds stress decrease over the entire pipe cross-section, the time auto-correlation coefficients of axial and radial velocity fluctuation at the centre of pipe decay more slowly, the number of spectrum peaks is decreased, and the peak shifts towards lower wave numbers. The results also reveal that, due to the addition of polymer solution, the large-scale vortices are enhanced and small-scale vortices are suppressed. On a effectué des mesures par anémométrie laser Doppler d'écoulements turbulents dans des conduites afin d'étudier l'effet de la position de l'injection et l'effet de l'ajout d'additifs à base de polymères sur la réduction de traînée. Les résultats montrent que la réduction de traînée augmente avec le nombre de Reynolds et qu'il est plus efficace d'injecter le polymère au centre de la conduite qu'à la paroi. Du fait de l'ajout d'une solution de polymères, les fluctuations de vitesse efficace radiale et axiale et la contrainte de Reynolds diminuent sur toute la section transversale de la conduite, les coefficients d'auto-corrélation de temps de la fluctuation de vitesse efficace radiale et axiale au centre de la conduite décroissent plus lentement, le nombre de pics du spectre diminue et les pics tendent à avoir un nombre d'ondes moins grand. Les résultats montrent également que, grâce à l'ajout de la solution de polymères, les tourbillons de grande échelle sont plus nombreux tandis que les tourbillons de petite eéhelle disparaissent. [source]

A low reynolds number k-, modelling of turbulent pipe flow: Flow pattern and energy balance

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2001
Shirish S. Thakre
Abstract The present paper addresses a comparative analysis of twelve different versions of low Reynolds number k -, turbulence models. The predictive capability of the models have been tested on the basis of the flow patterns and energy balance. Numerical simulations were performed at the Reynolds numbers of 7400, 22 000 and 500 000. The predicted mean axial velocity and turbulent kinetic energy were compared with the experimental data of Durst et al. (1995) and Schildknecht et al.(1979) for the Reynolds number of 7400 and 22000 respectively. The overall energy balance was established at three Reynolds numbers of 7400, 22 000 and 500000. A comparison of all the models has been predicted. On décrit dans cet article une analyse comparative de douze versions différentes de modèles de turbulence à faibles nombres de Reynolds k -,. La capacité de prédiction de ces modèles a été testée d'après les profils d'écoulement et le bilan énergétique. Des simulations numériques ont été réalisées à des nombres de Reynolds de 7400, 22 000 et 500 000. La vitesse axiale et l'énergie cinétique turbulente moyennes prédites ont été comparées aux données expérimentales de Durst et al. (1995) et Schildknecht et al. (1979) pour les nombres de Reynolds de 7400 et 22 000, respectivement. Le bilan énergétique global a été établi pour les trois nombres de Reynolds. Une comparaison de tous les modèles a été effectuée. [source]

Drag enhancement of aqueous electrolyte solutions in turbulent pipe flow

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007
E. Benard
Abstract Experimental measurements have indicated that drag enhancement occurs when aqueous electrolyte solutions are flowing in the turbulent regime. The primary electroviscous effect due to the distortion by the shear field of the electrical double layer surrounding the ions in solution is invoked to explain the drag enhancement. Calculations using the Booth model for symmetrical one-to-one electrolytes enabled the increased viscosity in the turbulent regime to be calculated. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd. [source]