Hydrodynamic Drag Force Exerted on a Moving Floc and Its Implications to Free-Settling Test

doi:10.1016/S0043-1354(97)00320-5

淡江大學機構典藏 > 工學院 > 化學工程與材料工程學系暨研究所 > 期刊論文 > Item 987654321/88185

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Title:	Hydrodynamic Drag Force Exerted on a Moving Floc and Its Implications to Free-Settling Test
Authors:	Wu, R. M.;Lee, D. J.
Contributors:	淡江大學化學工程與材料工程學系
Keywords:	drag force;floc free-settling;FIDAP;Stokes' law
Date:	1998-03
Issue Date:	2013-04-13 15:20:33 (UTC+8)
Publisher:	I W A Publishing
Abstract:	This paper numerically evaluates the hydrodynamic drag force exerted on an individual floc moving steadily through an quiescent Newtonian fluid over a wide range of Reynolds numbers. The floc is modelled as a highly porous sphere, whose interior flow field is governed by the combined Darcy–Brinkman model; while the bulk fluid field is governed by Navier–Stokes equations. We used a computational fluid dynamics software, FIDAP 7.5, to solve the fluid field within and around the moving floc, from which the corresponding hydrodynamic drag force exerted on the floc is subsequently obtained. When the floc permeability is rather high, which is usually the case for activated sludge flocs, the drag force was found to be inversely proportional to the floc Reynolds number. The floc density versus size relationship obtained on the basis of the Stokes law-like correlation is thereby applicable to estimate the flocs' fractal dimension, however, is erroneous for estimating the floc density. This paper numerically evaluates the hydrodynamic drag force exerted on an individual floc moving steadily through an quiescent Newtonian fluid over a wide range of Reynolds numbers. The floc is modelled as a highly porous sphere, whose interior flow field is governed by the combined Darcy–Brinkman model; while the bulk fluid field is governed by Navier–Stokes equations. We used a computational fluid dynamics software, FIDAP 7.5, to solve the fluid field within and around the moving floc, from which the corresponding hydrodynamic drag force exerted on the floc is subsequently obtained. When the floc permeability is rather high, which is usually the case for activated sludge flocs, the drag force was found to be inversely proportional to the floc Reynolds number. The floc density versus size relationship obtained on the basis of the Stokes law-like correlation is thereby applicable to estimate the flocs' fractal dimension, however, is erroneous for estimating the floc density.
Relation:	Water research 32(3), pp.760–768
DOI:	10.1016/S0043-1354(97)00320-5
Appears in Collections:	[化學工程與材料工程學系暨研究所] 期刊論文

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