三維模擬兩同軸與平行多孔球在水中沉降之受力分析

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Title:	三維模擬兩同軸與平行多孔球在水中沉降之受力分析
Other Titles:	Three dimensional simulations of hydrodynamic drag forces on two porous spheres settling parallel or in-line
Authors:	林勉宏;Lin, Mien-hung
Contributors:	淡江大學化學工程與材料工程學系碩士班吳容銘;Wu, Rome-ming
Keywords:	三維;模擬;透過率;同軸;平行;拖曳力;three dimension;simulation;permeability;in-line;parallel;drag force
Date:	2006
Issue Date:	2010-01-11 05:44:02 (UTC+8)
Abstract:	本論文為兩同軸或平行多孔球在牛頓流體中穩定移動的流體拖曳力的數值估計，雷諾數範圍從0.1到40。對於兩同軸多孔球，在緩流範圍中，兩球體的拖曳力幾乎一樣。在較高的雷諾數，第一顆球的拖曳力會高於後面的球，因為第一顆球對於第二個球有遮蔽的影響。當直徑b<2(b=df/2k^0.5,df跟k分別為球的直徑跟透過率)，兩球體可視為非球體限制。增加兩球的b值，第二個球的拖曳力會增加，因為球內部的透過率較低；同時由於第一個球產生的強烈的遮蔽效應造成第二個球所受的拖曳力會降低，此兩種效應相互影響，導致第二個球的受力很難判斷，而當b值最小時，上述的影響會最小；平行沉降中兩球的受力幾乎相同，孔隙度(e)的影響遠大於兩多孔球間的影響，緻密多孔球的沉降速度比疏鬆多孔球的沉降速度快 This paper numerically evaluates the hydrodynamic drag force exerted on two highly porous spheres moving steadily parallel or in-line through a quiescent Newtonian fluid over a Reynolds number ranging from 0.1 to 40. At creeping flow limit, the drag forces exerted on both spheres were approximately identical. At higher Reynolds numbers the drag force on the leading sphere (sphere #1) was higher than the following sphere (sphere #2), revealing the shading effects produced by sphere #1 on sphere #2. At dimensionless diameter b<2 (b=df/2k^0.5, df and k are sphere diameter and interior permeability, respectively), the spheres can be regarded as “no-spheres” limit. At increasing b for both spheres, the drag force on sphere #2 was increased because of the more difficult advective flow through its interior, and at the same time the drag was reduced owing to the stronger wake flow produced by the denser sphere #1. The competition between these two effects leads to complicated dependence of drag force on sphere #2 on b value. These effects were minimal when b became low. In parallel settling, the forces of the two spheres force are nearly the same. The influence of porosity is larger than that of distances between the two porous spheres. The settling velocity of dense porous sphere is faster than highly porous sphere.
Appears in Collections:	[Graduate Institute & Department of Chemical and Materials Engineering] Thesis

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