| Summary: | 碩士 === 淡江大學 === 化學工程與材料工程學系碩士班 === 94 === 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.
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