Settling and breakup of suspension drops

Abstract

A suspension drop is an initially spherical swarm of small particles that are suspended in fluid at rest. Under the influence of gravity this drop settles, and it can undergo a complex shape evolution with subsequent disintegration. We performed numerical simulations of suspension drops settling at moderate drop Reynolds numbers 1 ഛ Re d ഛ 100. 1 Here, we show two typical examples of the drop breakup. Figure 1 displays the initial drop ͑left͒ and the settling drop very shortly after the release ͑right͒. The particles are colorcoded to visualize their motion inside the drop. This initial stage is similar for all drop Reynolds numbers. However, the subsequent shape evolution and disintegration strongly depend on the Reynolds number. In the case of very small Reynolds numbers, Re d Ӷ 1, the drop retains a compact spherical shape and a few particles leak into a tail emanating from the rear of the drop ͑not shown here͒. In the case of Re d = 1 the drop deforms into a torus that grows in diameter while settling. Eventually two bulges form and the torus breaks up into two secondary blobs ͑Fig. 2͒. In the case of Re d = 100 the disintegration process occurs much faster than in the foregoing example. Also, the torus is now spanned by a membrane of dilute particles and finally breaks up into a larger number of secondary blobs ͑Fig. 3͒. 1 T. Bosse, C. Härtel, E. Meiburg, and L. Kleiser, "Numerical simulation of finite Reynolds number suspension drops settling under gravity," Phys. Fluids 17, 037101 ͑2005͒. FIG. 1. ͑Enhanced online͒. Initial drop ͑left͒ and settling drop very shortly after the release ͑right͒. FIG. 2. Breakup of suspension drop settling at Re d =1. FIG. 3. Breakup of suspension drop settling at Re d =100.

Colloid Transport in Porous Media: A Review of Classical Mechanisms and Emerging Topics

“…The complex shape evolution undergone by colloids swarms and vortex rings is well known [221,222,224,227,230,231,[240][241][242][243] and includes formation of a ring as an intermediate stage. The most interesting and relevant feature is bifurcation of the swarm into two (or more) smaller swarms.…”