Document Type


Date of Award

Summer 2017

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)


Mechanical and Industrial Engineering

First Advisor

Pushpendra Singh

Second Advisor

Ian Sanford Fischer

Third Advisor

Daniel E. Bunker

Fourth Advisor

Siva P.V. Nadimpalli

Fifth Advisor

I. Joga Rao

Sixth Advisor

Anthony D. Rosato

Seventh Advisor

Shawn Alexander Chester


This dissertation work describes the physics of particle adsorption and the spontaneous dispersion of powders that occurs when they come in contact with a fluid-liquid interface and its application in hydrophilous pollination of Ruppia Maritima, an aquatic plant. The dispersion of particles can occur so quickly that it appears explosive, especially for small particles on the surface of mobile liquids like water. PIV (Particle Image Velocimetry) measurements show that the adsorption of a spherical particle at the interface causes an axisymmetric streaming flow about the vertical line passing through the particle center. The fluid directly below the particle rises upward, and near the surface, it moves away from the particle. The flow, which develops within a fraction of a second after the adsorption of the particle, persists for several seconds. The flow strength, and the volume over which it extends, decrease with decreasing particle size. The streaming flow induced by the adsorption of two or more particles is a combination of the flows which they induce individually. The flow causes particles sprinkled together onto a liquid surface to disperse, as well as to hydrodynamic stresses which is extensional in the plane tangential to the interface and compressive in the normal direction. The stresses can cause the breakup of particle agglomerates when they are adsorbed on a liquid surface.

The physics underlying the mechanisms of two-dimensional aquatic pollen dispersal, known as hydrophily is also studied and presented here. The aquatic pollination has evolved in several genera of aquatic plants, including Halodule, Halophila, Lepilaena, and Ruppia. Ruppia maritima, which is native to salt and brackish waters circumglobally, is selected for this study. Two mechanisms are observed, by which the pollen released from male inflorescences of Ruppia is adsorbed on a water surface: 1) inflorescences rise above the water surface and after they mature their pollen mass falls onto the surface as clumps and disperses as it comes in contact with the surface; 2) inflorescences remain below the surface and produce air bubbles which carry pollen mass to the surface where it disperses. In both cases dispersed pollen masses combined with others under the action of lateral capillary forces to form pollen rafts. The formation of porous pollen rafts increases the probability of pollination since the attractive capillary force on a pollen raft toward a stigma is much larger than on a single pollen grain. The presence of a trace amount of surfactant can disrupt the pollination process as the pollen is not captured or transported on the water surface.



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