Statistical characteristics of particles on a liquid surface Backer, Lara; Moreno, Sofia
The purpose of this project was to measure statistical properties of a multi-particle system of rod-like particles, approximately 10mm in length and 1mm in diameter, placed on the surface of a fluid in a funnel as it drains, serving to hasten the surface tension effects due to the “Cheerios Effect”. Top-view images of the system were automatically captured as the experiment progressed and the fluid drained. Approximately five images were selected from fifteen experiments. The particles in the images were identified using MATLAB and Image J, and the data was run through MATLAB scripts that generated radial, orientation, and void area (areas of fluid enclosed by particles) distribution plots that denoted the packing efficiency of the particles. The radial distribution plots, denoting the probability density of particles encountered at different distances from a reference particle were found to be more or less independent of initial configuration and the rate of the fluid draining from the funnel; in all experiments, the probability of encountering a particle at a distance of one particle width increased over time. Similarly, for orientation distribution plots, the initial configuration and rate of fluid draining did not seem to have a large impact on the final configuration of particles, but it was noted that at the end of experiments, the particles tended to be oriented in the same direction, particularly for particles at one particle width from each other, as expected. The void area distributions indicated that the cylindrical particles tend to pack efficiently because the number of smaller void areas increased with time for all experiments, found by comparing the initial void area distribution to the final distribution. Running experiments with different initial particle concentrations (numbers of particles present) and measuring the radial, orientation, and void area distributions would further support or contradict results of this project, which indicate that the final configuration’s distribution functions would always be the same. Furthermore, the method of detecting void areas can be improved to distinguish void areas which are almost enclosed by particles, but due to a small connection to a larger void area are not considered isolated. This could provide a better gauge of the packing efficiency of the cylindrical particles.
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