arXiv subjects

Lawrence A. Hough

Publications and source records attributed to Lawrence A. Hough.

3 recordsLinked to original sources

arXiv2019

Preferential Root Tropism Induced by Structural Inhomogeneities in 2D Wet Granular Media

We investigate certain aspects of the physical mechanisms of root growth in a granular medium and how these roots adapt to changes in water distribution induced by the presence of structural inhomogeneities in the form of solid intrusions. Physical intrusions such as a square rod added into the 2D granular medium modify water distribution by maintaining robust capillary action, pumping water from the more saturated areas at the bottom of the cell towards the less saturated areas near the top of the cell while the rest of the medium is slowly devoid of water via evaporation. This water redistribution induces `preferential tropism' of roots, guiding the roots and permitting them to grow deeper into more saturated regions in the soil. This further allows more efficient access to available water in the deeper sections of the medium thereby resulting to increased plant lifetime

cond-mat.soft↗

arXiv2018

Effect of geometry on the dewetting of granular chains by evaporation

Understanding evaporation or drying in granular media still remains complex despite recent advancements. Evaporation depends on liquid transport across a connected film network from the bulk to the surface. In this study, we investigate the stability of film networks as a function of granular packing. Using a controlled experimental approach, we vary the granular packing geometry and show the changes in the height of the liquid film network during evaporation as packing shifts from a loose-packed to a close-packed arrangement. This height can be calculated from an equilibrium between hydrostatic pressure and the pressure difference between two points in the vertical film network. We use a simulation approach to calculate the pressure in both the percolating front and evaporating front within the two-phase zone of air/water mixture. Results show good agreement between the model and the experiment.

cond-mat.soft↗

arXiv2014

Diagnosing hyperuniformity in two-dimensional disordered jammed-packings of soft spheres

Hyperuniformity characterizes a state of matter for which density fluctuations diminish towards zero at the largest length scales. However, the task of determining whether or not an experimental system is hyperuniform is experimentally challenging due to finite-resolution, noise and sample-size effects that influence characterization measurements. Here we explore these issues, employing video optical microscopy to study hyperuniformity phenomena in disordered two-dimensional jammed packings of soft spheres. Using a combination of experiment and simulation we characterize the detrimental effects of particle polydispersity, image noise, and finite-size effects on the assignment of hyperuniformity, and we develop a methodology that permits improved diagnosis of hyperuniformity from real-space measurements. The key to this improvement is a simple packing reconstruction algorithm that incorporates particle polydispersity to minimize free volume. In addition, simulations show that hyperuniformity can be ascertained more accurately in direct space than in reciprocal space as a result of finite sample-size. Finally, experimental colloidal packings of soft polymeric spheres are shown to be hyperuniform.

cond-mat.soft↗