Particles trapped at a fluid-fluid interface by capillary forces can form a monolayer that jams and buckles when subject to uniaxial compression. Here we investigate experimentally the buckling mechanics of monolayers of millimeter-sized rigid plates trapped at a planar fluid-fluid interface subject to uniaxial compression in a Langmuir trough. We quantified the buckling wavelength and the associated force on the trough barriers as a function of the degree of compression. To explain the observed buckling wavelength and forces in the two-dimensional (2D) monolayer, we consider a simplified system composed of a linear chain of platelike particles. The chain system enables us to build a theoretical model which is then compared to the 2D monolayer data. Both the experiments and analytical model show that the wavelength of buckling of a monolayer of platelike particles is of the order of the particle size, a different scaling from the one usually reported for monolayers of spheres. A simple model of buckling surface pressure is also proposed, and an analysis of the effect of the bending rigidity resulting from a small overlap between nanosheet particles is presented. These results can be applied to the modeling of the interfacial rheology and buckling dynamics of interfacial layers of 2D nanomaterials.

@en

We experimentally and numerically study the dynamics of a liquid jet issued from a rotating orifice, whose breakup is regulated by a vibrating piezo element. The helical trajectory of the spiralling jet yields fictitious forces varying along the jet whose longitudinal projections stretch and thin the jet, affecting the growth of perturbations. We show that by quantifying these fictitious forces, one can estimate the jet intact length and size distribution of drops formed at jet breakup. The presence of the locally varying fictitious forces may render high-frequency perturbations, that would otherwise be stable in the abscence of stretching, unstable, as observed similarly in the case of straight jets stretching under gravity. The perturbation amplitude then dictates how strong the perturbation is coupled to the jet compared with random noise that is inherently present in any experimental set-up. In the present study we exploit the slenderness of the jet to separate the calculation of the base flow and the growth of perturbations. The fictitious forces calculated from the base flow trajectory are then used in a nonlinear slender-jet model, which treats the spiralling jet as a quasi-straight jet with locally varying body forces. We show both experimentally and numerically that jet breakup characteristics (e.g. intact length and drop size distribution) can be controlled by finite-amplitude perturbations created by mechanically induced pressure modulations. Finally, we revisit the integrated net gain approach developed for straight jets under gravity and we provide simple analogous relations for spiralling jets.@en

The paper presents experimental data and results from a prediction tool for the performance of a desiccant loop cooling system. The experiments are performed under a variety of high humidity and hot ambient conditions and the system performance is described. One of the experimental conditions is typical of many Indian cities and the systems appropriate for those cities are established. A simulation program that can predict the performance of the desiccant loop is developed. The simulation results show that this system can work as effectively as vapor compression air-conditioning for certain ambient conditions whereas it can function as a pre-cooler to a vapor compression system under more severe conditions, resulting in a reduced power consumption. The results presented in the paper give a guideline to practicing engineers as to when a desiccant loop cooling system would be useful. A simple payback analysis and a lifecycle cost analysis shows that a desiccant cooling system with a waste heat recovery recuperator is an economically viable investment.

@en