Multiple states of finger propagation in partially occluded tubes

International audienc

Oscillatory bubbles induced by geometrical constraint

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Soft Dynamics simulation: 2. Elastic spheres undergoing a T1 process in a viscous fluid

Robust empirical constitutive laws for granular materials in air or in a viscous fluid have been expressed in terms of timescales based on the dynamics of a single particle. However, some behaviours such as viscosity bifurcation or shear localization, observed also in foams, emulsions, and block copolymer cubic phases, seem to involve other micro-timescales which may be related to the dynamics of local particle reorganizations. In the present work, we consider a T1 process as an example of a rearrangement. Using the Soft dynamics simulation method introduced in the first paper of this series, we describe theoretically and numerically the motion of four elastic spheres in a viscous fluid. Hydrodynamic interactions are described at the level of lubrication (Poiseuille squeezing and Couette shear flow) and the elastic deflection of the particle surface is modeled as Hertzian. The duration of the simulated T1 process can vary substantially as a consequence of minute changes in the initial separations, consistently with predictions. For the first time, a collective behaviour is thus found to depend on another parameter than the typical volume fraction in particles.Comment: 11 pages - 5 figure

Initiation of underwater granular avalanches: Influence of the initial volume fraction

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Design and experimental analysis of an Integral Collector Storage (ICS) prototype for DHW production

This paper presents an innovative solar ICS (Integral Collector Storage) for the production of Domestic Hot Water (DHW). The novelty consists in combining an absorbent surface, heat pipes and a storage cavity made up of a phase change material (PCM) within a single compact casing. The energy performance of the system was experimentally studied in different seasons of the year, with and without domestic hot water production. The temperatures inside the collector were monitored using K-type thermocouples and their trends were analysed and discussed. During the experimental phase, the thermal storage reached the maximum temperature of 79.3 °C, exploiting the latent heat of the PCM. Overall performances demonstrated good agreement with results available in the literature in terms of efficiency and energy storage. A specific heat flux of 2.64 kW·m−2 was achieved in DHW production, with a water flowrate of 0.87 kg·min−1. The 0.02 m3 PCM section was able to store 24.57 kWh of thermal energy along a monitored month. Future developments of this new technology include new experimental tests with larger prototypes and the coupling with a real user

Study of a New Integrated Solar Collector

International audienc