Search results for "Fluid Dynamic"

RECUPERO ENERGETICO ALL’INTERNO DELLE RETI ACQUEDOTTISTICHE MEDIANTE MICROTURBINE IDRAULICHE

2022

Flow and Heat Transfer in Corrugated Passages: Direct and Large-Eddy Simulation and Comparison with Experimental Results

1993

The Origin of Non-thermal Fluctuations in Multiphase Flow in Porous Media

2021

Core flooding experiments to determine multiphase flow in properties of rock such as relative permeability can show significant fluctuations in terms of pressure, saturation, and electrical conductivity. That is typically not considered in the Darcy scale interpretation but treated as noise. However, in recent years, flow regimes that exhibit spatio-temporal variations in pore scale occupancy related to fluid phase pressure changes have been identified. They are associated with topological changes in the fluid configurations caused by pore-scale instabilities such as snap-off. The common understanding of Darcy-scale flow regimes is that pore-scale phenomena and their signature should have a…

Vaporization Characteristics of Ethanol Droplets: Influence of the Environment Humidity

2011

The study of the gasification of a droplet via vaporization, which involves heat, mass and momentum transfer processes in gas and liquid phases, and their coupling at the droplet interface, is necessary for better understanding and modeling of complex spray and mixture formation issues. A detailed description of the vaporization of an isolated droplet has been realized in this experimental study aimed at investigating the impact of the water vapor contained in the surrounding gas on the evaporation of an ethanol droplet. The experimental set-up consists of a heated chamber with a cross quartz fibers configuration as droplet support. An ethanol droplet is located at the intersection of the c…

The importance of fracture-healing on the deformation of fluid-filled layered systems

2014

International audience; Understanding the fracturingehealingerefracturing cycle is a fundamental part of studying the deformation dynamics and the permeability evolution of rock systems. Previous studies, however, have not examined the influence of healing i.e. fracture-closure through vein formation and the mechanical properties of the " healed " fractures (veins) on the rock deformation. We present results from a two-dimensional coupled hydro-mechanical model which simulates large time and spatial scale dynamic fracturing and healing of a porous medium under the influence of gravity, tectonic stretching and elevated fluid pressures. Our results show that healing decreases the local porosi…

Influence of bed roughness on flow and turbulence structure around a partially-buried, isolated freshwater mussel

2023

The present study uses eddy-resolving numerical simulations to investigate how bed roughness affects flow and turbulence structure around an isolated, partially-buried mussel (Unio elongatulus) aligned with the incoming flow. The rough-bed simulations resolve the flow past the exposed part of a gravel bed, whose surface is obtained from a laboratory experiment that also provides some additional data for validation of the numerical model. Results are also discussed for the limiting case of a horizontal smooth bed. Additionally, the effects of varying the level of burial of the mussel inside the substrate and the discharge through the two mussel siphons are investigated via a set of simulatio…

2016

Recent gas flux measurements have shown that Strombolian explosions are often followed by periods of elevated flux, or “gas codas,” with durations of order a minute. Here we present UV camera data from 200 events recorded at Stromboli volcano to constrain the nature of these codas for the first time, providing estimates for combined explosion plus coda SO2 masses of ≈18–225 kg. Numerical simulations of gas slug ascent show that substantial proportions of the initial gas mass can be distributed into a train of “daughter bubbles” released from the base of the slug, which we suggest, generate the codas, on bursting at the surface. This process could also cause transitioning of slugs into cap b…

A boundary condition for arbitrary shaped inlets in lattice-Boltzmann simulations

2009

We introduce a mass-flux-based inlet boundary condition for the lattice-Boltzmann method. The proposed boundary condition requires minimal amount of boundary data, it produces a steady-state velocity field which is accurate close to the inlet even for arbitrary inlet geometries, and yet it is simple to implement. We demonstrate its capability for both simple and complex inlet geometries by numerical experiments. For simple inlet geometries, we show that the boundary condition provides very accurate inlet velocities when Re less than or similar to 1. Even with moderate Reynolds number, the inlet velocities are accurate for practical purposes. Furthermore, the potential of our boundary condit…

On the Modeling of Transcatheter Therapies for the Aortic and Mitral Valves: A Review

2022

Transcatheter aortic valve replacement (TAVR) has become a milestone for the management of aortic stenosis in a growing number of patients who are unfavorable candidates for surgery. With the new generation of transcatheter heart valves (THV), the feasibility of transcatheter mitral valve replacement (TMVR) for degenerated mitral bioprostheses and failed annuloplasty rings has been demonstrated. In this setting, computational simulations are modernizing the preoperative planning of transcatheter heart valve interventions by predicting the outcome of the bioprosthesis interaction with the human host in a patient-specific fashion. However, computational modeling needs to carry out increasingl…

Characterization of gas flow through low-permeability claystone: laboratory experiments and two-phase flow analyses

2014

For the characterization of gas migration through a low-permeability clay host rock for deep underground repositories, a comprehensive understanding of the relevant phenomena of gas and fluid flow through low-permeability clay is required. The National Cooperative for the Disposal of Radioactive Waste (Nagra) in Switzerland has developed a comprehensive programme to characterize gas flow in low-permeability Opalinus Clay through laboratory tests and detailed numerical analyses for developing appropriate constitutive models. Laboratory tests were performed on cores by two different laboratories, the Laboratory for Soil Mechanics at EPFL and the Department of Geotechnical Engineering and Geos…