The Experts below are selected from a list of 36 Experts worldwide ranked by ideXlab platform
Giovanni Macedonio - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear phenomena in fluids with temperature-dependent viscosity: An hysteresis model for magma Flow in Conduits
Geophysical Research Letters, 2002Co-Authors: Antonio Costa, Giovanni MacedonioAbstract:Magma viscosity is strongly temperature-dependent. When hot magma Flows in a conduit, heat is lost through the walls and the temperature decreases along the Flow causing a viscosity increase. For particular values of the controlling parameters the steady-Flow regime in a conduit shows two stable solutions belonging either to the slow or to the fast branch. As a consequence, this system may show an hysteresis effect, and the transition between the two branches can occur quickly when certain critical points are reached. in this paper we describe a model to study the relation between the pressure at the inlet and the volumetric magma Flow rate in a conduit. We apply this model to explain an hysteric jump observed during the dome growth at Soufri\`ere Hills volcano (Montserrat), and described by Melnik and Sparks [1999] using a different model.
James A Cherry - One of the best experts on this subject based on the ideXlab platform.
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Assessing the Flow regime in a contaminated fractured and karstic dolostone aquifer supplying municipal water
Journal of Hydrology, 2011Co-Authors: Jérôme Perrin, Beth L Parker, James A CherryAbstract:The Silurian dolostone bedrock in Ontario, Canada, is a broad 400 km long swath northward from Niagara Falls through the Bruce Peninsula that represents an important water source for municipal, industrial, and agricultural uses. Where the Quaternary overburden is thin or absent, karst is common. This study concerns an urban area where the dolostone aquifer is 100 m thick beneath up to 50 m thick Quaternary deposits and where karst features identified by borehole information are common. Hydraulic tests show moderate to large bulk rock hydraulic conductivity and rock core tests indicate much smaller matrix hydraulic conductivity than the bulk rock values. Therefore, the aquifer is essentially a dual permeability, fully saturated system in which Conduits occur within a network of ubiquitous extensive, horizontally- and vertically-interconnected fractures. Karst features are concentrated in a thin zone at the top-of-rock, likely representing former epikarst, and also in a thicker zone in the middle of the aquifer. Some pumping test results and large yields of some municipal wells are consistent with conduit occurrences. However, atmospheric tritium, distributed-source contamination (Cl−, View the MathML source), and a point-source pesticide plume (metolachlor) show detailed concentration distributions lacking influence of Flow in Conduits. Detailed hydraulic head profiles also show no influence of conduit Flow. This study shows that when designing monitoring networks for groundwater quality and source water protection in similar contexts, locating Conduits is not necessary because contaminant distributions are governed by the combined influences of the rock matrix, fractures and Conduits, the hydraulic boundary conditions, and the interconnected fracture network with only minimal conduit effects. Prior to glaciations, an integrated karstic aquifer could develop with Flow controlled by Conduits; however, this original, converging Flow system became non-functional when the Quaternary sediments drastically modified the boundary hydrologic conditions and the head distribution.
Herbert E Huppert - One of the best experts on this subject based on the ideXlab platform.
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compressible vapour Flow in Conduits and fractures
Journal of Fluid Mechanics, 2016Co-Authors: Herbert E Huppert, Stephen R J SparksAbstract:We consider the steady Flow of a viscous compressible gas through an axisymmetric or two-dimensional porous medium whose properties in the direction of the Flow are sufficiently slowly varying. The study is partly motivated by a number of different applications in the Earth sciences, including the release of magmatic volatiles from a magma chamber beneath an active volcano and the discharge of geothermal fluids. The results are also relevant to evaluating the consequences of an accidental release of carbon dioxide from a storage reservoir within the Earth, as might happen at a carbon capture and storage (CCS) site. We consider both slow, thermally equilibrated, Flows and fast, adiabatic Flows. Because the Flow is compressible, it is the mass (and not the volume) flux which is conserved along the Flow. We determine this constant mass flux and the velocity and pressure fields, both of which vary with position along the Flow, as a function of all the physical parameters. We find that the resultant pressure gradient in the medium is largest at the far, low-pressure end of the conduit because the velocity is largest at that end due to the smallest density being associated with the smallest pressures. This means that the pressure in the permeable conduit is always larger than the linear pressure distribution which joins the given pressures at depth and at the surface, as would be the situation if the Flow were incompressible. The detailed pressure distribution is shown to depend on the variation with depth of the quantity , where is the dynamic viscosity of the vapour, is the external temperature, the permeability and the cross-sectional area of the conduit. The resultant mass flux is determined to be proportional to the mean along the Flow of . We present two numerical illustrations of the results.
Antonio Costa - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear phenomena in fluids with temperature-dependent viscosity: An hysteresis model for magma Flow in Conduits
Geophysical Research Letters, 2002Co-Authors: Antonio Costa, Giovanni MacedonioAbstract:Magma viscosity is strongly temperature-dependent. When hot magma Flows in a conduit, heat is lost through the walls and the temperature decreases along the Flow causing a viscosity increase. For particular values of the controlling parameters the steady-Flow regime in a conduit shows two stable solutions belonging either to the slow or to the fast branch. As a consequence, this system may show an hysteresis effect, and the transition between the two branches can occur quickly when certain critical points are reached. in this paper we describe a model to study the relation between the pressure at the inlet and the volumetric magma Flow rate in a conduit. We apply this model to explain an hysteric jump observed during the dome growth at Soufri\`ere Hills volcano (Montserrat), and described by Melnik and Sparks [1999] using a different model.
Stephen R J Sparks - One of the best experts on this subject based on the ideXlab platform.
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compressible vapour Flow in Conduits and fractures
Journal of Fluid Mechanics, 2016Co-Authors: Herbert E Huppert, Stephen R J SparksAbstract:We consider the steady Flow of a viscous compressible gas through an axisymmetric or two-dimensional porous medium whose properties in the direction of the Flow are sufficiently slowly varying. The study is partly motivated by a number of different applications in the Earth sciences, including the release of magmatic volatiles from a magma chamber beneath an active volcano and the discharge of geothermal fluids. The results are also relevant to evaluating the consequences of an accidental release of carbon dioxide from a storage reservoir within the Earth, as might happen at a carbon capture and storage (CCS) site. We consider both slow, thermally equilibrated, Flows and fast, adiabatic Flows. Because the Flow is compressible, it is the mass (and not the volume) flux which is conserved along the Flow. We determine this constant mass flux and the velocity and pressure fields, both of which vary with position along the Flow, as a function of all the physical parameters. We find that the resultant pressure gradient in the medium is largest at the far, low-pressure end of the conduit because the velocity is largest at that end due to the smallest density being associated with the smallest pressures. This means that the pressure in the permeable conduit is always larger than the linear pressure distribution which joins the given pressures at depth and at the surface, as would be the situation if the Flow were incompressible. The detailed pressure distribution is shown to depend on the variation with depth of the quantity , where is the dynamic viscosity of the vapour, is the external temperature, the permeability and the cross-sectional area of the conduit. The resultant mass flux is determined to be proportional to the mean along the Flow of . We present two numerical illustrations of the results.