Letteratura scientifica selezionata sul tema "Environmental fluid mechanics"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Consulta la lista di attuali articoli, libri, tesi, atti di convegni e altre fonti scientifiche attinenti al tema "Environmental fluid mechanics".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Articoli di riviste sul tema "Environmental fluid mechanics"
1
Rubin,, H., J. Atkinson, e B. Sanderson,. "Environmental Fluid Mechanics". Applied Mechanics Reviews 55, n. 3 (1 maggio 2002): B59—B60. http://dx.doi.org/10.1115/1.1470688.
Testo completo
2
Marion, Andrea. "Fluid mechanics of environmental interfaces". Journal of Hydraulic Research 52, n. 4 (4 luglio 2014): 580–81. http://dx.doi.org/10.1080/00221686.2014.945500.
Testo completo
3
Hunt, J. C. R. "Industrial and Environmental Fluid Mechanics". Annual Review of Fluid Mechanics 23, n. 1 (gennaio 1991): 1–42. http://dx.doi.org/10.1146/annurev.fl.23.010191.000245.
Testo completo
4
Kolditz,, O., e LA Glenn,. "Computational Methods in Environmental Fluid Mechanics". Applied Mechanics Reviews 55, n. 6 (16 ottobre 2002): B117—B118. http://dx.doi.org/10.1115/1.1508157.
Testo completo
5
Verzicco, R. "Computational Methods for Environmental Fluid Mechanics". European Journal of Mechanics - B/Fluids 21, n. 4 (gennaio 2002): 493–94. http://dx.doi.org/10.1016/s0997-7546(02)01194-9.
Testo completo
6
Chanson, Hubert, Fabian Bombardelli e Oscar Castro-Orgaz. "Environmental fluid mechanics in hydraulic engineering". Environmental Fluid Mechanics 20, n. 2 (6 marzo 2020): 227–32. http://dx.doi.org/10.1007/s10652-020-09739-5.
Testo completo
7
Grimshaw, R., e O. Phillips. "Environmental Stratified Flows. Topics in Environmental Fluid Mechanics, Vol. 3". Applied Mechanics Reviews 55, n. 5 (1 settembre 2002): B102—B103. http://dx.doi.org/10.1115/1.1497491.
Testo completo
8
Isaacson, Michael. "BASIC fluid mechanics". Canadian Journal of Civil Engineering 16, n. 2 (1 aprile 1989): 208. http://dx.doi.org/10.1139/l89-043.
Testo completo
9
Bennett, Gary F. "Fluid mechanics for industrial safety and environmental protection". Journal of Hazardous Materials 48, n. 1-3 (giugno 1996): 265–66. http://dx.doi.org/10.1016/s0304-3894(96)90010-2.
Testo completo
10
Tan, Lai-wai, e Vincent H. Chu. "Lagrangian block hydrodynamics for environmental fluid mechanics simulations". Journal of Hydrodynamics 22, S1 (ottobre 2010): 627–32. http://dx.doi.org/10.1016/s1001-6058(10)60009-1.
Testo completoTesi sul tema "Environmental fluid mechanics"
1
Szulczewski, Michael Lawrence. "The subsurface fluid mechanics of geologic carbon dioxide storage". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82834.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 157-168).
In carbon capture and storage (CCS), CO₂ is captured at power plants and then injected into deep geologic reservoirs for long-term storage. While CCS may be critical for the continued use of fossil fuels in a carbon-constrained world, the subsurface behavior of CO₂ remains poorly understood, which has contributed to the absence of government policy to implement CCS. In this Thesis, we use simulations, experiments, and theory to clarify the fluid mechanics of CO₂ storage, with the goal of informing two practical questions. The first question is, how much CO₂ can be stored in the United States? This question is important to clarify the role of CCS among the portfolio of other climate-change mitigation options, such as renewable energy and reduced energy consumption. To address this question, we develop models of CO₂ injection and the post-injection migration, and apply them to several reservoirs in the US. We use the models to calculate the total amount of CO₂ that can be stored in these reservoirs without hydraulically fracturing the caprock or allowing the CO₂ to migrate to a major leakage pathway. We find that the US has sufficient storage capacity to stabilize emissions at the current rates for at least 100 years. The second question is, what are the long-term dissolution rates of CO₂ into the ambient groundwater? This question is important because dissolution mitigates the risk of CO₂ leakage to shallower formations or the surface. We address this question for storage in structural and stratigraphic traps, which are promising locations in a reservoir for injection and will likely be the first sites of large-scale CCS deployment. We describe several mechanisms of CO₂ dissolution in these traps and develop models to predict the dissolution rates. We apply the models to relevant subsurface conditions and find that dissolution rates vary widely depending on the reservoir properties, but that thick reservoirs with high permeabilities could potentially dissolve hundreds of megatons of CO₂ in tens of years.
by Michael Lawrence Szulczewski.
Ph.D.
2
Laubie, Hadrien Hyacinthe. "Linear elastic fracture mechanics in anisotropic solids : application to fluid-driven crack propagation". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82838.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 167-169).
Fracture mechanics is a field of continuum mechanics with the objective to predict how cracks initiate and propagate in solids. It has a wide domain of application. While aerospace engineers want to make sure a defect in a structure will not grow and possibly lead to failure, petroleum engineers try to increase the permeability of gas shale rocks by fracturing it. In this context, we introduce some elements of linear elastic fracture mechanics in anisotropic solids. Notably, a special attention is paid to transverse isotropy, often used to model rocks but also some piezoelectric materials or fiber-reinforced composites. We focus on brittle materials, that is, we consider only elastic deformations; we thus ignore dissipative phenomena other than the one associated with the creation of crack surface. This thesis aims at understanding and predicting how pressurized cracks propagate in anisotropic brittle solids, in the framework of linear elastic fracture mechanics. The elastic coefficients relevant to the study of a pressurized crack in such materials are identified. Interestingly, they are directly related to quantities easily measured in a lab at the macroscopic scale through indentation tests and acoustic measurements. As an application, the fluid-driven crack problem is addressed. It is shown that the classical tools of the isotropic fluid-driven crack model remain valid in anisotropy, provided the appropriate elastic constants are used. We introduce the concept of crack-shape adaptability: the ability of three-dimensional cracks to shape with the elastic content. This ability could be ruled by three criteria herein introduced. The first one is based on the maximum dissipation principle. The second one is based on Irwin's theory of fracture and the concept of stress intensity factors. As for the third one, it is based on Griffith's energetic theory. While the first criterion predicts that circular cracks are more favorable, the others predict that elliptical shapes are more likely to be seen. This thesis could be valuable in the context of the stimulation of unconventional oil and gas from organic-rich shale.
by Hadrien Hyacinthe Laubie.
S.M.
3
Khan, Muhammad Ahsan. "CFD Applications for Wave Energy Conversion Devices (MoonWEC) and Turbulent Fountains for Environmental Fluid Mechanics". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Cerca il testo completoAbstract (sommario):
This thesis is based on two studies that are related to floating wave energy conversion (WEC) devices and turbulent fountains. The ability of the open-source CFD software OpenFOAM® has been studied to simulate these phenomena. The CFD model has been compared with the physical experimental results.
The first study presents a model of a WEC device, called MoonWEC, which is patented by the University of Bologna. The CFD model of the MoonWEC under the action of waves has been simulated using OpenFOAM and the results are promising. The reliability of the CFD model is confirmed by the laboratory experiments, conducted at the University of Bologna, for which a small-scale prototype of the MoonWEC was made from wood and brass.
The second part of the thesis is related to the turbulent fountains which are formed when a heavier source fluid is injected upward into a lighter ambient fluid, or else a lighter source fluid is injected downward into a heavier ambient fluid. For this study, the first case is considered for laboratory experiments and the corresponding CFD model. The vertical releases of the source fluids into a quiescent, uniform ambient fluid, from a circular source, were studied with different densities in the laboratory experiments, conducted at the University of Parma. The CFD model has been set up for these experiments. Favourable results have been observed from the OpenFOAM simulations for the turbulent fountains as well, indicating that it can be a reliable tool for the simulation of such phenomena.
4
Rodríguez, Buño Mariana. "Near and far field models of external fluid mechanics of Ocean Thermal Energy Conversion (OTEC) power plants". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79495.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 126-130).
The world is facing the challenge of finding new renewable sources of energy - first, in response to fossil fuel reserve depletion, and second, to reduce greenhouse gas emissions. Ocean Thermal Energy Conversion (OTEC) can provide renewable energy by making use of the temperature difference between the surface ocean and deep ocean water in a Rankine cycle. An OTEC plant pumps huge volumes of water from the surface and nearly 1 km depth, and releases it at an intermediate depth. The effects of this enormous flux are crucial to understand since disruption of the ambient temperature stratification can affect the efficiency of the plant itself and of adjacent plants. This thesis aims to study the external fluid mechanics of offshore OTEC power plants, to assess their environmental impact and to help analyze whether OTEC plants can provide a sustainable source of energy. Although there has been interest in OTEC for several decades, so far primarily physical and analytical models have been developed. In this study numerical models are developed to model OTEC operating plants: integral models for the near and intermediate field and a large-scale ocean general circulation model. Two strategies in modeling OTEC plant discharge are used to analyze plume dynamics: the "Brute Force" approach, in which a circulation model, MITgcm, computes the near, intermediate and far field mixing; and the "Distributed Sources and Sinks" approach, in which the near and intermediate field are represented in the circulation model by sources and sinks of mass computed by integral models. This study concludes that the Brute Force modeling strategy is highly computationally demanding and sometimes inaccurate. Such simulations are very sensitive to model resolution and may require the use of unrealistic model parameters. The Distributed Sources and Sinks approach was found to be capable of modeling the plume dynamics accurately. This method can be applied to the study of adjacent OTEC power plant interaction, redistribution of nutrients, and propagation of contaminants.
by Mariana Rodríguez Buño.
S.M.
5
Jain, Antone Kumar. "Preferential mode of gas invasion in sediments : grain-scale model of coupled multiphase fluid flow and sediment mechanics". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51625.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Includes bibliographical references (p. 67-79).
We present a discrete element model for simulating, at the grain scale, gas migration in brine-saturated deformable media. We rigorously account for the presence of two fluids in the pore space by incorporating forces on grains due to pore fluid pressures, and surface tension between fluids. This model, which couples multiphase fluid flow with sediment mechanics, permits investigating the upward migration of gas through a brine-filled sediment column. We elucidate the ways in which gas migration may take place: (1) by capillary invasion in a rigid-like medium; and (2) by initiation and propagation of a fracture. We find that grain size is the main factor controlling the mode of gas transport in the sediment, and show that coarse-grain sediments favor capillary invasion, whereas fracturing dominates in fine-grain media. The results have important implications for understanding vent sites and pockmarks in the ocean floor, deep sub-seabed storage of carbon dioxide, and gas hydrate accumulations in ocean sediments and permafrost regions. Our results predict that, in fine sediments, hydrate will likely form in veins following a fracture-network pattern. In coarse sediments, the buoyant methane gas is likely to invade the pore space more uniformly, in a process akin to invasion percolation, and the overall pore occupancy is likely to be much higher than for a fracture-dominated regime. These implications are consistent with laboratory experiments and field observations of methane hydrates in natural systems.
by Antone Kumar Jain.
S.M.
6
Stipcich, Goran. "High-order methods for computational fluid dynamics". Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7764.
Testo completoAbstract (sommario):
2010/2011In the past two decades, the growing interest in the study of fluid flows involving discontinuities, such as shocks or high gradients, where a quadratic-convergent method may not provide a satisfactory solution, gave a notable impulse to the employment of high-order techniques. The present dissertation comprises the analysis and numerical testing of two high-order methods. The first one, belonging to the discontinuous finite-element class, is the discontinuous control-volume/finite-element method (DCVFEM) for the advection/ diffusion equation. The second method refers to the high-order finite-difference class, and is the mixed weighted non-oscillatory scheme (MWCS) for the solution of the compressible Euler equations. The methods are described from a formal point of view, a Fourier analysis is used to assess the dispersion and dissipation errors, and numerical simulations are conducted to confirm the theoretical results.
XXIV Ciclo
1980
7
Kumar, Ashish R. "Dust Control Examination using Computational Fluid Dynamics Modeling and Laboratory Testing of Vortecone and Impingement Screen Filters". UKnowledge, 2018. https://uknowledge.uky.edu/mng_etds/44.
Testo completoAbstract (sommario):
Heavy industries, such as mining, generate dust in quantities that present an occupational health hazard. Prolonged exposure to the respirable dust has been found to result in many irreversible occupational ailments in thousands of miners. In underground mining applications, a variety of scrubbing systems are used to remove dust near the zones of generation. However, the wire-mesh type fibrous screens in the flooded-bed dust scrubbers used on continuous miners, are prone to clogging due to the accumulation of dust particles. This clogging results in a reduced capture efficiency and a higher exposure to the personnel. This research establishes the Vortecone, an inertial wet scrubber system, as a suitable alternative to the existing filters. The Vortecone accelerates its inlet fluids into a rapid circulatory motion into a vortex chamber, preferentially moving the heavier particles towards the impermeable surface to be trapped by the circulating water film. Vortecones are used on automobile painting lines and capture over-sprayed paint particles with cleaning efficacies exceeding 99 % while requiring only infrequent maintenance. The existing design of the Vortecone could also be altered to control the flow patterns.
This dissertation presents detailed computational fluid dynamics (CFD) models to describe air flow patterns in the Vortecone in steady and transient states. Multi-phase spray models were generated to simulate injection of water into the Vortecone. The volume of fraction (VOF) approach was adopted to mimic the air-water interface. The Lagrangian particle tracking method was used to model particle capture on the interface described by the VOF. The CFD models indicate excellent cleaning efficacies, especially of larger particles. Laboratory experiments with optical measurements of aerosols in a reduced scale model of the Vortecone validate the computer models. These experiments which were performed on dust samples with particle sizes 0.3 μm and above, show that the Vortecone captures 90 % particles by mass exceeding about 5.20 and 3.20 μm at air flows of 0.28 m3/s (600 cfm) and 0.38 m3/s (800 cfm), respectively. The development of detailed large eddy simulations (LES) of air flow in the Vortecone provides a novel contribution to research by better resolving the flow patterns.
An impactor-type, self-cleaning, non-clogging impingement screen system was designed as a substitute for conventional screens used in continuous miners. The screen could further be used as an efficient dust capturing mechanism with a demister in general mining applications. CFD models and laboratory experiments are presented to establish the cleaning efficacies of the system. Laboratory experiments to investigate the cleaning efficiency of a fibrous-type conventional screen is also discussed. The parameter, filter selection factor, is proposed to compare the performance of the three systems (Vortecone, fibrous screen, and impingement screen) under similar flows. The Vortecone has been found to be the most efficient dust-cleansing system, although it is the most power intensive fillter. The impingement screen shows a similar cleaning efficiency and a much higher availability compared to the conventional fibrous screen. Because of its minimal maintenance requirement, the impingement screen shows significant promise in dust-control applications in mining.
8
Golfier, Fabrice. "Transport multi-échelle en milieu poreux : vers un couplage de l'hydrodynamique aux processus biophysico-chimiques". Habilitation à diriger des recherches, Institut National Polytechnique de Lorraine - INPL, 2011. http://tel.archives-ouvertes.fr/tel-00648924.
Testo completoAbstract (sommario):
Mes différentes activités de recherche qui s'insèrent dans une problématique axée autour du transport multi-échelle en milieu poreux sont détaillées ici au travers de 3 volets: (1) Influence des hétérogénéités sur les processus de transfert (2) Prise en compte des effets de couplage en transport réactif (3) Impact des processus biologiques sur l'hydrodynamique et le transport Un survol des défis qui restent à surmonter et des perspectives à venir de ce travail de recherche concluent le document.
9
Roman, Federico. "Large eddy simulation tool for environmental and industrial processes". Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3210.
Testo completoAbstract (sommario):
2007/2008Computational Fluid Dynamics (CFD) is an established tool for consulting and for basic research in fluid mechanics. CFD is required to provide information where analytical approaches or experiments would be impossible or too expensive. Most of the flows of engineering interest are turbulent. Turbulence is an unresolved problem of classical physics, because of the non linearity of the fluid motion equations. At the moment the only way to face them is numerically. Turbulence is composed of eddies in a broad range of size. To solve numerically the Navier-Stokes equations, the equations set that governs the fluid motion, a very fine grid is necessary in order to catch also the smallest eddies. The computational cost increases as Re3 (Re = ul/ is the Reynolds number with u and l an inertial velocity and length scales and the kinematic viscosity). Real life problems are characterized by very large Reynolds numbers and the consequent computational cost is enormous. So the direct solutions of Navier-Stokes equations (DNS) is not feasible. In many applications it is not necessary to solve all the eddies, it can be sufficient to supply the effects of unresolved scale to the flow. In Large Eddy Simulation (LES) most of the scales of motion are directly solved, in particular all the large energy carrying scales. These scales are influenced by the boundaries and they are strongly anisotropic. The smaller and dissipative scales must be modeled, but these scales loosing memory of the boundary conditions are more isotropic and hence formulating a general model that accounts for their effect is relatively easier. Large Eddy Simulation is a prospective tool for investigation in real life problems, in particular when high detailed analysis is required. This is the case for many industrial and environmental processes. For example, acoustic problems due to hydrodynamic noise are governed over a range of large scales which are easily reproduced by LES solution. However in these types of flows many difficulties arise also for LES. In general these flows are characterized by high Reynolds number. Wall-bounded flow at high Re requires high computational cost because LES is constrained to be DNS-like. Besides complex geometries are often involved. Structured or Unstructured body-fitted grid can be very hard to made, moreover unstructured grid can be expensive and not suited for LES. Scope of this thesis is to develop tools to apply LES to such configurations in order to make numerical simulation more adaptable to real life problems. In particular to deal with complex geometry an Immersed Boundary Methodology has been developed for curvilinear coordinates. The method has been applied to several test cases with good results. Then this methodology has been extended to high Reynolds number flows through the use of a wall model. In order to work on anisotropic grid, typical in sea coastal domain, a modified Smagorisky model has been proposed. Finally particle dispersion has been considered in stratified environmental flow. These tools has been applied to an industrial and to an environmental problem with good results.
La fluidodinamica computazionale (CFD) ´e uno strumento affermato per le consulenze e per la ricerca di base nella meccanica dei fluidi. Alla CFD ´e richiesto di fornire informazioni quando approcci analitici o sperimentali sarebbero impossibili o troppo costosi. La maggior parte dei flussi di interesse ingegneristico ´e di tipo turbolento. La turbolenza ´e uno dei problemi irrisolti della fisica classica, ci´o ´e dovuto alla non linearit´a delle equazioni che governano il moto dei fluidi. Al momento l’unico modo per affrontarle ´e numericamente. La turbolenza si compone di vortici di diverse dimensioni. Per risolvere numericamente le equazioni di Navier-Stokes, le equazioni che governano il moto dei fluidi, una griglia molto fine ´e necessaria al fine di simulare propriamente anche i vortici di scala pi´u piccola. Il costo computazionale cresce come Re3 (Re = ul/ ´e il numero di Reynolds, con u e l una velocit´a ed una lunghezza scala caratteristici e la viscosit´a cinematica). I problemi reali sono caratterizzati da numeri di Reynolds altissimi e conseguentemente il costo computazionale di queste simulazioni ´e enorme. Per questo motivo la soluzione diretta delle equazioni di Navier-Stokes (DNS) non ´e possibile. In molte applicazioni non ´e necessario risolvere tutte le scale dei vortici, pu´o essere sufficiente fornire l’effetto delle scale non risolte al flusso. Nella Large Eddy Simulation gran parte delle scale di vortici ´e direttamente risolta, in particolare le larghe scale energetiche. Queste scale sono influenzate dalle condizioni al contorno e sono fortemente anisotrope. Le scale piccole e dissipative devono essere modellate, ma queste scale perdendo memoria delle condizioni al contorno sono generalmente isotrope ed un modello per riprodurre il loro effetto risulta semplice. La LES ´e uno strumento d’avanguardia per lo studio di flussi realistici, in particolare risulta molto potente quando vengono richieste analisi dettagliate del moto. Questo ´e il caso di molti problemi in campo industriale ed ambientale. Per esempio problemi acustici dovuti a rumore idrodinamico sono governati dalle grandi scale che nella LES sono facilmente riprodotte. Comunque anche per la LES sorgono molte difficolt´a nel affrontare questi problemi. Generalmente questi flussi sono caratterizzati da alti numeri di Reynolds. Flussi di parete ad alti Re richiedono un costo computazionale elevatissimo e alla fine la LES deve soddisfare a requisiti tipici della DNS. Inoltre spesso questi flussi sono caratterizzati da geometrie complesse. Griglie strutturate o non strutturate che si adattano alle geometrie possono essere molto difficili da sviluppare, inoltre le griglie non strutturate possono essere molto costose e non particolarmente adatte alla LES. Lo scopo di questa tesi ´e di sviluppare degli strumenti atti a rendere efficiente l’applicazione della LES a flussi realistici. In particolare per affrontare le geometrie complesse ´e stata sviluppata una metodologia Immersed Boundary per coordinate curvilinee. Il metodo ´e stato provato su diversi casi con buoni risultati. La metodologia ´e stata quindi estesa al caso di flussi ad alto numero di Reynolds tramite lo sviluppo di un modello parete. ´E stato quindi sviluppato un modello modificato di Smagorinsky per lavorare con griglie fortemente anisotrope, tipiche per flussi in ambito marino costiero. Infine ´e stata studiata la dispersione di particelle in flussi ambientali stratificati. Gli strumenti sviluppati sono stati quindi applicati ad un problema industriale ed ad uno ambientale con ottimi risultati.
XXI Ciclo
1976
10
Vukicevic, Marija. "Vortex formation behind movable leaflet: experimental and numerical studies". Doctoral thesis, Università degli studi di Trieste, 2011. http://hdl.handle.net/10077/5368.
Testo completoAbstract (sommario):
2009/2010Fluid structure interaction (FSI) is one of fundamental phenomena encountered everywhere in nature or in industrial systems as well as one of the most studied and the most challenging topics in the fluid mechanics. Its research presents the core objective of this dissertation, along with experimental study of artificial heart devices. Better understanding of FSI could turn the still unexploited phenomenon into a powerful tool for resolving wealthy of multi-physics problems. Recently computational fluid dynamics community has been putting enormous efforts to uncover, make clear and answer yet numerous issues related to this developing topic. In addition, the FSI is often followed by the vortex formation, one more phenomena that could be both powerful driving force as well as distracting, disturbing occurrence. Consequently, this dissertation will begin with addressing some open issues related to the fluid-structure interaction associated with the simple system made of movable rigid leaflet and an unsteady viscous fluid flow. Such two-dimensional model, even if it appears extremely simple, is able to produce fairly rich flow features which deserve careful analytical and accurate numerical solution. Thus, we have performed a significant number of numerical experiments with the objective to uncover the role of the structure inertia in the overall behavior of the fluid-leaflet system, under the different flow recurrences. For that purpose, we have constructed a strong-coupling code and resolved the fluid and structure dynamics simultaneously, paying particular care of solution accuracy around the moving boundary. The complex problem of large fluid deformation in response to the rapid structure movements has been resolved by the time-dependent conformal mapping, exclusively developed for this specific physical arrangement. The numerical findings, even if theoretical in nature, allowed for the classification and characterization of body’s and fluid dynamics in functionality of different structure inertia and Strouhal numbers, which have been used as free parameters in all numerical experiments. The study is completed by a brief analysis of the more realistic system of actual prosthetic heart valves. Besides many problems that follow the performance of mechanical heart valve prosthesis, the complications related to the complex blood-leaflet interaction are a key factor. The intraventricular flow is characterized by large vortical structures, without significant turbulence, in a smooth circulatory pattern that, in presence of pathological conditions or mechanical devices, could be disturbed. Thus, among the criteria for the assessment of mitral valve functionality and mechanical valve design are the proper vortical features inside the left ventricle. Until nowadays the standard mechanical valves, designed originally for the aortic replacement and without exceptions symmetrical, have never satisfied the regularity of natural vortical dynamics. Thus, we have been motivated to investigate the flow features downstream of asymmetrical prototypes, exclusively designed for the mitral replacement with attempt to better mimic the natural intraventricular flow. Experimental outcomes allowed for preliminary conclusions that the break of symmetry in the novel prosthesis creates the asymmetrical vortical flow in the left ventricle, which is more similar to the natural one, although the concept introduced by this prototype has to undergo deeper testing and careful improvements before querying in the real hearts.
XXIII Ciclo
1982
Libri sul tema "Environmental fluid mechanics"
1
F, Atkinson Joseph, a cura di. Environmental fluid mechanics. New York: Marcel Dekker, 2001.
Cerca il testo completo
2
Mihailovic, Dragutin T. Advances in environmental fluid mechanics. Singapore: World Scientific, 2010.
Cerca il testo completo
3
Carlo, Gualtieri, e Mihailovic Dragutin T, a cura di. Fluid mechanics of environmental interfaces. London: Taylor & Francis, 2008.
Cerca il testo completo
4
Carlo, Gualtieri, e Mihailovic Dragutin T, a cura di. Fluid mechanics of environmental interfaces. London: Taylor & Francis, 2008.
Cerca il testo completo
5
Kolditz, Olaf. Computational Methods in Environmental Fluid Mechanics. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-04761-3.
Testo completo
6
H, Shen Hayley, a cura di. Environmental fluid mechanics: Theories and applications. Reston, Va: American Society of Civil Engineers, 2002.
Cerca il testo completo
7
Kolditz, Olaf. Computational Methods in Environmental Fluid Mechanics. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002.
Cerca il testo completo
8
name, No. Environmental fluid mechanics: Theories and applications. Reston, VA: American Society of Civil Engineers, 2003.
Cerca il testo completo
9
Shalaby, Ahlam I. Fluid Mechanics for Civil and Environmental Engineers. Boca Raton : Taylor & Francis a CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa, plc, [2018]: CRC Press, 2018. http://dx.doi.org/10.1201/9781315156637.
Testo completo
10
Fannelöp, Torstein K. Fluid mechanics for industrial safety and environmental protection. Amsterdam: Elsevier, 1994.
Cerca il testo completoCapitoli di libri sul tema "Environmental fluid mechanics"
1
Kaye, Nigel B., Abdul A. Khan e Firat Y. Testik. "Environmental Fluid Mechanics". In Handbook of Environmental Engineering, 303–32. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2018. http://dx.doi.org/10.1002/9781119304418.ch10.
Testo completo
2
Jirka, G. H. "Environmental Fluid Mechanics". In Environmental Applications of Mechanics and Computer Science, 49–98. Vienna: Springer Vienna, 1999. http://dx.doi.org/10.1007/978-3-7091-2492-5_4.
Testo completo
3
Romero-Guzmán, Elizabeth Teresita, Lázaro Raymundo Reyes-Gutiérrez e Jaime Lázaro Klapp-Escribano. "Environmental Fluid Dynamics". In Experimental and Computational Fluid Mechanics, 349–58. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-00116-6_30.
Testo completo
4
McPherson, Malcolm J. "Introduction of fluid mechanics". In Subsurface Ventilation and Environmental Engineering, 15–49. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1550-6_2.
Testo completo
5
Dyke, Philip. "Environmental Impact Modelling". In Topics in Environmental Fluid Mechanics, 173–202. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4757-4786-7_7.
Testo completo
6
Mathias, Simon A. "Basic Principles of Fluid Mechanics". In Hydraulics, Hydrology and Environmental Engineering, 3–35. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-41973-7_1.
Testo completo
7
Shalaby, Ahlam I. "Fluid Statics". In Fluid Mechanics for Civil and Environmental Engineers, 115–299. Boca Raton : Taylor & Francis a CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa, plc, [2018]: CRC Press, 2018. http://dx.doi.org/10.1201/9781315156637-2.
Testo completo
8
Kolditz, Olaf. "Balance Equations of Fluid Mechanics". In Computational Methods in Environmental Fluid Mechanics, 3–28. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-04761-3_1.
Testo completo
9
Dyke, Philip. "The Modelling Process and Environmental Impact". In Topics in Environmental Fluid Mechanics, 5–16. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4757-4786-7_1.
Testo completo
10
Dyke, Philip. "Dynamic Balances". In Topics in Environmental Fluid Mechanics, 17–52. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4757-4786-7_2.
Testo completoAtti di convegni sul tema "Environmental fluid mechanics"
1
Redondo, J. M., A. Carrillo, M. Diez, J. Jorge e E. Sekula. "ENVIRONMENTAL PATTERNS AND INTERMITTENT CASCADES". In Topical Problems of Fluid Mechanics 2017. Institute of Thermomechanics, AS CR, v.v.i., 2017. http://dx.doi.org/10.14311/tpfm.2017.033.
Testo completo
2
Uhlíř, V., T. Bodnár e M. Caggio. "Numerical Assessment of Stratification Influence in Simple Algebraic Turbulence Model". In Topical Problems of Fluid Mechanics 2022. Institute of Thermomechanics of the Czech Academy of Sciences, 2022. http://dx.doi.org/10.14311/tpfm.2022.022.
Testo completoAbstract (sommario):
This paper presents rst few results obtained using a newly developed test code aimed at validation and cross-comparison of turbulence models to be applied in environmental flows. A simple code based on nite di erence discretization is constructed to solve steady flows of incompresible non-homogeneous (variable denstity) fluids. For the rst tests a simple algebraic turbulence model was implemented, containing stability function depending on the stratification via the gradient Richardson number. Numerical tests were performed in order to explore the capabilities of the new code and to get some insight into its behavior under di erent stratification. The two-dimensional simulations were performed using immersed boundary method for the flow over low smooth hill. The resulting flow fields are compared for selected Richarson numbers ranging from stable up to unstable strati cation conditions.
3
STETSON, K., E. THOMPSON, J. DONALDSON e L. SILER. "Laminar boundary layer stability experiments on a cone at Mach 8. IV- On unit Reynolds number and environmental effects". In 4th Joint Fluid Mechanics, Plasma Dynamics and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1986. http://dx.doi.org/10.2514/6.1986-1087.
Testo completo
4
Wang, Tao, Zhaohua Yin e Wenrui Hu. "On a combined measurement technique of PIV and shadowgraph in environmental fluid dynamics". In International Conference on Experimental Mechnics 2008 and Seventh Asian Conference on Experimental Mechanics, a cura di Xiaoyuan He, Huimin Xie e YiLan Kang. SPIE, 2008. http://dx.doi.org/10.1117/12.839070.
Testo completo
5
Gala, Deepen, Murtadha J. AlTammar e Mukul M. Sharma. "Field-Scale Modeling of Fracturing with Slickwater, N2, CO2 and Foams – A Fundamental Investigation". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0142.
Testo completoAbstract (sommario):
ABSTRACT Hydraulic fracturing is typically done with water-based, incompressible fracturing fluids. However, other fluids such as pure gases or foams are also used as driven by logistics or well productivity optimization. There are differences in fracture growth behavior amongst various fracturing fluids due to variability in properties such as viscosity, density, compressibility, leakoff, etc. Several laboratory experiments have recently been performed which indicated differences in breakdown pressure, fracture growth rate, complexity of the created fractures and amount of fracturing fluid leaked off into the formation. However, the laboratory results cannot be directly applied to the field without proper upscaling. In this work, we perform a field scale modeling of different fracturing fluids to provide more insights on how to design a fracturing job using non-water based fluids. We systematically study the role of wellbore volume, viscosity, compressibility, reservoir permeability, poroelasticity and magnitude of minimum horizontal stress on the fracture propagation behavior. It was found that poroelasticity effects are quite important for low viscosity fluids in micro-Darcy reservoirs. Also, when wellbore storage effects are considered, breakdown time is higher and breakdown pressure is lower for higher compressibility fluids. In low permeability reservoirs, an increase in fluid viscosity reduces the fracture length and increases width. In higher permeability reservoirs, an increase in viscosity reduces leakoff and thus increases both length and width. Low stress environments behave differently than high stress environments due to differences in fluid compressibility and stress/tensile strength ratio. A multi-cluster study of a single stage in a horizontal well is also performed for slickwater, gases (CO2 and N2) and foams (with different quality). The injection period and shut-in are both modeled and compared among the different fluid injection cases. INTRODUCTION Hydraulic fracturing treatments of oil and gas formations are mostly performed using slickwater, gelled water and hybrid fluids (Dejam et al. 2018). Many field applications, however, require minimizing the amount of water used in fracturing treatments due to water scarcity, environmental issues, and/or local regulations. In addition, using less water in fracturing can improve well productivity by reducing gel damage, relative hydrocarbon permeability damage, clay swelling and fines migration, and proppant embedment (AlTammar 2014). Alternatives to water-based fluids such as nitrogen, CO2, and foams are promising candidates for use as fracturing fluids.
6
Smalls, P. T., R. Villamor-Lora, J. T. Germaine e H. H. Einstein. "Joule Heating of Brine Saturated Berea Sandstone: Observations from DC Electric Current". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0832.
Testo completoAbstract (sommario):
ABSTRACT High-voltage electrical current can be utilized to increase rock permeability and can be a sustainable alternative to decrease water consumption associated with hydraulic fracturing. During previous applications of this technique, ion carriers, mainly brine water, evaporated as temperature increased during electrical resistive (joule) heating of the reservoir, limiting effectiveness of the technique. Understanding how electrical conductivity evolves as a function of applied electrical current is fundamental for developing methods to overcome previous limitations of the technique. In this study, we developed a first-of-its kind triaxial cell that allows one to apply electrical current, with temperature and pore pressure data collected during the joule heating process of a Berea Sandstone rock specimen. We investigated the relationships between pore fluid composition, pore pressure, and electrical conductivity evolution. The relationships between pore fluid composition, and joule heating evolution under variable electrical energy inputs are important to understand for analyzing the long-term effectiveness of electrical rock fracturing. INTRODUCTION Waterless permeability enhancement techniques including mechanical, gaseous, and electrical based methods have been previously investigated to address the environmental concerns associated with hydraulic fracturing (e.g., Gandossi 2013, Kumar et. al, 2017, Wang et. al, 2016). However, widespread adoption of these techniques has stalled due to limitations in stimulated reservoir volume, and environmental safety concerns associated with the exposure of hazardous gases as a fracturing fluid. Alternatively, electrical resistive heating has proven effective at stimulating petroleum reservoirs to increase production (e.g., Elder et. al, 1957, Rehman and Meribout, 2012). Waterless permeability enhancement techniques including mechanical, gaseous, and electrical based methods have been previously investigated to address the environmental concerns associated with hydraulic fracturing (e.g., Gandossi 2013, Kumar et. al, 2017, Wang et. al, 2016). However, widespread adoption of these techniques has stalled due to limitations in stimulated reservoir volume, and environmental safety concerns associated with the exposure of hazardous gases as a fracturing fluid. Alternatively, electrical resistive heating has proven effective at stimulating petroleum reservoirs to increase production (e.g., Elder et. al, 1957, Rehman and Meribout, 2012).
7
Mejía, C., J. Rueda e D. Roehl. "Numerical Modeling of Fluid-Driven Fractures in Permeable Media Using Symmetric Cohesive Elements". In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-1071.
Testo completoAbstract (sommario):
ABSTRACT: Hydraulic fracturing is one of the most widely used techniques adopted in the oil industry to enhance reservoir permeability. In traditional hydraulic fracture modeling, the numerical model simulates half of the fracture geometry by taking advantage of model symmetry. However, hydraulic fracture modeling in heterogeneous rock formations considering a fully coupled formulation can require significant computational effort, especially in 3D models. This work proposes a symmetric cohesive element to simulate fluid-driven fractures in permeable porous media. In this approach, the hydraulic fracture path coincides with the plane of symmetry of the fracture, allowing the simulation of only a quarter of the fracture geometry. The symmetric cohesive element is obtained by imposing suitable constraints on the displacement degrees of freedom. In addition, the hydromechanical properties are updated to induce symmetric hydraulic fracture propagation. The proposed technique is successfully compared against the traditional full model, demonstrating simulation accuracy with substantially reduced computational cost. The numerical results demonstrate the capability of the proposed approach to successfully simulate hydraulic fracturing under under K and propagation regimes. Finally, this approach is an attractive alternative to simulate field scale models considering heterogeneous permeable rock formations. 1. INTRODUCTION The oil and gas industry employs the hydraulic fracturing technique to enhance unconventional reservoir permeability. The fracturing process involves the high-pressure injection of fracturing fluid to create cracks inside the rock formation, facilitating the migration of trapped hydrocarbon. However, it can lead to geomechanical problems such as seismicity (Rutqvist et al., 2013). Therefore, a better understanding of the hydraulic fracturing behavior is essential to reduce the associated environmental risks. However, the numerical modeling of hydraulic fracturing requires a better understanding of the physical mechanisms and also the ability to build field-scale models (Searles et al., 2016). In the last decades, numerical models have been developed to simulate hydraulic fracturing problems with complex fracture geometry (J. Adachi et al., 2007). Recently, several authors developed fully coupled HM zero-thickness interface elements, which modeled longitudinal and transversal fluid flow inside the fracture (Ng & Small, 1997; Segura & Carol, 2008). A fully coupled interface element with cohesive law is adopted to model hydraulic fracture propagation in permeable porous media (Chen et al., 2009; Zielonka et al., 2014). The capability of this approach was verified through comparison with available analytical solutions (Carrier & Granet, 2012) and laboratory fracturing tests (Searles et al., 2016). However, accurate modeling of hydraulic fracturing requires refined mesh close to the fracture plane, which is computationally expensive for 3D field-scale models.
8
Punj, P. "Investigating the fluid-structure interaction of L-shaped pipe bends using machine learning". In Advanced Topics in Mechanics of Materials, Structures and Construction. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902592-25.
Testo completoAbstract (sommario):
Abstract. The fluid Structure interface is an important area of research for its challenges in fluid structure dynamics in understanding the effect of fluid on motion and deformation of structures. In the current study, we used the L-Shaped pipe bent and did a CFD simulation at the velocity inlet condition of the range 1-3 m/s with keeping adiabatic wall condition and environmental pressure at the outlet. The reason for choosing L-Shaped bent is that it creates a sharp change in the flow direction, which leads to complex vortices, turbulence and pressure distribution. It also puts a significant mechanical load on the structure due to this change in flow, resulting in a large structural deformation. The result of CFD simulation is used to do the structural simulations at different material types, lengths of both arms, keeping the diameter, angle and fillet radius of the bent at a constant value. The database created is then used as an input to the machine learning (ML) model to predict for an arbitrary material and at any length of the bent without doing all the simulations. The simulation results also help to co-relate the impact of variation in length with the bent's stress, strain and displacement.
9
Xu, Hang, Fujian Zhou, Hao Wu, Yuan Li, Lianqi Sheng e Erdong Yao. "Development and Evaluation of a Novel Delayed Crosslink, Low Friction, High-Density Brine-Based Fracturing Fluid for Ultra-Deep Fracturing Stimulation". In 56th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2022. http://dx.doi.org/10.56952/arma-2022-0983.
Testo completoAbstract (sommario):
ABSTRACT: Using heavyweight brines as a base for fracturing fluids is an effective method for solving the problem of exorbitant surface pressure during the deep well fracturing process. However, higher fluid densities can lead to higher friction pressures, and with the well depth increases, the travel time to the mudline prolongs, resulting in the demand for extended crosslink delay times. Therefore, fracturing fluids that provide flexibility in density, lower friction and extended crosslink times are required for effective stimulation in ultra-deep reservoirs. This paper presents details of laboratory studies to develop and evaluate a novel weighted fracturing fluid. The main additives of the novel system were sequentially synthesized, including modified guar gum, a new weighting agent and an organic boron-zirconium crosslinker. Afterwards, a series of lab experiments were carried out to test the comprehensive performances of the novel system, such as temperature and shear resistance, friction reduction, gel breaking performance and core damage rate. The optimal formula of fracturing fluid was 54.3 wt.% weighting agent + 0.4 wt.% modified guar gum + 1.0 wt.% pH regulator + 0.5 wt.% crosslinker. Results show that the novel weighted fracturing fluid is a good choice for ultra-deep reservoir hydraulic stimulation and hence improving the recovery. 1. INTRODUCTION Advancement of exploration and drilling technologies impel the oil and gas industry to extend the depth for hydrocarbons. Achieving efficient development of deep oil and gas is an important way for China’s recent oil and gas exploration and development (Xu et al., 2022; Lei et al., 2021; Wei et al., 2021). For major high-temperature and ultra-deep reservoirs in West China, hydraulic stimulation is facing some particular challenges. For instance, where the true vertical depth is more than 6000 m, there the rock fracturing pressure is often over 100 MPa and the temperature beyond 150 °C (Zhu et al., 2021; Ma et al., 2022). The traditional fracturing fluid system is difficult to play a role in the high-temperature deep well-fracturing process, and the weighted fracturing fluid system is a potential solution for deep well fracturing stimulation. At present, the formula of the weighted fracturing fluid system is not mature enough, and the upper limit of the density that can be weighted is restricted by economic and environmental protection (Wang et al., 2019; Yang et al., 2020; Qiu et al., 2009). Meanwhile, the weighted fluid system does not possess excellent friction reduction performance and cannot meet the requirements of deeper well fracturing stimulation. Therefore, it is essential to carry out the research on a novel weighted fracturing fluid system with high density, low friction and other excellent performances.
10
Schetz, Joseph A. "A Distributed and Distance Learning Course “Fluid Flows in Nature”". In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37220.
Testo completoAbstract (sommario):
This course was originally designed and conventionally taught to build upon and broaden a basic, traditional engineering knowledge of fluid flows into new and stimulating areas concerning a wide variety of natural occurrences and phenomena that involve fluid motions in important ways. Topics covered include: continuity and consequences in nature, drag of sessile systems and motile animals; gliding and soaring; flying and swimming; internal flows in organisms; low Reynolds number flows; fluid-fluid interfaces and stratified flows; unsteady flows in nature; atmospheric flows and wind engineering; and environmental fluid mechanics. The course is intended for upper-level students in engineering and science and presumes a background in the fundamentals of fluid flows at the level of a first engineering course in fluid mechanics. It proved popular with students majoring in mechanical, civil, aerospace and ocean engineering with occasional students from mathematics and sciences for a typical enrollment of 80–100 students. An unexpected, but welcome and powerful, benefit occurs in the form of reinforcing and deepening student understanding of traditional topics in engineering fluid mechanics by contrast with the often very different situations encountered in nature. An OnLine version of the course was introduced for the Spring Semester of 2006. Enrollment promptly and steadily increased to the point where 230 students registered in the Spring Semester of 2010. It is felt that a course of this type where conventional instructional materials do not exist is particularly suited to the OnLine format.
Rapporti di organizzazioni sul tema "Environmental fluid mechanics"
1
Lumley, John L. A Symposium: Fluid Mechanics and the Environment: Dynamical Approaches. Fort Belvoir, VA: Defense Technical Information Center, luglio 2000. http://dx.doi.org/10.21236/ada379218.
Testo completo
2
Kingston, A. W., O. H. Ardakani, G. Scheffer, M. Nightingale, C. Hubert e B. Meyer. The subsurface sulfur system following hydraulic stimulation of unconventional hydrocarbon reservoirs: assessing anthropogenic influences on microbial sulfate reduction in the deep subsurface, Alberta. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330712.
Testo completoAbstract (sommario):
Hydraulic fracturing is a reservoir stimulation technique that involves the injection of high-pressure fluids to enhance recovery from unconventional hydrocarbon reservoirs. Often this involves the injection of surface waters (along with additives such as biocides) into formational fluids significantly different isotopic and geochemical compositions facilitating geochemical fingerprinting of these fluid sources. In some instances, the produced fluids experience an increase in hydrogen sulfide (H2S) concentration over the course of production resulting in an increased risk to health and safety, the environment, and infrastructure due to the toxic and corrosive nature of H2S. However, questions remain as to the origin and processes leading to H2S formation following hydraulic fracturing. In this study, we analyzed a series of produced waters following hydraulic fracturing of a horizontal well completed in the Montney Formation, Western Canada to evaluate variations in geochemical and microbiological composition over time and characterize potential sulfur species involved in the production of H2S. Initially, sulfur isotope ratios (d34S, VCDT) of dissolved sulfate in produced water had a baseline value of 27per mil similar to the d34S value of 25per mil for solid anhydrite derived from core material. Subsequently, d34S values of sulfate in produced fluids sequentially increased to 35per mil coincident with the appearance of sulfides in produced waters with a d34SH2S value of 18per mil. Oxygen isotope values of dissolved sulfate exhibited a synchronous increase from 13.2per mil to 15.8per mil VSMOW suggesting sulfate reduction commenced in the subsurface following hydraulic fracturing. Formation temperatures are <100°C precluding thermochemical sulfate reduction as a potential mechanism for H2S production. We suggest that microbial reduction of anhydrite-derived sulfate within the formation is likely responsible for the increase in H2S within produced waters despite the use of biocides within the hydraulic fracturing fluids. Initial assessments of microbial communities indicate a shift in community diversity over time and interactions between in situ communities and those introduced during the hydraulic fracturing process. This study indicates that biocides may not be fully effective in inhibiting microbial sulfate reduction and highlights the role anthropogenic influences such as hydraulic fracturing can have on the generation of H2S in the subsurface.
3
Pailino, Lia, Lihua Lou, Alberto Sesena Rubfiaro, Jin He e Arvind Agarwal. Nanomechanical Properties of Engineered Cardiomyocytes Under Electrical Stimulation. Florida International University, ottobre 2021. http://dx.doi.org/10.25148/mmeurs.009775.
Testo completoAbstract (sommario):
Engineered cardiomyocytes made of human-induced pluripotent stem cells (iPSC) present phenotypical characteristics similar to human fetal cardiomyocytes. There are different factors that are essential for engineered cardiomyocytes to be functional, one of them being that their mechanical properties must mimic those of adult cardiomyocytes. Techniques, such as electrical stimulation, have been used to improve the extracellular matrix's alignment and organization and improve the intracellular environment. Therefore, electrical stimulation could potentially be used to enhance the mechanical properties of engineered cardiac tissue. The goal of this study is to establish the effects of electrical stimulation on the elastic modulus of engineered cardiac tissue. Nanoindentation tests were performed on engineered cardiomyocyte constructs under seven days of electrical stimulation and engineered cardiomyocyte constructs without electrical stimulation. The tests were conducted using BioSoft™ In-Situ Indenter through displacement control mode with a 50 µm conospherical diamond fluid cell probe. The Hertzian fit model was used to analyze the data and obtain the elastic modulus for each construct. This study demonstrated that electrically stimulated cardiomyocytes (6.98 ± 0.04 kPa) present higher elastic modulus than cardiomyocytes without electrical stimulation (4.96 ± 0.29 kPa) at day 7 of maturation. These results confirm that electrical stimulation improves the maturation of cardiomyocytes. Through this study, an efficient nanoindentation method is demonstrated for engineered cardiomyocyte tissues, capable of capturing the nanomechanical differences between electrically stimulated and non-electrically stimulated cardiomyocytes.
4
Weinberg, Zwi G., Richard E. Muck, Nathan Gollop, Gilad Ashbell, Paul J. Weimer e Limin Kung, Jr. effect of lactic acid bacteria silage inoculants on the ruminal ecosystem, fiber digestibility and animal performance. United States Department of Agriculture, settembre 2003. http://dx.doi.org/10.32747/2003.7587222.bard.
Testo completoAbstract (sommario):
The overall objective of the whole research was to elucidate the mechanisms by which LAB silage inoculants enhance ruminant performance. The results generated will permit the development of better silage inoculants that maximize both silage preservation and animal performance. For this one-year BARD feasibility study, the objectives were to: 1. determine whether lactic acid bacteria (LAB) used in inoculants for silage can survive in rumen fluid (RF) 2.select the inoculants that survived best, and 3. test whether LAB silage inoculants produce bacteriocins-like substances. The most promising strains will be used in the next steps of the research. Silage inoculants containing LAB are used in order to improve forage preservation efficiency. In addition, silage inoculants enhance animal performance in many cases. This includes improvements in feed intake, liveweight gain and milk production in 25-40% of studies reviewed. The cause for the improvement in animal performance is not clear but appears to be other than direct effect of LAB inoculants on silage fermentation. Results from various studies suggest a possible probiotic effect. Our hypothesis is that specific LAB strains interact with rumen microorganisms which results in enhanced rumen functionality and animal performance. The first step of the research is to determine whether LAB of silage inoculants survive in RF. Silage inoculants (12 in the U.S. and 10 in Israel) were added to clarified and strained RF. Inoculation rate was 10 ⁶ (clarified RF), 10⁷ (strained RF) (in the U.S.) and 10⁷, 10⁸ CFU ml⁻¹ in Israel (strained RF). The inoculated RF was incubated for 72 and 96 h at 39°C, with and without 5 g 1⁻¹ glucose. Changes in pH, LAB numbers and fermentation products were monitored throughout the incubation period. The results indicated that LAB silage inoculants can survive in RF. The inoculants with the highest counts after 72 h incubation in rumen fluid were Lactobacillus plantarum MTD1 and a L. plantarum/P. cerevisiae mixture (USA) and Enterococcus faecium strains and Lactobacillus buchneri (Israel). Incubation of rumen fluid with silage LAB inoculants resulted in higher pH values in most cases as compared with that of un-inoculated controls. The magnitude of the effect varied among inoculants and typically was enhanced with the inoculants that survived best. This might suggest the mode of action of LAB silage inoculants in the rumen as higher pH enhances fibrolytic microorganisms in the rumen. Volatile fatty acid (VFA) concentrations in the inoculated RF tended to be lower than in the control RF after incubation. However, L. plalltarull1 MTDI resulted in the highest concentrations of VFA in the RF relative to other inoculants. The implication of this result is not as yet clear. In previous research by others, feeding silages which were inoculated with this strain consistently enhanced animal performance. These finding were recently published in Weinberg et.al.. (2003), J. of Applied Microbiology 94:1066-1071 and in Weinberg et al.. (2003), Applied Biochemistry and Biotechnology (accepted). In addition, some strains in our studies have shown bacteriocins like activity. These included Pediococcus pentosaceus, Enterococcus faecium and Lactobacillus plantarum Mill 1. These results will enable us to continue the research with the LAB strains that survived best in the rumen fluid and have the highest potential to affect the rumen environment.
5
King, E. L., A. Normandeau, T. Carson, P. Fraser, C. Staniforth, A. Limoges, B. MacDonald, F. J. Murrillo-Perez e N. Van Nieuwenhove. Pockmarks, a paleo fluid efflux event, glacial meltwater channels, sponge colonies, and trawling impacts in Emerald Basin, Scotian Shelf: autonomous underwater vehicle surveys, William Kennedy 2022011 cruise report. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/331174.
Testo completoAbstract (sommario):
A short but productive cruise aboard RV William Kennedy tested various new field equipment near Halifax (port of departure and return) but also in areas that could also benefit science understanding. The GSC-A Gavia Autonomous Underwater Vehicle equipped with bathymetric, sidescan and sub-bottom profiler was successfully deployed for the first time on Scotian Shelf science targets. It surveyed three small areas: two across known benthic sponge, Vazella (Russian Hat) within a DFO-directed trawling closure area on the SE flank of Sambro Bank, bordering Emerald Basin, and one across known pockmarks, eroded cone-shaped depression in soft mud due to fluid efflux. The sponge study sites (~ 150 170 m water depth) were known to lie in an area of till (subglacial diamict) exposure at the seabed. The AUV data identified gravel and cobble-rich seabed, registering individual clasts at 35 cm gridded resolution. A subtle variation in seabed texture is recognized in sidescan images, from cobble-rich on ridge crests and flanks, to limited mud-rich sediment in intervening troughs. Correlation between seabed topography and texture with the (previously collected) Vazella distribution along two transects is not straightforward. However there may be a preference for the sponge in the depressions, some of which have a thin but possibly ephemeral sediment cover. Both sponge study sites depict a hereto unknown morphology, carved in glacial deposits, consisting of a series of discontinuous ridges interpreted to be generated by erosion in multiple, continuous, meandering and cross-cutting channels. The morphology is identical to glacial Nye, or mp;lt;"N-mp;lt;"channels, cut by sub-glacial meltwater. However their scale (10 to 100 times mp;lt;"typicalmp;gt;" N-channels) and the unique eroded medium, (till rather than bedrock), presents a rare or unknown size and medium and suggests a continuum in sub-glacial meltwater channels between much larger tunnel valleys, common to the eastward, and the bedrock forms. A comparison is made with coastal Nova Scotia forms in bedrock. The Emerald Basin AUV site, targeting pockmarks was in ~260 to 270 m water depth and imaged eight large and one small pockmark. The main aim was to investigate possible recent or continuous fluid flux activity in light of ocean acidification or greenhouse gas contribution; most accounts to date suggested inactivity. While a lack of common attributes marking activity is confirmed, creep or rotational flank failure is recognized, as is a depletion of buried diffuse methane immediately below the seabed features. Discovery of a second, buried, pockmark horizon, with smaller but more numerous erosive cones and no spatial correlation to the buried diffuse gas or the seabed pockmarks, indicates a paleo-event of fluid or gas efflux; general timing and possible mechanisms are suggested. The basinal survey also registered numerous otter board trawl marks cutting the surficial mud from past fishing activity. The AUV data present a unique dataset for follow-up quantification of the disturbance. Recent realization that this may play a significant role in ocean acidification on a global scale can benefit from such disturbance quantification. The new pole-mounted sub-bottom profiler collected high quality data, enabling correlation of recently recognized till ridges exposed at the seabed as they become buried across the flank and base of the basin. These, along with the Nye channels, will help reconstruct glacial behavior and flow patterns which to date are only vaguely documented. Several cores provide the potential for stratigraphic dating of key horizons and will augment Holocene environmental history investigations by a Dalhousie University student. In summary, several unique features have been identified, providing sufficient field data for further compilation, analysis and follow-up publications.