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1
Li, Yuehua y Trevor J. McDougall. "Double-Diffusive Interleaving: Properties of the Steady-State Solution". Journal of Physical Oceanography 45, n.º 3 (marzo de 2015): 813–35. http://dx.doi.org/10.1175/jpo-d-13-0236.1.
Resumen
AbstractDouble-diffusive interleaving is examined as it progresses from a linear instability toward finite amplitude. When the basic stratification is in the “finger” sense, the initial series of finger interfaces is unstable and one grows in strength at the expense of the others. At an intermediate stage of its development, the interleaving motions pass through a stage when every second interface in the vertical is stable to double diffusion. At a later time this interface turns into a “diffusive” double-diffusive interface. This study takes the fluxes of heat and salt across both the finger and diffusive interfaces to be given by the laboratory flux laws, and the authors ask whether a steady state is possible. It is found that the fluxes across the diffusive interfaces must be many times stronger relative to the corresponding fluxes across the finger interfaces than is indicated from existing flux expressions derived from laboratory experiments. The total effect of the interleaving motion on the vertical fluxes of heat and of salt are calculated for the steady-state solutions. It is found that both the fluxes of heat and salt are upgradient, corresponding to a negative vertical diffusion coefficient for all heat, salt, and density. For moderate to large Prandtl numbers, these negative effective diapycnal diffusivities of heat and salt are approximately equal so that the interleaving process acts to counteract some of the usual turbulent diapycnal diffusivity due to breaking internal waves.
2
Fleury, M. y R. G. Lueck. "Fluxes across a thermohaline interface". Deep Sea Research Part A. Oceanographic Research Papers 38, n.º 7 (julio de 1991): 745–69. http://dx.doi.org/10.1016/0198-0149(91)90017-a.
3
Yang, Li-Ming, Chang Shu, Wen-Ming Yang y Yan Wang. "Extension of lattice Boltzmann flux solver for simulation of compressible multi-component flows". Modern Physics Letters B 32, n.º 12n13 (10 de mayo de 2018): 1840001. http://dx.doi.org/10.1142/s0217984918400018.
Resumen
The lattice Boltzmann flux solver (LBFS), which was presented by Shu and his coworkers for solving compressible fluid flow problems, is extended to simulate compressible multi-component flows in this work. To solve the two-phase gas–liquid problems, the model equations with stiffened gas equation of state are adopted. In this model, two additional non-conservative equations are introduced to represent the material interfaces, apart from the classical Euler equations. We first convert the interface equations into the full conservative form by applying the mass equation. After that, we calculate the numerical fluxes of the classical Euler equations by the existing LBFS and the numerical fluxes of the interface equations by the passive scalar approach. Once all the numerical fluxes at the cell interface are obtained, the conservative variables at cell centers can be updated by marching the equations in time and the material interfaces can be identified via the distributions of the additional variables. The numerical accuracy and stability of present scheme are validated by its application to several compressible multi-component fluid flow problems.
4
Käser, Martin y Michael Dumbser. "A highly accurate discontinuous Galerkin method for complex interfaces between solids and moving fluids". GEOPHYSICS 73, n.º 3 (mayo de 2008): T23—T35. http://dx.doi.org/10.1190/1.2870081.
Resumen
We have extended a new highly accurate numerical scheme for unstructured 2D and 3D meshes based on the discontinuous Galerkin approach to simulate seismic wave propagation in heterogeneous media containing fluid-solid interfaces. Because of the formulation of the wave equations as a unified first-order hyperbolic system in velocity stress, the fluid can be in movement along the interface. The governing equations within the moving fluid are derived from well-known first principles in fluid mechanics. The discontinuous Galerkin approach allows for jumps of the material parameters and the solution across element interfaces, which are handled by Riemann solvers or numerical fluxes. The use of Riemann solvers at the element interfaces makesthe treatment of the fluid particularly simple bysetting the shearmodulus in the fluid region to zero. No additional compatibility relations, such as vanishing shear stress or continuity of normal stresses, are necessary to couple the solid and fluid along an interface. The Riemann solver automatically recognizes the jump of the material coefficients at the interface and provides the correct numerical fluxes for fluid-solid contacts. Therefore, wave propagation in the entire computational domain containing heterogeneous media, namely moving fluids and elastic solids, can be described by a uniform set of acoustic and elastic wave equations. The accuracy of the proposed scheme is confirmed by comparing numerical results against analytic solutions. The potential of the new method was demonstrated in a 3D model problem typical for marine seismic exploration with a fluid-solid interface determined by a complicated bathymetry.
5
GONZALEZ-JUEZ, ESTEBAN, ALAN R. KERSTEIN y DAVID O. LIGNELL. "Fluxes across double-diffusive interfaces: a one-dimensional-turbulence study". Journal of Fluid Mechanics 677 (12 de abril de 2011): 218–54. http://dx.doi.org/10.1017/jfm.2011.78.
Resumen
This work is a parametric study of the fluxes of heat and salt across unsheared and sheared double-diffusive interfaces using one-dimensional-turbulence (ODT) simulations. It is motivated by the need to understand how these fluxes scale with parameters related to the fluid molecular properties and background shear. Comparisons are made throughout with previous models and available measurements. In unsheared interfaces, ODT simulations show that the dimensionless heat fluxNuscales with the stability parameterRρ, Rayleigh numberRaand Prandtl numberPrasNu~ (Ra/Rρ)0.37±0.03whenPrvaries from 3 to 100 and asNu~ (Ra/Rρ)0.31Pr0.22±0.04whenPrvaries from 0.01 to 1. HereRa/Rρcan be seen as the ratio of destabilizing and stabilizing effects. The simulation results also indicate that the ratio of salt and heat fluxesRfis independent ofPr, scales with the Lewis numberLeasRf~Le0.41±0.04whenRρis large enough and deviates from this expression for low values ofRρ, when the interface becomes heavily eroded. In sheared interfaces, the simulations show three flow regimes. When the Richardson numberRi≪ 1, shear-induced mixing dominates, the heat flux scales with the horizontal velocity difference across the interface andRf=Rρ. NearRi~ 1 the heat and salt fluxes are seen to increase abruptly as the shear increases. The flow structure and scaling of the fluxes are similar to those of unsheared interfaces whenRi≫ 1.
6
Qi, Jin, Yue Wang y Jiequan Li. "Remapping-Free Adaptive GRP Method for Multi-Fluid Flows I: One Dimensional Euler Equations". Communications in Computational Physics 15, n.º 4 (abril de 2014): 1029–44. http://dx.doi.org/10.4208/cicp.140313.111013s.
Resumen
AbstractIn this paper, a remapping-free adaptive GRP method for one dimensional (1-D) compressible flows is developed. Based on the framework of finite volume method, the 1-D Euler equations are discretized on moving volumes and the resulting numerical fluxes are computed directly by the GRP method. Thus the remapping process in the earlier adaptive GRP algorithm [17,18] is omitted. By adopting a flexible moving mesh strategy, this method could be applied for multi-fluid problems. The interface of two fluids will be kept at the node of computational grids and the GRP solver is extended at the material interfaces of multi-fluid flows accordingly. Some typical numerical tests show competitive performances of the new method, especially for contact discontinuities of one fluid cases and the material interface tracking of multi-fluid cases.
7
Lorke, Andreas y Frank Peeters. "Toward a Unified Scaling Relation for Interfacial Fluxes". Journal of Physical Oceanography 36, n.º 5 (1 de mayo de 2006): 955–61. http://dx.doi.org/10.1175/jpo2903.1.
Resumen
Abstract Interfacial fluxes, that is, gas exchange at the water–atmosphere interface and benthic fluxes at the sediment–water interface, are often parameterized in terms of wind speed or turbulent friction velocity, with numerous empirical relationships obtained from individual experiments. The present study attempts to combine the general outcome of such experiments at both interfaces into a universal scaling relation for the thicknesses of the viscous and diffusive sublayers in terms of the Kolmogorov and Batchelor length scales, respectively. Transfer velocities can then be described in terms of the Schmidt number of the respective tracer and in terms of the turbulence dissipation rate. Applying law-of-the-wall scaling to convert dissipation rates into an appropriate friction velocity estimate results in a mechanistic description of the transfer velocity, which is comparable to common empirical parameterizations. It is hypothesized, however, that the dissipation rate and hence the directly estimated level of turbulence provide a more appropriate variable for the parameterization of interfacial fluxes than wind speed or turbulent friction velocity inferred from law-of-the-wall scaling.
8
Ilyin, Dan V. y Snezhana I. Abarzhi. "Interface dynamics with heat and mass fluxes". Physics Letters A 426 (febrero de 2022): 127827. http://dx.doi.org/10.1016/j.physleta.2021.127827.
9
Schmalzried, Hermann. "Chemical kinetics at solid-solid interfaces". Pure and Applied Chemistry 72, n.º 11 (1 de enero de 2000): 2137–47. http://dx.doi.org/10.1351/pac200072112137.
Resumen
The kinetics of solid-solid interfaces controls in part the course of heterogeneous reactions in the solid state, in particular in miniaturized systems. In this paper, the essential situations of interface kinetics in solids are defined, and the basic formal considerations are summarized. In addition to the role interfaces play as resistances for transport across them, they offer high diffusivity paths laterally and thus represent two-dimensional reaction media. Experimental examples will illustrate the kinetic phenomena at static and moving boundaries, including problems such as exchange fluxes, boundary-controlled solid-state reactions, interface morphology, nonlinear phenomena connected with interfaces, and reactions in and at boundaries, among others.
10
Carpenter, J. R. y M. L. Timmermans. "Does Rotation Influence Double-Diffusive Fluxes in Polar Oceans?" Journal of Physical Oceanography 44, n.º 1 (1 de enero de 2014): 289–96. http://dx.doi.org/10.1175/jpo-d-13-098.1.
Resumen
Abstract The diffusive (or semiconvection) regime of double-diffusive convection (DDC) is widespread in the polar oceans, generating “staircases” consisting of high-gradient interfaces of temperature and salinity separated by convectively mixed layers. Using two-dimensional direct numerical simulations, support is provided for a previous theory that rotation can influence DDC heat fluxes when the thickness of the thermal interface sufficiently exceeds that of the Ekman layer. This study finds, therefore, that the earth’s rotation places constraints on small-scale vertical heat fluxes through double-diffusive layers. This leads to departures from laboratory-based parameterizations that can significantly change estimates of Arctic Ocean heat fluxes in certain regions, although most of the upper Arctic Ocean thermocline is not expected to be dominated by rotation.
11
Chen, Bailing, Huilin Lai, Chuandong Lin y Demei Li. "Effects of Inclined Interface Angle on Compressible Rayleigh–Taylor Instability: A Numerical Study Based on the Discrete Boltzmann Method". Entropy 25, n.º 12 (5 de diciembre de 2023): 1623. http://dx.doi.org/10.3390/e25121623.
Resumen
Rayleigh–Taylor (RT) instability is a basic fluid interface instability that widely exists in nature and in the engineering field. To investigate the impact of the initial inclined interface on compressible RT instability, the two-component discrete Boltzmann method is employed. Both the thermodynamic non-equilibrium (TNE) and hydrodynamic non-equilibrium (HNE) effects are studied. It can be found that the global average density gradient in the horizontal direction, the non-organized energy fluxes, the global average non-equilibrium intensity and the proportion of the non-equilibrium region first increase and then reduce with time. However, the global average density gradient in the vertical direction and the non-organized moment fluxes first descend, then rise, and finally descend. Furthermore, the global average density gradient, the typical TNE intensity and the proportion of non-equilibrium region increase with increasing angle of the initial inclined interface. Physically, there are three competitive mechanisms: (1) As the perturbed interface elongates, the contact area between the two fluids expands, which results in an increasing gradient of macroscopic physical quantities and leads to a strengthening of the TNE effects. (2) Under the influence of viscosity, the perturbation pressure waves on both sides of the material interface decrease with time, which makes the gradient of the macroscopic physical quantity decrease, resulting in a weakening of the TNE strength. (3) Due to dissipation and/or mutual penetration of the two fluids, the gradient of macroscopic physical quantities gradually diminishes, resulting in a decrease in the intensity of the TNE.
12
Shen, Colin Y. "Heat‐salt finger fluxes across a density interface". Physics of Fluids A: Fluid Dynamics 5, n.º 11 (noviembre de 1993): 2633–43. http://dx.doi.org/10.1063/1.858727.
13
Frogner-Kockum, Paul, Peter Göransson, Henrik Åslund, Märta Ländell, Rodney Stevens, Anders Tengberg, Gunnel Göransson y Yvonne Ohlsson. "Metal contaminant fluxes across the sediment water interface". Marine Pollution Bulletin 111, n.º 1-2 (octubre de 2016): 321–29. http://dx.doi.org/10.1016/j.marpolbul.2016.06.092.
14
Atkinson, Joseph F. "Interfacial fluxes at a grid-stirred diffusive interface". International Journal of Heat and Mass Transfer 37, n.º 14 (septiembre de 1994): 2089–99. http://dx.doi.org/10.1016/0017-9310(94)90310-7.
15
Grant, A. L. M. "The cumulus-capped boundary layer. II: Interface fluxes". Quarterly Journal of the Royal Meteorological Society 132, n.º 618 (1 de julio de 2006): 1405–22. http://dx.doi.org/10.1256/qj.04.170.
16
Zhang, Meng, Robert A. Francis y Michael A. Chadwick. "Nutrient Dynamics at the Sediment-Water Interface: Influence of Wastewater Effluents". Environmental Processes 8, n.º 4 (1 de octubre de 2021): 1337–57. http://dx.doi.org/10.1007/s40710-021-00540-0.
Resumen
Abstract Uptake and regeneration fluxes and concentrations of nutrients, i.e., nitrate (NO3−), ammonium (NH4+), phosphate (PO43−) and dissolved organic carbon (DOC), were evaluated upstream and downstream of a wastewater treatment plant (WWTP) in the River Wandle, UK, from July to October 2019. Using chamber techniques, water-specific nutrient concentrations were measured at two exposures (3 and 10 min) to calculate fluxes. The WWTP effluent contributed to elevated concentrations and modified flux rates, resulting in significant differences at the study sites. Compared with summer, the concentrations of NO3− and DOC increased while NH4+ and PO43− decreased in autumn. Nutrient fluxes varied both temporally and spatially in uptake (i.e., storage in sediments) or regeneration (i.e., release into river water). Under the actions of physical and biological processes, the fluxes of NO3− and NH4+ showed opposite flux directions. Dissolved oxygen (DO) and bioabsorption mainly affected PO43− and DOC fluxes, respectively. Specifically, across all sites, NO3− was −0.01 to +0.02 mg/(m2 s), NH4+ was −29 to +2 μg/(m2 s), PO43− was −2.0 to +0.5 μg/(m2 s), and DOC was −0.01 to +0.05 mg/(m2 s). Further, we did find that these variations were related to nutrient concentrations in the overlying water. Our results provide further evidence to show that reductions in river nutrients are paramount for improving river ecological conditions. Additionally, we suggest that more research is needed to evaluate chamber-based experimental approaches to make them more comparable to in-situ flux methods. Highlights • Sewage effluent resulted in elevated nutrient concentrations and modified fluxes. • Flux was affected by initial nutrient concentrations, DO and microbial activity. • Inexpensive approaches to study nutrient dynamics are needed for river restoration.
17
Redeker, K. R., A. J. Baird y Y. A. Teh. "Quantifying wind and pressure effects on trace gas fluxes across the soil–atmosphere interface". Biogeosciences 12, n.º 24 (17 de diciembre de 2015): 7423–34. http://dx.doi.org/10.5194/bg-12-7423-2015.
Resumen
Abstract. Large uncertainties persist in estimates of soil–atmosphere exchange of important trace gases. One significant source of uncertainty is the combined effect of wind and pressure on these fluxes. Wind and pressure effects are mediated by surface topography: few surfaces are uniform and over scales of tenths of a metre to tens of metres, air pressure and wind speed at the ground surface may be very variable. In this paper we consider how such spatial variability in air pressure and wind speed affects fluxes of trace gases. We used a novel nested wind tunnel design comprising a toroidial wind tunnel, in which wind speed and pressure may be controlled, set within a larger, linear wind tunnel. The effects of both wind speed and pressure differentials on fluxes of CO2 and CH4 within three different ecosystems (forest, grassland, peat bog) were quantified. We find that trace gas fluxes are positively correlated with both wind speed and pressure differential near the surface boundary. We argue that wind speed is the better proxy for trace gas fluxes because of its stronger correlation and because wind speed is more easily measured and wind speed measurement methodology more easily standardized. Trace gas fluxes, whether into or out of the soil, increase with wind speed within the toroidal tunnel (+55 % flux per m s−1), while faster, localized surface winds that are external to the toroidal wind tunnel reduce trace gas fluxes (−13 % flux per m s−1). These results are consistent for both trace gases over all ecosystem soil types studied. Our findings support the need for a revised conceptualization of soil–atmosphere gas exchange. We propose a conceptual model of the soil profile that has a "mixed layer", with fluxes controlled by wind speed, wind duration, porosity, water table, and gas production and consumption.
18
Redeker, K. R., A. J. Baird y Y. A. Teh. "Quantifying wind and pressure effects on trace gas fluxes across the soil–atmosphere interface". Biogeosciences Discussions 12, n.º 6 (24 de marzo de 2015): 4801–32. http://dx.doi.org/10.5194/bgd-12-4801-2015.
Resumen
Abstract. Large uncertainties persist in estimates of soil–atmosphere exchange of important trace gases. One significant source of uncertainty is the combined effect of wind and pressure on these fluxes. Wind and pressure effects are mediated by surface topography: few surfaces are uniform and over scales of tenths of a meter to tens of meters, air pressure and wind speed at the ground surface may be very variable. In this paper we consider how such spatial variability in air pressure and wind speed affects fluxes of trace gases. We used a novel nested wind tunnel design, comprising a toroidial wind tunnel in which wind speed and pressure may be controlled, set within a larger, linear wind tunnel. The effects of both wind speed and pressure differentials on fluxes of CO2 and CH4 within three different ecosystems (forest, grassland, peat bog) were quantified. We find that trace gas fluxes are positively correlated with both wind speed and pressure differential near the surface boundary. We argue that wind speed is the better proxy for trace gas fluxes because of its stronger correlation and because wind speed measurement is more easily accomplished and wind speed measurement methodology can be more easily standardized. Trace gas fluxes, whether into or out of the soil, increase with wind speed within the toroidal tunnel (+54% flux per m s−1), while faster, localized surface winds that are external to the toroidal wind tunnel reduce trace gas fluxes (−11% flux per m s−1). These results are consistent for both trace gases over all ecosystem soil types studied. Our findings support the need for a revised conceptualization of soil–atmosphere gas exchange. We propose a conceptual model of the soil profile that has a "mixed layer", with fluxes controlled by wind speed, wind duration, porosity, water table, and gas production and consumption.
19
Formalev, V. F., S. A. Kolesnik y B. A. Garibyan. "Analytical Solution of the Problem of Conjugate Heat Transfer between a Gasdynamic Boundary Layer and Anisotropic Strip". Herald of the Bauman Moscow State Technical University. Series Natural Sciences, n.º 5 (92) (octubre de 2020): 44–59. http://dx.doi.org/10.18698/1812-3368-2020-5-44-59.
Resumen
The paper focuses on the problem of conjugate heat transfer between the thermal-gas-dynamic boundary layer and the anisotropic strip in conditions of aerodynamic heating of aircraft. Under the assumption of an incompressible flow which takes place in the shock layer behind the direct part of the shock wave, we found a new analytical solution for the components of the velocity vector, temperature distribution, and heat fluxes in the boundary layer. The obtained heat fluxes at the interface between the gas and the body are included as boundary conditions in the problem of anisotropic heat conduction in the body. The study introduces an analytical solution to the second initial-boundary value problem of heat conduction in an anisotropic strip with arbitrary boundary conditions at the interfaces, with heat fluxes which are obtained by solving the problem of a thermal boundary layer used at the interface. An analytical solution to the conjugate problem of heat transfer between a boundary layer and an anisotropic body can be effectively used to control, e.g. to reduce, heat fluxes from the gas to the body if the strip material chosen is such that the longitudinal component of the thermal conductivity tensor is many times larger than the transverse component of the thermal conductivity tensor. Such adjustment is possible due to an increase in body temperature in the longitudinal direction, and, consequently, a decrease in the heat flow from the gas to the body, as well as due to a favorable change in the physical characteristics of the gas. Results of numerical experiments are obtained and analyzed
20
Hannoun, Imad A., Harindra J. S. Fernando y E. John List. "Turbulence structure near a sharp density interface". Journal of Fluid Mechanics 189 (abril de 1988): 189–209. http://dx.doi.org/10.1017/s0022112088000965.
Resumen
The effects of a sharp density interface and a rigid flat plate on oscillating-grid induced shear-free turbulence were investigated experimentally. A two-component laser-Doppler velocimeter was used to measure turbulence intensities in and above the density interface (with matched refractive indices) and near the rigid flat plate. Energy spectra, velocity correlations, and kinetic energy fluxes were also measured. Amplification of the horizontal turbulent velocity, coupled with a sharp reduction in the vertical turbulent velocity, was observed near both the density interface and the flat plate. These findings are in agreement with some previous results pertaining to shear-free turbulence near rigid walls (Hunt & Graham 1978) and near density interfaces (Long 1978). The results imply that, near the density interface, the turbulent kinetic energy in the vertical velocity component is only a small fraction of the total turbulent kinetic energy and indicate that the effects of the anisotropy created by the density interface or the flat plate are confined to the large turbulence scales.
21
Fitzsimmons, Jessica y Janelle Steffen. "The “Net” Impact of Hydrothermal Venting on Oceanic Elemental Inventories: Contributions to Plume Geochemistry from the International GEOTRACES Program". Oceanography 37, n.º 2 (2024): 102–15. http://dx.doi.org/10.5670/oceanog.2024.421.
Resumen
Hydrothermal vents serve as a primary interface between the cold deep ocean and the warm oceanic crust. While early research showed that seawater-rock interactions add to or remove elements from seawater during the generation of hydrothermal fluids, consideration of these fluid fluxes alone does not relay the total impact that hydrothermal systems have on seawater geochemistry. In addition, hydrothermal plumes, areas where hydrothermal fluids mix with ocean waters, are host to a range of particle precipitation and scavenging reactions that further modify gross hydrothermal fluid fluxes to define the total “net” hydrothermal impact on oceanic inventories. Here, we review the major discoveries made by the international GEOTRACES program regarding the geochemical transformations occurring within hydrothermal plumes. We classify each element into one of five categories based on its behavior in hydrothermal plumes, a spectrum spanning the geochemical mass balance between net hydrothermal source fluxes and net hydrothermal plume scavenging sinks. Overall, we celebrate the role that GEOTRACES has played in defining the extent and dynamics of hydrothermal plume geochemistry, which is a crucial lever for determining global hydrothermal impacts.
22
JACQMIN, DAVID. "Contact-line dynamics of a diffuse fluid interface". Journal of Fluid Mechanics 402 (10 de enero de 2000): 57–88. http://dx.doi.org/10.1017/s0022112099006874.
Resumen
An investigation is made into the moving contact line dynamics of a Cahn–Hilliard–van der Waals (CHW) diffuse mean-field interface. The interface separates two incompressible viscous fluids and can evolve either through convection or through diffusion driven by chemical potential gradients. The purpose of this paper is to show how the CHW moving contact line compares to the classical sharp interface contact line. It therefore discusses the asymptotics of the CHW contact line velocity and chemical potential fields as the interface thickness ε and the mobility κ both go to zero. The CHW and classical velocity fields have the same outer behaviour but can have very different inner behaviours and physics. In the CHW model, wall–liquid bonds are broken by chemical potential gradients instead of by shear and change of material at the wall is accomplished by diffusion rather than convection. The result is, mathematically at least, that the CHW moving contact line can exist even with no-slip conditions for the velocity. The relevance and realism or lack thereof of this is considered through the course of the paper.The two contacting fluids are assumed to be Newtonian and, to a first approximation, to obey the no-slip condition. The analysis is linear. For simplicity most of the analysis and results are for a 90° contact angle and for the fluids having equal dynamic viscosity μ and mobility κ. There are two regions of flow. To leading order the outer-region velocity field is the same as for sharp interfaces (flow field independent of r) while the chemical potential behaves like r−ξ, ξ = π/2/max{θeq, π − θeq}, θeq being the equilibrium contact angle. An exception to this occurs for θeq = 90°, when the chemical potential behaves like ln r/r. The diffusive and viscous contact line singularities implied by these outer solutions are resolved in the inner region through chemical diffusion. The length scale of the inner region is about 10√μκ – typically about 0.5–5 nm. Diffusive fluxes in this region are O(1). These counterbalance the effects of the velocity, which, because of the assumed no-slip boundary condition, fluxes material through the interface in a narrow boundary layer next to the wall.The asymptotic analysis is supplemented by both linearized and nonlinear finite difference calculations. These are made at two scales, experimental and nanoscale. The first set is done to show CHW interface behaviour and to test the qualitative applicability of the CHW model and its asymptotic theory to practical computations of experimental scale, nonlinear, low capillary number flows. The nanoscale calculations are carried out with realistic interface thicknesses and diffusivities and with various assumed levels of shear-induced slip. These are discussed in an attempt to evaluate the physical relevance of the CHW diffusive model. The various asymptotic and numerical results together indicate a potential usefullness for the CHW model for calculating and modelling wetting and dewetting flows.
23
Gehlen, M., L. Bopp, N. Emprin, O. Aumont, C. Heinze y O. Ragueneau. "Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model". Biogeosciences Discussions 3, n.º 3 (28 de junio de 2006): 803–36. http://dx.doi.org/10.5194/bgd-3-803-2006.
Resumen
Abstract. This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1) the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2) an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3) a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. The integrated representation of material fluxes from the productive surface ocean down to the sediment-water interface allows taking advantage of surface ocean observations, sediment trap data and exchange fluxes at the sediment-water interface. The capability of the model to reproduce yearly averaged particulate organic carbon fluxes and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Model results obtained with the standard version and with the one including a particle size spectrum and prognostic sinking speed are not significantly different. Both model versions overestimate particulate organic carbon between 1000 and 2000 m, while deep fluxes are of the correct order of magnitude. Predicted benthic oxygen fluxes correspond with respect to their large scale distribution and magnitude to data based estimates. Modeled particulate organic C fluxes across the mesopelagos are most sensitive to the intensity of zooplankton flux feeding. An increase of the intensity of flux feeding in the standard version results in lower mid- and deep-water particulate organic carbon fluxes, shifting model results to an underestimation of particulate organic carbon fluxes in the deep. The corresponding benthic oxygen fluxes are too low. The model version including the mineral ballast parameterization yields an improved fit between modeled and observed particulate organic carbon fluxes below 2000 m and down to the sediment-water interface. Our results suggest that aggregate formation alone might not be sufficient to drive an intense biological pump. The later is most likely driven by the combined effect of aggregate formation and mineral ballasting.
24
Coutinho de Lima, Adriano. "Lateral Momentum Fluxes at the Confluence of the Negro and Solimões Rivers". Geosciences 9, n.º 1 (23 de diciembre de 2018): 7. http://dx.doi.org/10.3390/geosciences9010007.
Resumen
Hydrodynamic zones of river confluences are remarkable not only for the turbulent mixing induced by the shear layer at the center of the mixing interface but also for the lateral momentum fluxes associated with channel topography. Detailed characterizations of lateral momentum transfers in river confluences, however, are few. In this study, contributions to the lateral momentum fluxes in the confluence of the Negro and Solimões rivers in Brazil were calculated based on a comprehensive set of field data. Results show that the lateral fluxes by the mean flow exceed the turbulent fluxes by two orders of magnitude. Furthermore, the Reynolds stress along the far field of the Solimões side of the Amazon channel scales with or surpasses the Reynolds stress at the interface with the Negro side. The importance of the shear layer in the lateral mixing is thus overshadowed by the competing hydrodynamic processes. This configuration partially explains the long distance required to complete the mixing of the waters of the two tributary rivers.
25
Cui, Wenhui y Ting Fong May Chui. "Subsurface Lateral Heat Flux within the Heterogeneous Surface of a Subtropical Wetland and Its Potential Contribution to Energy Imbalance". Journal of Hydrometeorology 18, n.º 12 (30 de noviembre de 2017): 3125–44. http://dx.doi.org/10.1175/jhm-d-17-0006.1.
Resumen
Abstract In the eddy covariance technique, lateral heat fluxes in the atmosphere, surfaces, and subsurfaces are often ignored under the assumption of a homogeneous surface. Among lateral heat fluxes, the surface and subsurface fluxes, which might affect the surface energy balance closure over a heterogeneous surface, are less studied. Many wetlands are heterogeneous, with a mix of vegetated areas and shallow open water. This study examined the subsurface lateral heat fluxes between a reed bed and the adjacent water of a subtropical wetland in Hong Kong, China. An array of temperature and water-level sensors was installed in the soil of the reed bed and in the adjacent water. An eddy covariance system was also set up on the reed bed. The subsurface lateral heat fluxes were largest close to the interface of the reed bed and water and decreased as the distance from the interface increased, as expected. However, the subsurface lateral heat fluxes could not account for the energy imbalance because their magnitudes were relatively small and fluctuated in phase with the energy budget residuals during the winter months. The uncertainties of the turbulent fluxes and the lateral heat fluxes were estimated to be 10%–20% and 10%–30%, respectively. This study explored another potential reason behind the energy imbalance of the eddy covariance technique. The results enhance the understanding of water and energy exchanges between a terrestrial biotope and the surrounding water, which might further generate insights into the biochemical processes in wetlands.
26
Mueller, James A. y Fabrice Veron. "Bulk Formulation of the Heat and Water Vapor Fluxes at the Air–Sea Interface, Including Nonmolecular Contributions". Journal of the Atmospheric Sciences 67, n.º 1 (1 de enero de 2010): 234–47. http://dx.doi.org/10.1175/2009jas3061.1.
Resumen
Abstract Accurate prediction of the air–sea sensible and latent heat fluxes is vital for nearly all applications of atmosphere and ocean models. Existing theories of heat transfer over rough surfaces provide a starting point, but they seem incomplete given that recent measurements suggest a departure from these theoretically predicted fluxes at higher wind speeds. Although explicit models of the air–sea heat fluxes are desperately needed, the formulation presented in this paper is an attempt to model the air–sea fluxes without dependence on explicit heat flux components. Using smooth flow limit approximations, theoretical profiles, and a physically based surface stress model, the predicted heat fluxes show reasonable agreement with available data. With increasing wind forcing, modestly increasing heat and moisture exchange coefficients (Stanton and Dalton numbers) are found. Even though wave age strongly influences the surface drag, stratification and temperature effects seem to dominate the wave-age influence on the air–sea heat and moisture fluxes.
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Andreas, Edgar L., P. Ola G. Persson y Jeffrey E. Hare. "A Bulk Turbulent Air–Sea Flux Algorithm for High-Wind, Spray Conditions". Journal of Physical Oceanography 38, n.º 7 (1 de julio de 2008): 1581–96. http://dx.doi.org/10.1175/2007jpo3813.1.
Resumen
Abstract Sensible and latent heat can cross the air–sea interface by two routes: as interfacial fluxes controlled by molecular processes right at the interface, and as spray fluxes from the surface of sea spray droplets. Once the 10-m wind speed over the ocean reaches approximately 11–13 m s−1, the spray sensible and latent heat fluxes become significant fractions (i.e., 10% or greater) of the corresponding interfacial fluxes. The analysis here establishes that result by combining the Tropical Ocean-Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (COARE) version 2.6 bulk interfacial flux algorithm with a microphysical spray model to partition measured heat fluxes from two good high-wind datasets into spray and interfacial flux contributions. The measurements come from the Humidity Exchange over the Sea (HEXOS) experiment and the Fronts and Atlantic Storm-Tracks Experiment (FASTEX); wind speeds in these two datasets span 5 to 20 m s−1. After the measured heat fluxes are separated into spray and interfacial contributions, the spray fluxes are used to develop a fast spray flux algorithm to combine with the COARE version 2.6 interfacial flux algorithm in a unified turbulent surface flux algorithm for use in large-scale and ocean storm models. A sensitivity analysis of the spray and interfacial components of this unified flux algorithm demonstrates how the two component fluxes scale differently with the mean meteorological variables and why they must therefore be parameterized separately in models intended to treat air–sea fluxes in high winds.
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Chatterjee, P., G. Guerrero y A. Brandenburg. "Magnetic helicity fluxes in interface and flux transport dynamos". Astronomy & Astrophysics 525 (26 de noviembre de 2010): A5. http://dx.doi.org/10.1051/0004-6361/201015073.
29
Anisimova, E. P., K. V. Pokazeev y A. A. Speranskaya. "Redistribution of momentum fluxes on the water-air interface". Physical Oceanography 10, n.º 4 (julio de 2000): 323–30. http://dx.doi.org/10.1007/bf02519304.
30
Briantsev, K. A. y V. U. Sidyganov. "He-II - Vapour interface stability at high heat fluxes". Cryogenics 32 (enero de 1992): 253–55. http://dx.doi.org/10.1016/0011-2275(92)90156-5.
31
Atkinson, J. F., E. Eric Adams y D. R. F. Harleman. "Double-Diffusive Fluxes in a Salt Gradient Solar Pond". Journal of Solar Energy Engineering 110, n.º 1 (1 de febrero de 1988): 17–22. http://dx.doi.org/10.1115/1.3268231.
Resumen
The possible influence of double-diffusive stratification on the vertical transport of salt and heat in a mixed-layer simulation model for a salt gradient solar pond is examined. The study is concerned primarily with the interfacial fluxes across the boundary between the gradient zone and upper convecting zone of solar ponds, though the arguments presented should be applicable to other “diffusive” interfaces as well. In the absence of mechanical stirring in the upper convecting zone (e.g., by wind), double diffusive instabilities could govern the vertical flux of heat and salt by adjusting interfacial gradients of temperature and salinity which control transport by molecular diffusion. Because these gradients are generally too sharp to be resolved by numerical models, the fluxes can either be modeled directly or be parameterized by grid-dependent “effective diffusivities.” It is shown that when mechanical stirring is present in the mixed layer, double-diffusive instabilities will not be allowed to grow in the interfacial boundary layer region. Thus, double-diffusive fluxes become important only in the absence of stirring and, in effect, provide a lower bound to the fluxes that would be expected across the interface.
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Gusak, Andriy, Guido Schmitz y Nadiya Storozhuk. "Flux Driven Nucleation at Interfaces during Reactive Diffusion – New Solution of an Old Problem". Defect and Diffusion Forum 323-325 (abril de 2012): 55–60. http://dx.doi.org/10.4028/www.scientific.net/ddf.323-325.55.
Resumen
The problem of phase competition during reactive diffusion is revisited. Nucleation of an intermediate phase at an interface under external fluxes in the neighboring phases is considered in the frame of kinetic Fokker-Planck approach. Effective nucleation barrier depending on the divergence of external fluxes is introduced. New suppression/growth criteria are obtained.
33
Richard, Marion, Philippe Archambault, Gérard Thouzeau y Gaston Desrosiers. "Influence of suspended mussel lines on the biogeochemical fluxes in adjacent water in the Îles-de-la-Madeleine (Quebec, Canada)". Canadian Journal of Fisheries and Aquatic Sciences 63, n.º 6 (1 de junio de 2006): 1198–213. http://dx.doi.org/10.1139/f06-030.
Resumen
Oxygen consumption and nutrient fluxes were measured in 80 L enclosures containing water, 1- or 2-year-old mussels, or 1- or 2-year-old line sections (mussels plus associated fauna organic matter complex: AFOM) in August and September 2003 in the Îles-de-la-Madeleine. Mussel lines acted as nutrient sources and oxygen sinks in adjacent water. The magnitude of fluxes at the mussel line interface depended on the nutrient (NH4 >> Si(OH)4, PO4 > NO3 > NO2). Mussel metabolism contributed greatly to O2 consumption and NH4 and PO4 releases. Mussel influence was greater in stressful periods. The AFOM complex mainly contributed to NO3, NO2, and Si(OH)4 fluxes. These fluxes could originate from organic matter decomposition rather than from associated faunal metabolism. The influence of AFOM depended on its composition and thus on line immersion time. Mussel lines by ammonia releases could be a factor of reduction of N limitation in the water column. Mussel line should be integrated as a new interface of biogeochemical exchanges in environmental carrying capacity studies.
34
Guo, Yuhao, Yan Wang, Qiqi Hao y Tongguang Wang. "An Interface-Corrected Diffuse Interface Model for Incompressible Multiphase Flows with Large Density Ratios". Applied Sciences 12, n.º 18 (18 de septiembre de 2022): 9337. http://dx.doi.org/10.3390/app12189337.
Resumen
An interface-corrected diffuse interface method is presented in this work for the simulation of incompressible multiphase flows with large density ratios. In this method, an interface correction term together with a mass correction term is introduced into the diffuse-interface Cahn–Hilliard model to maintain both mass conservation and interface shapes between binary fluids simultaneously. The interface correction term is obtained by connecting the signed distance functions in the Hamilton–Jacobian equation with the order parameter of the Cahn–Hilliard model. In addition, an improved multiphase lattice Boltzmann flux solver is introduced, in which the fluxes are obtained by considering the contributions of the particle distribution functions before and after the streaming process through a local switch function. The proposed method is validated by simulating multiphase flows, such as the Laplace law, the evolution of a square bubble, the merging of two bubbles, Rayleigh–Taylor instability, and a droplet impacting on a film with a density ratio of 1000. Numerical results show that the presented method can not only reduce the interface diffusion but also has good control over the interface thickness and mass conservation. The improved numerical method has great potential for use in practical applications involving multiphase flows.
35
Lourino-Cabana, Beatriz, Ludovic Lesven, Gabriel Billon, Lionel Denis, Baghdad Ouddane y Abdel Boughriet. "Benthic exchange of sedimentary metals (Cd, Cu, Fe, Mn, Ni and Zn) in the Deûle River (Northern France)". Environmental Chemistry 9, n.º 5 (2012): 485. http://dx.doi.org/10.1071/en12046.
Resumen
Environmental context Exchange processes at the water–sediment interface can release metals to riverine waters, having negative effects on organisms in the water column. We investigate the geochemical processes and metal exchange between the surface sediment and the overlying water under metal contamination conditions. Results suggest that the sediment can be a significant source of metal pollution in aquatic systems, particularly during anoxic events. Abstract Experiments were performed on the Deûle River (Northern France), which is strongly polluted by smelting plants, in the aim to investigate the influence of diagenetic processes and benthic macro-faunal activity on trace metal (Cd, Cu, Ni and Zn) and major metal (Fe, Mn) exchanges occurring at the water–sediment interface. Diffusive metal fluxes were determined from pore water metal concentration gradients measured in sediment cores. Benthic metal fluxes were evaluated using incubation chambers under dark conditions, and by further examining key variables (O2, CO2, redox potential and pH) affecting metal release and sequestration processes. As a whole, it was demonstrated that benthic fluxes were strongly dependent upon medium oxygenation and generation of colloidal iron oxides and hydroxides at the overlying water–sediment interface, raising the possibility of trace-metal adsorption and (co)precipitation.
36
Mazhukin, V. I. y M. M. Chuiko. "SOLUTION OF TWO‐DIMENSIONAL MULTI‐INTERFACE STEFAN PROBLEM BY THE METHOD OF DYNAMIC ADAPTATION". Mathematical Modelling and Analysis 6, n.º 1 (30 de junio de 2001): 129–37. http://dx.doi.org/10.3846/13926292.2001.9637152.
Resumen
In the present work a method of numerical solution of multi‐interface two-dimensional Stefan problem with explicit tracking of the interfaces in the domains of arbitrary form is considered. The method is based on the idea of dynamic adaptation of the calculated grid by means of transition to an arbitrary non-stationary coordinate system. The coordinate system transformation is controlled by the solution. The method is described by using the example of the problem that is typical for treatment of materials with concentrated energy fluxes.
37
Audusse, Emmanuel y Benoît Perthame. "Uniqueness for scalar conservation laws with discontinuous flux via adapted entropies". Proceedings of the Royal Society of Edinburgh: Section A Mathematics 135, n.º 2 (abril de 2005): 253–65. http://dx.doi.org/10.1017/s0308210500003863.
Resumen
We prove uniqueness of solutions to scalar conservation laws with space discontinuous fluxes. To do so, we introduce a partial adaptation of Kružkov's entropies which naturally takes into account the space dependency of the flux. The advantage of this approach is that the proof turns out to be a simple variant of the original method of Kružkov. In particular, we do not need traces, interface conditions, bounded variation assumptions (neither on the solution nor on the flux), or convex fluxes. However, we use a special ‘local uniform invertibility’ structure of the flux, which applies to cases where different interface conditions are known to yield different solutions
38
Floreani, Federico, Alessandro Acquavita, Nicolò Barago, Katja Klun, Jadran Faganeli y Stefano Covelli. "Gaseous Mercury Exchange from Water–Air Interface in Differently Impacted Freshwater Environments". International Journal of Environmental Research and Public Health 19, n.º 13 (2 de julio de 2022): 8149. http://dx.doi.org/10.3390/ijerph19138149.
Resumen
Gaseous exchanges of mercury (Hg) at the water–air interface in contaminated sites strongly influence its fate in the environment. In this study, diurnal gaseous Hg exchanges were seasonally evaluated by means of a floating flux chamber in two freshwater environments impacted by anthropogenic sources of Hg, specifically historical mining activity (Solkan Reservoir, Slovenia) and the chlor-alkali industry (Torviscosa dockyard, Italy), and in a pristine site, Cavazzo Lake (Italy). The highest fluxes (21.88 ± 11.55 ng m−2 h−1) were observed at Solkan, coupled with high dissolved gaseous mercury (DGM) and dissolved Hg (THgD) concentrations. Conversely, low vertical mixing and saltwater intrusion at Torviscosa limited Hg mobility through the water column, with higher Hg concentrations in the deep layer near the contaminated sediments. Consequently, both DGM and THgD in surface water were generally lower at Torviscosa than at Solkan, resulting in lower fluxes (19.01 ± 12.65 ng m−2 h−1). However, at this site, evasion may also be limited by high atmospheric Hg levels related to dispersion of emissions from the nearby chlor-alkali plant. Surprisingly, comparable fluxes (15.56 ± 12.78 ng m−2 h−1) and Hg levels in water were observed at Cavazzo, suggesting a previously unidentified Hg input (atmospheric depositions or local geology). Overall, at all sites the fluxes were higher in the summer and correlated to incident UV radiation and water temperature due to enhanced photo production and diffusivity of DGM, the concentrations of which roughly followed the same seasonal trend.
39
Bumke, Karl, Michael Schlundt, John Kalisch, Andreas Macke y Henry Kleta. "Measured and Parameterized Energy Fluxes Estimated for Atlantic Transects of R/V Polarstern". Journal of Physical Oceanography 44, n.º 2 (1 de febrero de 2014): 482–91. http://dx.doi.org/10.1175/jpo-d-13-0152.1.
Resumen
Abstract Sensible and latent heat fluxes were estimated from turbulence measurements gathered during several Atlantic Ocean transects of the research vessel (R/V) Polarstern. The inertial dissipation method was used to analyze the data. Resulting bulk transfer coefficients were then applied to the data from the ship’s meteorological system to get continuous time series of the heat fluxes. Combined with the measured downward solar and longwave radiation fluxes it allows for an estimate of the total energy budget at the air–sea interface. Comparing these parameterized energy fluxes to those based on the Coupled Ocean–Atmosphere Response Experiment, version 3 (COARE3.0), bulk flux algorithm shows very strong agreement.
40
Long, M. H., D. Koopmans, P. Berg, S. Rysgaard, R. N. Glud y D. H. Søgaard. "Oxygen exchange and ice melt measured at the ice-water interface by eddy correlation". Biogeosciences Discussions 8, n.º 6 (23 de noviembre de 2011): 11255–84. http://dx.doi.org/10.5194/bgd-8-11255-2011.
Resumen
Abstract. This study uses the eddy correlation technique to examine fluxes across the ice-water interface. Temperature eddy correlation systems were used to determine rates of ice melting and freezing, and O2 eddy correlation systems were used to examine O2 exchange rates as driven by biological and physical processes. The research was conducted below 0.7 m thick sea ice in mid March 2010 in a southwest Greenland fjord and revealed low average rates of ice melt amounting to a maximum of 0.80 ± 0.09 mm d−1 (SE, n=31). The corresponding calculated O2 flux associated with release of O2 depleted melt water was less than 13 % of the average daily O2 respiration rate. Ice melt and insufficient vertical turbulent mixing due to low current velocities caused periodic stratification immediately below the ice. This prevented the determination of fluxes during certain time periods, amounting to 66 % of total deployment time. The identification of these conditions was evaluated by examining the velocity and the linearity and stability of the cumulative flux. The examination of unstratified conditions through velocity and O2 spectra and their cospectra revealed characteristic fingerprints of well-developed turbulence. From the observed O2 fluxes, a photosynthesis/irradiance curve was established by least-squares fitting. This relation showed that light limitation of net photosynthesis began at 4.2 μmol photons m−2 s−1, and that the algal communities were well-adapted to low-light conditions as they were light saturated for 75 % of the day during this early spring period. However, the sea ice associated microbial and algal community was net heterotrophic with a daily gross primary production of 0.69 ± 0.02 mmol O2 m−2 d−1 (SE, n=4) and a respiration rate of −2.13 mmol O2 m−2 d−1 (no SE, see text for details) leading to a net primary production of −1.45 ± 0.02 mmol O2 m−2 d−1 (SE, n=4). Modeling the observed fluxes allowed for the calculation of fluxes during time periods when no O2 fluxes were extracted. This application of the eddy correlation technique produced high temporal resolution O2 fluxes and ice melt rates that were measured without disturbing the environmental conditions while integrating over a large area of approximately 50 m2 which encompassed the highly variable activity and spatial distributions of sea ice algal communities.
41
Machado, Daniela Vasconcelos, Gerson Cardoso da Silva Júnior, Eduardo Duarte Marques y Emmanoel Vieira Silva-Filho. "CO2 fluxes at the water-atmosphere interface in fluvial environments: an overview of studies in Brazilian rivers". Ambiente e Agua - An Interdisciplinary Journal of Applied Science 18 (8 de septiembre de 2023): 1–15. http://dx.doi.org/10.4136/ambi-agua.2921.
Resumen
Recent advances in Brazilian scientific production on CO2 fluxes at the water-atmosphere interface in rivers were reviewed, including estimates of CO2 partial pressure and fluxes. A total of 17 studies were reviewed. We compiled information regarding the location studied, the methodology used by each author, and the values of CO2 partial pressure (pCO2), CO2 fluxes (FCO2), and gas exchange coefficient (k) found in each region. The results were spatialized and synthesized. The important role of fluxes in CO2 degassing and their influence on climate change, as well as the global lack of data on these environments, were the main motivations for this study. The information was scarce, and most studies are focused on the Amazon Basin. However, high-resolution mapping of CO2 fluxes, at the scale of micro basins and streams, proved to be scarce. We emphasize, therefore, the importance of further studies in the country including other hydrographic regions, and in high resolution. These studies would add to our knowledge of how natural and anthropic processes influence CO2 flux, in addition to providing better estimates in tropical river systems.
Keywords: climate change, CO2 emission, CO2 partial pressure.
42
van Raaphorst, W. y A. G. Brinkman. "The Calculation of Transport Coefficients of Phosphate and Calcium Fluxes Across the Sediment-Water Interface, from Experiments with Undisturbed Sediment Cores". Water Science and Technology 17, n.º 6-7 (1 de junio de 1985): 941–51. http://dx.doi.org/10.2166/wst.1985.0192.
Resumen
Fluxes of phosphate and calcium across the sediment-water interface of six undisturbed cores are investigated. Attention is paid to the accuracy of porewater extraction and the influence of this sampling upon the experiments. From this, it is concluded that sampling time should at least be one day. Continuous and batch experiments resulted in a rapid release of phosphorus and calcium from the sediment. The influence of induced seepage could not be shown. On a theoretical base, it is concluded that the benthic fluxes are fed by desorption at or just below the interface, rather than by diffusion from deeper layers. Hence, data of interstitial water could not directly be used for calculating the driving forces of these fluxes. Instead, endconcentrations in the overlaying water of the batch experiments are used, which resulted in values of transportcoefficients of 3–10.10−7 m.s−1, being in good agreement with theoretical as well as field data.
43
STAMP, ANDREW P., GRAHAM O. HUGHES, ROGER I. NOKES y ROSS W. GRIFFITHS. "The coupling of waves and convection". Journal of Fluid Mechanics 372 (10 de octubre de 1998): 231–71. http://dx.doi.org/10.1017/s0022112098002304.
Resumen
Experiments with layers of salt and sugar solution separated by a diffusive interface are described. Interfacial waves were spontaneously generated by the convection once the system evolved to a critical value of the density-anomaly ratio Rρ≡βΔS/αΔT. The waves locally modulated the interfacial fluxes by modifying the interface thickness and thereby organized otherwise random convective motions into large-scale circulations. In turn, the waves themselves persisted for unusually long times owing to energy input from the organized convection. The dependence of the wave speed on the layer properties and channel dimensions was successfully predicted by assuming that coupling requires a matching of the wave and convection speeds, and that the system selects waves of an amplitude for which this resonance can occur. This ‘wave–convection coupling’ also appeared to increase the interfacial fluxes at low Rρ. The interaction of waves and convection may be important for oceanic thermohaline staircases and other systems where convection is driven by interfacial fluxes.
44
Barbanti, A., MC Bergamini, F. Frascari, S. Miserocchi, M. Ratta y G. Rosso. "Diagenetic processes and nutrient fluxes at the sediment-water interface, northern Adriatic Sea, Italy". Marine and Freshwater Research 46, n.º 1 (1995): 55. http://dx.doi.org/10.1071/mf9950055.
Resumen
Early diagenetic processes that control pore-water chemistry and nutrient fluxes at the sediment-water interface were studied in late summer 1989 and spring 1990 at four sites influenced by fine sediments of the Po River. Parameters on the solid fraction (grain size and C, N and P) and pore- water profiles of SO42-, NO3-, NH3, alkalinity, PO43-, Fe, Mn, Ca and Mg were determined. Data interpretation was supported by application of kinetic and stoichiometric modelling. Nutrient fluxes were calculated by Fick's first law. In the prodelta station the pore-water profiles showed large depletion in SO42- ions, jointly with the increase with depth of alkalinity, NH3 and PO43- concentrations, thus indicating anaerobic decomposition of organic matter, mainly due to bacterial sulfate reduction. At the other three sites the results were completely different. Nutrient concentrations in pore water were one order of magnitude lower. The peaks of alkalinity, NH3 and PO43- values near the interface and the constant presence of SO42- ions indicate aerobic decomposition of organic matter in the uppermost sediment. Nutrient fluxes showed much higher values in the prodelta station, whereas fluxes in the remaining stations decreased southward. In addition, seasonal variations produced higher summertime fluxes. The clear-cut difference in diagenetic processes as a function of the distance from the main Po River mouth can be explained by the rapid burial of sediments rich in organic matter and inorganic compounds in the prodelta station. At the other stations, the lower sedimentation rate and more efficient bioturbation and resuspension processes cause a prolonged exposure of sediments to aerobic metabolization reactions before burial.
45
Zhang, Xiangxiong y Sirui Tan. "A simple and accurate discontinuous Galerkin scheme for modeling scalar-wave propagation in media with curved interfaces". GEOPHYSICS 80, n.º 2 (1 de marzo de 2015): T83—T89. http://dx.doi.org/10.1190/geo2014-0164.1.
Resumen
Conventional high-order discontinuous Galerkin (DG) schemes suffer from interface errors caused by the misalignment between straight-sided elements and curved material interfaces. We have developed a novel DG scheme to reduce those errors. Our new scheme uses the correct normal vectors to the curved interfaces, whereas the conventional scheme uses the normal vectors to the element edge. We modify the numerical fluxes to account for the curved interface. Our numerical modeling examples demonstrate that our new discontinuous Galerkin scheme gives errors with much smaller magnitudes compared with the conventional scheme, although both schemes have second-order convergence. Moreover, our method significantly suppresses the spurious diffractions seen in the results obtained using the conventional scheme. The computational cost of our scheme is similar to that of the conventional scheme. The new DG scheme we developed is, thus, particularly useful for large-scale scalar-wave modeling involving complex subsurface structures.
46
Dahl, M., C. P. Dunning y T. Green. "Convective Transport of Chemicals across a Sediment-Water Interface". Water Science and Technology 28, n.º 8-9 (1 de octubre de 1993): 209–13. http://dx.doi.org/10.2166/wst.1993.0620.
Resumen
The transport of dissolved chemicals across a horizontal interface between surface water and a saturated porous medium, associated with an unstable density gradient across the interface, is studied experimentally. Particular attention is paid to the starting conditions (i.e. the rate at which the density difference increases), and to the effect of changes in the density difference once the convective flow pattern has been established. The goal is a general flux law for any time variation of the density difference. Three significant observations are discussed. First, greater masses added to the overlying water results in larger density instabilities that drive greater fluxes. Second, the rate of addition of the mass affects both the peak density gradient and the long-term flux across the interface. Slower rates of addition result in greater variability in the resulting flux. Third, throughout all experiments, the ratios of final fluxes for different masses are similar, regardless of addition time.
47
Rifaat, Ahmed, Hoda Ahdy y Manal Saadawy. "Metal Fluxes Across Sediment-Water Interface in Lake Qarun, Egypt". Journal of King Abdulaziz University-Earth Sciences 23, n.º 2 (2012): 87–100. http://dx.doi.org/10.4197/ear.23-2.5.
48
Baeyens, W., M. Leermakers, H. Dedeurwaerder y P. Lansens. "Modelization of the mercury fluxes at the air-sea interface". Water Air & Soil Pollution 56, n.º 1 (abril de 1991): 731–44. http://dx.doi.org/10.1007/bf00342313.
49
Grossi, G. y L. Falappi. "Comparison of energy fluxes at the land surface-atmosphere interface in an Alpine valley as simulated with different models". Hydrology and Earth System Sciences 7, n.º 6 (31 de diciembre de 2003): 920–36. http://dx.doi.org/10.5194/hess-7-920-2003.
Resumen
Abstract. Within the framework of a research project coupling meteorological and hydrological models in mountainous areas a distributed Snow-Soil-Vegetation-Atmosphere Transfer model was developed and applied to simulate the energy fluxes at the land surface – atmosphere interface in an Alpine valley (Toce Valley - North Italy) during selected flood events in the last decade. Energy fluxes simulated by the distributed energy transfer model were compared with those simulated by a limited area meteorological model for the event of June 1997 and the differences in the spatial and temporal distribution. The Snow/Soil-Vegetation-Atmosphere Transfer model was also applied to simulate the energy fluxes at the land surface-atmosphere interface for a single cell, assumed to be representative of the Siberia site (Toce Valley), where a micro-meteorological station was installed and operated for 2.5 months in autumn 1999. The Siberia site is very close to the Nosere site, where a standard meteorological station was measuring precipitation, air temperature and humidity, global and net radiation and wind speed during the same special observing period. Data recorded by the standard meteorological station were used to force the energy transfer model and simulate the point energy fluxes at the Siberia site, while turbulent fluxes observed at the Siberia site were used to derive the latent heat flux from the energy balance equation. Finally, the hourly evapotranspiration flux computed by this procedure was compared to the evapotranspiration flux simulated by the energy transfer model. Keywords: energy exchange processes, land surface-atmosphere interactions, turbulent fluxes
50
Socolowsky, Jürgen. "On a viscous two-fluid channel flow including evaporation". Open Mathematics 16, n.º 1 (31 de enero de 2018): 9–15. http://dx.doi.org/10.1515/math-2018-0001.
Resumen
AbstractIn this contribution a particular plane steady-state channel flow including evaporation effects is investigated from analytical point of view. The channel is assumed to be horizontal. The motion of two heavy viscous immiscible fluids is governed by a free boundary value problem for a coupled system of Navier-Stokes and Stephan equations. The flow domain is unbounded in two directions and the free interface separating partially both liquids is semi-infinite, i.e. infinite in one direction. The free interface begins in some point Q where the half-line Σ1 separating the two parts of the channel in front of Q ends. Existence and uniqueness of a suitable solution in weighted HÖLDER spaces can be proved for small data (i.e. small fluxes) of the problem.