Nanomechanics: Small-Scale Coarse-Grained Models

2017 ◽  
pp. 447-501
Keyword(s):  
Coarse Grained ◽  
Small Scale

The late Miocene eolian record at the eastern margin of the Puna Plateau, NW Argentina: Evidence of upper-tropospheric paleocirculation

2022 ◽  
Vol 92 (1) ◽  
pp. 32-49
Author(s):  
Jonathan Ledesma ◽  
Cecilia E. Del Papa ◽  
Patricio Payrola
Keyword(s):  
Atmospheric Circulation ◽  
Late Miocene ◽  
Amazon Basin ◽  
Coarse Grained ◽  
Small Scale ◽  
Provenance Analysis ◽  
Humid Climate ◽  
Upper Troposphere ◽  
Facies Associations ◽  
Puna Plateau

Abstract The Puna–Altiplano Plateau of the Central Andes is the second-highest plateau in the world (after Tibet), with a mean elevation of 4000 m.a.s.l. and an arid to hyperarid climate. Uplift of the Puna–Altiplano Plateau has affected lower-level atmospheric circulation, acting as a barrier to humid easterly winds from the Amazon basin and favoring an across-strike precipitation gradient resulting in a humid climate towards the east of the plateau and an arid to hyperarid climate in the orogen's interior. In the modern climate, the Bolivian High anticyclone regulates upper troposphere circulation, but little is known about the high-altitude tropospheric circulation of the past. This work focuses on the eolian record of the San Antonio de los Cobres basin along the eastern border of the Puna Plateau, NW Argentina, with the aim of analyzing its origin and thus elucidating the late Miocene winds. The eolian deposits are constrained by 7.8 Ma (K/Ar and U/Pb) and 6.4 Ma (U/Pb) ignimbrites at the nearly basal and upper contacts, respectively. Based on stratigraphic, sedimentological, and provenance analysis of the eolian units, we have identified three main facies associations (FAs): FA1) cross-stratified sandstones with large- to small-scale tabular, planar cross-bedding and with trough cross-stratification; FA2) sandstones with planar to low-angle stratification associated with thinly laminated ripple sandstone strata; FA3) medium- to coarse-grained massive sandstones associated with pebbly to bouldery, matrix-supported conglomerates and clast-supported conglomerates. The lateral and vertical facies assemblages indicate a dune field confined to topographic depressions dominated by transverse dunes with straight and sinuous crestlines that laterally grade into sandsheets associated with ephemeral streams. Paleoflows, lithotypes, and grain-size determinations indicate a persistent north-northwest provenance and wind velocities of 24–38 km/h (with maximum velocities of 55–75 km/h). The results of our analysis coupled with data from previous studies indicates that, for at least the last ca. 8 Myr, the winds have been blowing constantly from the north-northwest with an intensity similar to the present. This implies that the paleo-atmospheric circulation had a similar pattern to the present-day one. Therefore, we conclude that the upper-troposphere circulation in the Puna Plateau of NW Argentina was already regulated by the Bolivian High anticyclone during the Miocene, generating constant north-northwesterly winds.

scholarly journals Short-scale variability of the SCLM beneath the extra-Andean back-arc (Paso de Indios, Argentina): Evidence from spinel-facies mantle xenoliths

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Alexis D. Ponce ◽  
Gustavo W. Bertotto ◽  
Alberto Zanetti ◽  
Daniele Brunelli ◽  
Tommaso Giovanardi ◽  
...  
Keyword(s):  
Partial Melting ◽  
Open System ◽  
Mantle Xenoliths ◽  
Coarse Grained ◽  
Small Scale ◽  
Host Basalt ◽  
Cenozoic Era ◽  
The Common ◽  
Back Arc ◽  
Reaction Schemes

AbstractCenozoic basalts carrying ultramafic mantle xenoliths occur in the Matilde, León and Chenque hills in the Paso de Indios region, Argentina. The mantle xenoliths from the Chenque and León hills mainly present porphyroclastic textures, whereas the Matilde hill xenoliths have coarse-grained to porphyroclastic textures. The equilibrium temperatures are in the range of 780 to 940ºC, indicating a provenance from shallow sectors of the lithospheric mantle column that were subjected to a relatively low heat ffiux at Cenozoic Era.According to the modal compositions of xenoliths, the mantle beneath Matilde and León hills was affected by greater than 22% partial melting, while less depleted peridotites occur in the Chenque suite (starting from 10% partial melting). Such an observation is confirmed by the partial melting estimates based on Cr#Sp, which vary from 8 to 14% for the selected Chenque samples and from 14 to 18% for the Matilde ones.The common melting trend is overlapped by small-scale cross cutting local trends that may have been generated by open-system processes, such as open-system partial melting and/or post partial-melting metasomatic migration of exotic Na-Cr-rich melts.The two main mineralogical reaction schemes are: i) the dissolution of pyroxenes and the segregation of new olivine in olivine-rich peridotites, and ii) the replacement of primary olivine by orthopyroxene±clinopyroxene in orthopyroxene-rich peridotites. These were produced by channelled and/or pervasive melt extraction/ migration. Enhanced pyroxene dissolution is attributed to channelling of silica- undersaturated melts, whereas the replacement of primary olivine by orthopyroxene±clinopyroxene points to reaction with silica-saturated melts.Late disequilibrium reactions identified in the xenoliths comprise: the breakdown of orthopyroxene in contact with the host basalt, and (rarely) reaction coronae on orthopyroxene, clinopyroxene and spinel linked to glassy veins. Such features are apparently related to the injection of melt, likely during entrainment into the host basalts and ascent to the surface.

scholarly journals The impact of inhomogeneous subgrid clumping on cosmic reionization

2019 ◽  
Vol 491 (2) ◽  
pp. 1600-1621
Author(s):  
Yi Mao ◽  
Jun Koda ◽  
Paul R Shapiro ◽  
Ilian T Iliev ◽  
Garrelt Mellema ◽  
...  
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Power Spectra ◽  
Coarse Grained ◽  
Small Scale ◽  
Sources And Sinks ◽  
Coarse Grained Simulations ◽  
Cent Error ◽  
Spatially Varying ◽  
The Impact

ABSTRACT Cosmic reionization was driven by the imbalance between early sources and sinks of ionizing radiation, both of which were dominated by small-scale structure and are thus usually treated in cosmological reionization simulations by subgrid modelling. The recombination rate of intergalactic hydrogen is customarily boosted by a subgrid clumping factor, 〈n2〉/〈n〉2, which corrects for unresolved fluctuations in gas density n on scales below the grid-spacing of coarse-grained simulations. We investigate in detail the impact of this inhomogeneous subgrid clumping on reionization and its observables, as follows: (1) Previous attempts generally underestimated the clumping factor because of insufficient mass resolution. We perform a high-resolution N-body simulation that resolves haloes down to the pre-reionization Jeans mass to derive the time-dependent, spatially varying local clumping factor and a fitting formula for its correlation with local overdensity. (2) We then perform a large-scale N-body and radiative transfer simulation that accounts for this inhomogeneous subgrid clumping by applying this clumping factor-overdensity correlation. Boosting recombination significantly slows the expansion of ionized regions, which delays completion of reionization and suppresses 21 cm power spectra on large scales in the later stages of reionization. (3) We also consider a simplified prescription in which the globally averaged, time-evolving clumping factor from the same high-resolution N-body simulation is applied uniformly to all cells in the reionization simulation, instead. Observables computed with this model agree fairly well with those from the inhomogeneous clumping model, e.g. predicting 21 cm power spectra to within 20 per cent error, suggesting it may be a useful approximation.

Multi-scale hydrogeologic characterization of a leaky till–mantled fractured bedrock aquifer system

2015 ◽  
Vol 52 (12) ◽  
pp. 1945-1955 ◽  
Author(s):  
William G. Lukas ◽  
Don J. DeGroot ◽  
David W. Ostendorf ◽  
Erich S. Hinlein
Keyword(s):  
Hydraulic Conductivity ◽  
Coarse Grained ◽  
Small Scale ◽  
Data Sets ◽  
Aquifer System ◽  
Monitoring Wells ◽  
Fractured Bedrock ◽  
Decadal Scale ◽  
Fractured Bedrock Aquifer ◽  
Bedrock Aquifer

The paper presents hydrogeologic properties for a leaky till–mantled fractured bedrock aquifer system based on geophysical and hydraulic tests performed at a drumlin located in northeastern Massachusetts, USA. The site profile consists of a fractured bedrock aquifer overlain by a 30 m thick unweathered, coarse-grained till aquitard. Steady state, decadal scale, hydraulics varied little until seasonal irrigation pumping was initiated in recent years, causing a substantial annual drawdown in the aquifer and leakage from the overlying till. High frequency hydraulic head data sets collected in monitoring wells record the hydraulic response to the irrigation pumping. These data sets, together with results from small scale slug and purge tests performed in monitoring wells, are used to characterize the hydrogeologic behavior of this groundwater system. Geophysical logging performed in bedrock wells confirmed the presence of numerous flowing fractures. The large-scale continuum analysis of the fractured bedrock aquifer response to the irrigation pumping yields transmissivity values consistent with those determined from the small-scale, short-term purge test results. The low hydraulic conductivity till has a significant impact on the drawdown behavior of the fractured bedrock aquifer. Calibrated values from the collective data sets and analyses result in the following properties for the 30 m thick unweathered till: hydraulic conductivity K′ = 7.2 × 10−9 m/s, transmissivity T′ = 2.3 × 10−8 m2/s, and storativity S′ = 2.7 × 10−4, and for the underlying fractured bedrock aquifer: T = 6.5 × 10−6 m2/s with an average fracture aperture of 46 μm and hydraulic conductivity Kf = 1.3 × 10−3 m/s. These results should describe similar unweathered coarse-grained till–mantled fractured bedrock aquifer systems and provide useful data for preliminary analyses prior to any site-specific investigations.

Bed configuration and microscale processes in alluvial channels

1993 ◽  
Vol 17 (2) ◽  
pp. 123-136 ◽  
Author(s):  
André Robert
Keyword(s):  
Probabilistic Approach ◽  
Field Measurements ◽  
Bedload Transport ◽  
Transport Processes ◽  
Coarse Grained ◽  
Small Scale ◽  
Alluvial Channels ◽  
Gravel Beds ◽  
Sand And Gravel ◽  
Bed Material

Numerous recent studies on fluvial processes, both in Canada and internationally, have focused on small-scale phenomena. Investigations on the characterization of surface roughness in coarse-grained channels and its links with flow resistance and sediment transport processes have been a dominant field of research. Closely related is a second major area of investigation on turbulent flow structures in boundary layers over both sand and gravel beds and their relations with the transport of bed material. Phenomena potentially related to 'bursting' have been shown to control bedload transport processes and the concentration of sediment in suspension. Detailed investigations have also been conducted on the links between flow turbulence, bed material movement, and bed morphology at channel junctions. Finally, selective entrainment and transport of individual coarse particles have been studied from field measurements and laboratory experi ments. Emphasis has been put on bed microtopography, surface structure and texture, and on a probabilistic approach to bedload transport.

Numerical simulation of turbulent thermal convection based on LBM

2020 ◽  
pp. 2150070
Author(s):  
Yuxian Xia ◽  
Yuan Fu ◽  
Jiahua Li ◽  
Xiang Qiu ◽  
Yuehong Qian ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Thermal Convection ◽  
Large Scale ◽  
Coarse Grained ◽  
Field Energy ◽  
Small Scale ◽  
Temperature Spectrum ◽  
Full Field ◽  
Scale Range ◽  
Boltzmann Method

The two-dimensional (2D) turbulent thermal convection is numerically investigated by using Lattice Boltzmann Method. The 2D turbulence is considered as 2D channel flow where the flow is forced by the arrays of adiabatic cylinders placed in the inlet and wall boundary of 2D channel, which is heated uniformly from the inlet as to inspire the paradigmatic motion of thermal convection. It is found that the spacing vortex number density distribution in the large-scale range [Formula: see text], based on the Liutex vortex definition criterion, which is in fair agreement with the Benzi prediction. The energy spectrum of the Liutex field [Formula: see text]. The scaling behavior of full-field energy spectrum in the large scale is [Formula: see text]. The temperature spectrum in the large-scale range is found to be approximate to [Formula: see text], which is according with the Bolgiano theory of 2D buoyancy driven turbulence. The energy flux cascades to the large scale, the enstrophy cascades to small scale. The moments of the energy dissipation field [Formula: see text] coarse grained at the scale [Formula: see text] have the power-law behaviors with the scale [Formula: see text]. The velocity intermittency measured by PDF exists in large-scale range of 2D turbulent thermal convection. The measured scaling exponents [Formula: see text] are determined by a lognormal formula. The measured intermittency parameter is [Formula: see text], which denotes the strong intermittency in the large-scale range of 2D turbulent thermal convection.

Introduction To Renormalization Group Modeling Of Turbulence

1996 ◽  
Author(s):  
Steven A. Orszag ◽  
I. Staroselsky,
Keyword(s):  
Renormalization Group ◽  
Turbulent Flows ◽  
Equations Of Motion ◽  
Turbulence Models ◽  
Coarse Grained ◽  
Small Scale ◽  
Flow Problems ◽  
Group Modeling ◽  
Systematic Derivation ◽  
Incompressible Turbulence

The renormalization group (RNG) and related e-expansion methods are a powerful technique that allow the systematic derivation of coarse-grained equations of motion for turbulent flows and, in particular, the derivation of sophisticated turbulence models based on the fundamental underlying physics. The RNG method provides a convenient calculus for the analysis of complex physical effects in complex flows. The details of the RNG method applied to fluid mechanics differ in some crucial respects from how renormalization group techniques are applied to field theories in other branches of physics. At the present time, the RNG methods for fluid dynamics are by no means rigorously justified, so their utility must be based on the quality and quantity of results to which they lead. In this paper we discuss the basis for the RNG method and then illustrate its application to a variety of turbulent flow problems, emphasizing those points where further analysis is needed. The application of a field-theoretic method like the RNG technique to turbulence is based on the fundamental assumption of universality of small scales in turbulent flows. Such universal behavior was first suggested over 50 years ago in the seminal work of A. N. Kolmogorov who argued that the small-scale spectrum of incompressible turbulence is universal and characterized by two numbers, the rate of energy dissipation ε per unit mass and the kinematic viscosity v.

scholarly journals Integrated Laser-Induced Breakdown Spectroscopy (LIBS) and Multivariate Wavelet Tessellation: A New, Rapid Approach for Lithogeochemical Analysis and Interpretation

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 312
Author(s):  
Fernando F. Fontana ◽  
Steven Tassios ◽  
Jessica Stromberg ◽  
Caroline Tiddy ◽  
Ben van der Hoek ◽  
...  
Keyword(s):  
Rock Block ◽  
Coarse Grained ◽  
Geochemical Data ◽  
Laser Induced Breakdown Spectroscopy ◽  
Small Scale ◽  
Breakdown Spectroscopy ◽  
Novel Approach ◽  
Laser Induced Breakdown ◽  
Mineral Compositions ◽  
Plutonic Rocks

This paper demonstrates a novel approach that uses wavelet tessellation in rapid analysis of raw geochemical data produced by laser-induced breakdown spectroscopy (LIBS) to produce pseudologs that are representative of stratigraphy. Single-line LIBS spectral data for seven major rock-forming elements (Al, Ca, Fe, Mg, Si, Na and K) were collected from a synthetic 22-sample rock-block comprising two distinct lithological groups based on mineralogy, chemistry and texture: plutonic rocks and marble. Seven sublithologies are identified within the rock-block from traditional laboratory whole-rock geochemical analysis: marble, Mg-marble, granite, quartz monzonite, foidolite, granodiorite and gabbroic diorite. Two-domain clustering (k = 2) on raw spectral LIBS data combined with wavelet tessellation was applied to generate a simplified lithological stratigraphy of marble and plutonic rocks and generate a pseudolog identical to the rock-block stratigraphy. A pseudolog generated from seven-domain clustering (k = 7) and wavelet tessellation successfully discriminated most sublithologies within the rock-block slabs, especially marble slabs. Small-scale units were identified within the more mineralogically and geochemically complex plutonic slabs. The spatial resolution of the LIBS analysis, with a measurement spacing of ~0.35 mm, allowed for assessment of individual mineral compositions and rock textures, and small-scale units within the plutonic rocks can be correlated to specific coarse-grained minerals or mineralogical associations. The application of the wavelet tessellation method to raw LIBS geochemical data offers the possibility of rapid and objective lithogeochemical analysis and interpretations which can predate further analysis (quantitative) and supplement geological logging.

scholarly journals Stochastic modeling of the oceanic mesoscale eddies

2021 ◽  
Author(s):  
Long Li ◽  
Bruno Deremble ◽  
Noé Lahaye ◽  
Etienne Mémin
Keyword(s):  
Large Scale ◽  
Mesoscale Eddy ◽  
Low Frequency ◽  
Stochastic Approach ◽  
Coarse Grained ◽  
Small Scale ◽  
Oceanic Circulation ◽  
Stochastic Representation ◽  
Stochastic Framework ◽  
Gyre Circulation

<p>In this work, a stochastic representation [Bauer2020a, Bauer2020b] based on a physical transport principle is proposed to account for mesoscale eddy effects on the the large-scale oceanic circulation. This stochastic framework [Mémin2014] arises from a decomposition of the Lagrangian velocity into a time-smooth component and a highly oscillating noise term. One important characteristic of this random model is that it conserves the energy of any transported tracer. Such an energy-preserving representation has been successfully implemented in a well established multi-layered quasi-geostrophic dynamical core (http://www.q-gcm.org). The empirical spatial correlation of the small-scale noise is estimated from the eddy-resolving simulation data. In particular, a sub-grid correction drift has been introduced in the noise due to the bias ensuing from the coarse-grained procedure. This non intuitive term seems quite important in reproducing on a coarse mesh the meandering jet of the wind-driven double-gyre circulation. In addition, a new projection method has been proposed to constrain the noise living along the iso-surfaces of the vertical stratification. The resulting noise enables us to improve the intrinsic low-frequency variability of the large-scale current. From some statistical studies and energy transfers analysis, this improvement is well demonstrated.</p><ul><li><span>[</span>Bauer2020a] W. Bauer, P. Chandramouli, B. Chapron, L. Li, and E. Mémin. Deciphering the role of small-scale inhomogeneity on geophysical flow structuration: a stochastic approach. Journal of Physical Oceanography, 50(4):983-1003, 2020a.<span>       </span></li> <li><span>[</span>Bauer2020b] W. Bauer, P. Chandramouli, L. Li, and E. Mémin. Stochastic representation of mesoscale eddy effects in coarse-resolution barotropic models. Ocean Modelling, 151:101646 (2020b). <span>   </span></li> <li>[Mémin2014] E. Mémin. Fluid flow dynamics under location uncertainty. Geophysical & Astrophysical Fluid Dynamics, 108(2):119-146, 2014.<span>     </span></li> </ul>

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