scholarly journals Impact of convection on the damping of an oscillating droplet during viscosity measurement using the ISS-EML facility

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Xiao Xiao ◽  
Jürgen Brillo ◽  
Jonghyun Lee ◽  
Robert W. Hyers ◽  
Douglas M. Matson
Keyword(s):  
Effective Viscosity ◽  
Domain Size ◽  
Electromagnetic Levitation ◽  
Viscosity Measurement ◽  
Pulse Excitation ◽  
Damping Behavior ◽  
Damping Rate ◽  
Decay Pattern ◽  
Microgravity Conditions ◽  
The Impact

AbstractOscillating droplet experiments are conducted using the Electromagnetic Levitation (EML) facility under microgravity conditions. The droplet of molten metal is internally stirred concurrently with the pulse excitation initiating shape oscillations, allowing viscosity measurement of the liquid melts based on the damping rate of the oscillating droplet. We experimentally investigate the impact of convection on the droplet’s damping behavior. The effective viscosity arises and increases as the internal convective flow becomes transitional or turbulent, up to 2–8 times higher than the intrinsic molecular viscosity. The enhanced effective viscosity decays when the stirring has stopped, and an overshoot decay pattern is identified at higher Reynolds numbers, which presents a faster decay rate as the constraint of flow domain size becomes influential. By discriminating the impact of convection on the viscosity results, the intrinsic viscosity can be evaluated with improved measurement accuracy.

The importance of phase morphology for rheology of ferropericlase-bridgmanite mixtures

2021 ◽  
Author(s):  
Marcel Thielmann ◽  
Gregor Golabek ◽  
Hauke Marquardt
Keyword(s):  
Lower Mantle ◽  
Mantle Convection ◽  
Effective Viscosity ◽  
Large Scale ◽  
Numerical Models ◽  
Phase Morphology ◽  
Strong Impact ◽  
Analytical Approximations ◽  
The Impact ◽  
Strong Control

<p>The rheology of the Earth’s lower mantle is poorly constrained due to a lack of knowledge of the rheological behaviour of its constituent minerals. In addition, the lower mantle does not consist of only a single, but of multiple mineral phases with differing deformation behaviour. The rheology of Earth’s lower mantle is thus not only controlled by the rheology of its individual constituents (bridgmanite and ferropericlase), but also by their interplay during deformation. This is particularly important when the viscosity contrast between the different minerals is large. Experimental studies have shown that ferropericlase may be significantly weaker than bridgmanite and may thus exert a strong control on lower mantle rheology.</p><p>Here, we thus explore the impact of phase morphology on the rheology of a ferropericlase-bridgmanite mixture using numerical models. We find that elongated ferropericlase structures within the bridgmanite matrix significantly lower the effective viscosity, even in cases where no interconnected network of weak ferropericlase layers has been formed. In addition to the weakening, elongated ferropericlase layers result in a strong viscous anisotropy. Both of these effects may have a strong impact on lower mantle dynamics, which makes is necessary to develop upscaling methods to include them in large-scale mantle convection models. We develop a numerical-statistial approach to link the statistical properties of a ferropericlase-bridgmanite mixture to its effective viscosity tensor. With this approach, both effects are captured by analytical approximations that have been derived to describe the evolution of the effective viscosity (and its anisotropy) of a two-phase medium with aligned elliptical inclusions, thus allowing to include these microscale processes in large-scale mantle convection models.</p>

scholarly journals WRF Hindcasts of Cold Front Passages over the ARM Eastern North Atlantic Site: A Sensitivity Study

2018 ◽  
Vol 146 (8) ◽  
pp. 2417-2432 ◽  
Author(s):  
Fayçal Lamraoui ◽  
James F. Booth ◽  
Catherine M. Naud
Keyword(s):  
Case Studies ◽  
North Atlantic ◽  
Cold Front ◽  
Domain Boundary ◽  
Wrf Model ◽  
Domain Size ◽  
Sensitivity Study ◽  
Spectral Nudging ◽  
Eastern North Atlantic ◽  
The Impact

Abstract The present study explores the ability of the Weather Research and Forecasting (WRF) Model to accurately reproduce the passage of extratropical cold fronts at the DOE ARM eastern North Atlantic (ENA) observation site on the Azores. An analysis of three case studies is performed in which the impact of the WRF domain size, position of the model boundary relative to the ENA site, grid spacing, and spectral nudging conditions are explored. The results from these case studies indicate that model biases in the timing and duration of cold front passages change with the distance between the model domain boundary and the ENA site. For these three cases, if the western model boundary is farther than 1500 km from the site, the front becomes too meridional and fails to reach the site, making 1000 or 1500 km the optimal distances. In contrast, integrations with small distances (e.g., 500 km) between the site and domain boundaries have inadequate spatial spinup (i.e., the domain is too small for the model to properly stabilize). For all three cases, regardless of domain size, the model has biases in its upper-level circulation that impact the position and timing of the front. However, this issue is most serious for 4000-km2 domains and larger. For these domains, prolonged spectral nudging can correct cold front biases. As such, this analysis provides a framework to optimize the WRF Model configuration necessary for a realistic hindcast of a cold front passage at a fixed location centered in a domain as large as computationally possible.

scholarly journals One-Way Nested Regional Climate Simulations and Domain Size

2005 ◽  
Vol 18 (1) ◽  
pp. 229-233 ◽  
Author(s):  
S. Vannitsem ◽  
F. Chomé
Keyword(s):  
Western Europe ◽  
State Of The Art ◽  
Regional Climate ◽  
Domain Size ◽  
Regional Model ◽  
Dynamical Behaviors ◽  
Climate Simulations ◽  
Intermediate Size ◽  
The Impact

Abstract The impact of domain size on regional climate simulations is explored in the context of a state-of-the-art regional model centered over western Europe. It is found that the quality of the climate simulations is highly dependent on the domain size. Moreover, the choice of an optimal version is more complex than usually thought, the less appropriate domain having an intermediate size (about 3000 km × 3000 km), and the best versions nearly cover a quarter of the Northern Hemisphere. The use of periodically reinitialized trajectories does improve the climate of suboptimal models but leads to unrealistic dynamical behaviors. The implications for regional climate simulations are briefly discussed.

scholarly journals Graded Morphologies and the Performance of PffBT4T-2OD:PC71BM Devices Using Additive Choice

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3367
Author(s):  
Hugo Gaspar ◽  
Andrew J. Parnell ◽  
Gabriel E. Pérez ◽  
Júlio C. Viana ◽  
Stephen M. King ◽  
...  
Keyword(s):  
Power Conversion Efficiency ◽  
Organic Semiconductors ◽  
Conversion Efficiency ◽  
Polymer Solar Cells ◽  
Power Conversion ◽  
Acid Methyl Ester ◽  
Domain Size ◽  
Grazing Incidence ◽  
Exciton Diffusion Length ◽  
The Impact

The impact of several solvent processing additives (1-chloronaphthalene, methylnaphthalene, hexadecane, 1-phenyloctane, and p-anisaldehyde), 3% v/v in o-dichlorobenzene, on the performance and morphology of poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di(2-octyldodecyl)-2,2′,5′,22033,5″,2‴-quaterthiophen-5,5‴-diyl)] (PffBT4T-2OD):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM)-based polymer solar cells was investigated. Some additives were shown to enhance the power conversion efficiency (PCE) by ~6%, while others decreased the PCE by ~17–25% and a subset of the additives tested completely eliminated any power conversion efficiency and the operation as a photovoltaic device. Grazing-Incidence Wide Angle X-ray Scattering (GIWAXS) revealed a clear stepwise variation in the crystallinity of the systems when changing the additive between the two extreme situations of maximum PCE (1-chloronaphthalene) and null PCE (hexadecane). Small-Angle Neutron Scattering (SANS) revealed that the morphology of devices with PCE ~0% was composed of large domains with correlation lengths of ~30 nm, i.e., much larger than the typical exciton diffusion length (~12 nm) in organic semiconductors. The graded variations in crystallinity and in nano-domain size observed between the two extreme situations (1-chloronaphthalene and hexadecane) were responsible for the observed graded variations in device performance.

scholarly journals Issues in Simulating the Annual Precipitation of a Semiarid Region in Central Spain

2005 ◽  
Vol 6 (4) ◽  
pp. 409-422 ◽  
Author(s):  
N. Hasler ◽  
R. Avissar ◽  
G. E. Liston
Keyword(s):  
High Resolution ◽  
Climate Models ◽  
Domain Size ◽  
Atmospheric Modeling ◽  
Annual Rainfall ◽  
Semiarid Region ◽  
Central Spain ◽  
Small Domain ◽  
The Impact ◽  
Dry Bias

Abstract Running regional climate models at a high resolution may improve their ability to simulate regional precipitation patterns, making them suitable for studying the impact of human-induced land-cover changes on hydrometeorology. The performance of the Regional Atmospheric Modeling System (RAMS) run in the high-resolution climate mode (4-km grid mesh) has been tested over a small domain in a semiarid region in central Spain. Three 1-yr simulations representing dry, intermediate, and wet conditions were compared to observations collected in 35 rain gauges. The model captured general spatiotemporal features of precipitation, such as the timing of precipitation events and approximate location of storms. A high correlation (0.82) between monthly domain-averaged observed and modeled precipitation was obtained. However, the model had a systematic dry bias, averaging −0.29 mm day−1, equivalent to 26% of annual rainfall. The small domain size, chosen because of computational limits, induced strong lateral boundary forcing, which, combined with uncertainty in NCEP relative humidity fields, was a likely cause for this dry bias.

Analysis of Non-Classical Models which Have been Subjected to Percussive Loads Using Equations of Energy and Power

2014 ◽  
Vol 1036 ◽  
pp. 608-613 ◽  
Author(s):  
Krzysztof Jamroziak ◽  
Miroslaw Bocian
Keyword(s):  
Energy Dissipation ◽  
Impact Energy ◽  
Dynamic Models ◽  
Specific Impulse ◽  
Pulse Excitation ◽  
Classical Dynamic ◽  
Simple Description ◽  
Classical Models ◽  
The One ◽  
The Impact

The article presents an analysis of impact energy dissipation process with selected non-classical dynamic models. Identification of impact energy dissipation phenomena in layered mechanical systems (for example: composite ballistic shields) is a great challenge, because on the one hand a model with parameters responsible for the energy dissipation is being sought on the one hand and on the other it is necessary to optimise the number of parameters. The sought model should be reduced to a simple description of the phenomenon and should contain a complex reproduction of the whole mechanical system. In this case the impact energy dissipation was described using selected degenerate systems. Models were treated by extortion surge having a specific impulse of force. The mathematical description of the pulse excitation was carried out using the energy and potency balance equations. The verification of mathematical identification equations was conducted using a computer simulation technique for the selected model’s parameters.

The Impact of Background Function on High Accuracy Quantitative Rietveld Analysis (QRA): Application to NIST SRMs 676 and 656

1994 ◽  
Vol 38 ◽  
pp. 59-68
Author(s):  
Robert B. Von Dreele ◽  
James. P. Cline
Keyword(s):  
Particle Size ◽  
Quantitative Analysis ◽  
Quantitative Result ◽  
Domain Size ◽  
Silicon Powder ◽  
Rietveld Analysis ◽  
Alumina Powder ◽  
Laser Scattering ◽  
Amorphous Content ◽  
The Impact

Abstract The accuracy of Quantitative Rietveid Analysis (QRA) was examined in terms of the plausibility of the set of refined parameters as well as the realization of the expected quantitative result. This route was pursued due to the two mutually exclusive characteristics that a powder exhibiting the calculated (ideal) diffraction intensity would possess; it would have infinitesimal domains to alleviate the effects of extinction but at the same time infinitesimal surface area to eliminate the volume of the disordered surface or amorphous phase. The specimens were mixtures of NIST Standard Reference Material (SRM) 640b, a silicon powder with a mean particle size of 7 pin (certified with respect to lattice parameters), and SRM 676, an alumina powder with a submicrometer crystallite size (certified for quantitative analysis). Good agreement between the particle size of SRM 640b, determined by laser scattering measurements, and its domain size, determined by using the Sabine model for extinction, were obtained with the use of improved background functions in refinements of neutron time-of-flight (TOF) powder diffraction data. These data, in conjunction with the plausibility of other refined parameters such as temperature factors, led to a credible measurement of the amorphous content of SRM 676 and a verification that TOF data can yield unbiased quantitative results. A new SRM for quantitative analysis of silicon nitride was certified with respect to the a, p and amorphous (impurity) phase content with the use of TOF diffraction and SRM 676 as the reference phase. Results from XRD data were found to be less sensitive to background function, though improvements in the Rietveid analysis of XRD data were achieved.

scholarly journals History dependence and the continuum approximation breakdown: the impact of domain growth on Turing’s instability

2017 ◽  
Vol 473 (2199) ◽  
pp. 20160744 ◽  
Author(s):  
Václav Klika ◽  
Eamonn A. Gaffney
Keyword(s):  
Domain Size ◽  
Turing Instability ◽  
Domain Growth ◽  
Continuum Approximation ◽  
Growing Domain ◽  
Spatial Frequencies ◽  
History Of ◽  
The Stability ◽  
The Impact ◽  
The Continuum

A diffusively driven instability has been hypothesized as a mechanism to drive spatial self-organization in biological systems since the seminal work of Turing. Such systems are often considered on a growing domain, but traditional theoretical studies have only treated the domain size as a bifurcation parameter, neglecting the system non-autonomy. More recently, the conditions for a diffusively driven instability on a growing domain have been determined under stringent conditions, including slow growth, a restriction on the temporal interval over which the prospect of an instability can be considered and a neglect of the impact that time evolution has on the stability properties of the homogeneous reference state from which heterogeneity emerges. Here, we firstly relax this latter assumption and observe that the conditions for the Turing instability are much more complex and depend on the history of the system in general. We proceed to relax all the above constraints, making analytical progress by focusing on specific examples. With faster growth, instabilities can grow transiently and decay, making the prediction of a prospective Turing instability much more difficult. In addition, arbitrarily high spatial frequencies can destabilize, in which case the continuum approximation is predicted to break down.

Sign in / Sign up

Export Citation Format

Share Document