scholarly journals Reconstructing spatially variable mass balances from past ice extents by inverse modeling

2018 ◽  
Vol 64 (248) ◽  
pp. 957-968 ◽  
Author(s):  
VJERAN VIŠNJEVIĆ ◽  
FRÉDÉRIC HERMAN ◽  
YURY PODLADCHIKOV
Keyword(s):  
Variable Mass ◽  
Mass Conservation ◽  
Conservation Equation ◽  
Inversion Method ◽  
Last Glacial ◽  
Ice Caps ◽  
Inverse Approach ◽  
Temperature And Precipitation ◽  
Geomorphic Features ◽  
Graphical Processing

ABSTRACTWith the conclusion of the Last Glacial Maximum (LGM), about 20 000 years ago, ended the most recent long-lasting cold phase in Earth history. This last glacial advance left a strong observable imprint on the landscape, such as moraines, trimlines and other glacial geomorphic features. These features reflect the extent of former glaciers and ice caps, which in turn provides information on past temperature and precipitation conditions. Here we present an inverse approach to reconstruct the equilibrium line altitudes (E) from observed ice extents. The ice-flow model is developed solving the mass conservation equation using the shallow ice approximation and implemented using Graphical Processing Units (GPUs). We present the theoretical basis of the inversion method, which relies on a Tikhonov regularization, and demonstrate its ability to constrain spatial variations in mass balance with idealized and real glaciers.

On a New Passive Scalar Equation With Variable Mass Diffusivity

2008 ◽  
Author(s):  
Fabio Gori ◽  
Andrea Boghi
Keyword(s):  
Mass Flux ◽  
Variable Mass ◽  
Mass Conservation ◽  
Passive Scalar ◽  
Conservation Equation ◽  
Average Concentration ◽  
Concentration Fluctuation ◽  
Mass Diffusivity ◽  
Coupled Solution ◽  
Mass Conservation Equation

The present work investigates the mass conservation equation of a Newtonian and non-Newtonian fluid in turbulent flow with variable mass diffusivity. The mass conservation equation is considered with the fluctuating terms in the concentration as well as in the mass diffusivity and is written for the average concentration, for the fluctuating concentration one as well as for the square of the fluctuating concentration. A new term appears in the form of product of the fluctuating mass diffusivity to the space gradient of the concentration fluctuation. This new term is interpreted and introduced in the mass conservation equation of the square of the fluctuating concentration where other new terms are also appearing. A possible physical interpretation is given to the different terms. Assuming several relations between mass diffusivity and concentration it is then possible to write expressions for the average and the fluctuating mass concentration which can be simplified on the basis of physical and mathematical considerations. Specifically, the mass flux is then expressed as the product of the derivative of the mass diffusivity to the gradient of the square of the mass fluctuation. Further considerations make possible to write a new mass conservation equation of the average concentration which include a new term which takes into account the space gradient of the mass flux. The mass conservation equation can be solved with the coupled solution of the equation of the square of the concentration fluctuation.

On a New Passive Scalar Equation With Variable Mass Diffusivity: Flow Between Parallel Plates

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Fabio Gori ◽  
Andrea Boghi
Keyword(s):  
Variable Mass ◽  
Species Conservation ◽  
Mass Conservation ◽  
Passive Scalar ◽  
Conservation Equation ◽  
Average Concentration ◽  
Parallel Plates ◽  
Conservation Equations ◽  
Concentration Variance ◽  
Mass Diffusivity

The present work investigates mass conservation equations in turbulent flow between parallel plates with variable mass diffusivity. Species conservation equations are relative to the average concentration, as well as to the concentration variance. The product of fluctuating mass diffusivity and space gradient of concentration fluctuation is appearing in the equation of mean and concentration variance. A physical interpretation is given to the different terms. The assumption of a relation between mass diffusivity and concentration allows writing expressions for average and fluctuating mass diffusivity, which can be simplified on the basis of theoretical considerations. The new mass flux is expressed as a function of mass diffusivity and a gradient of concentration variance. Further considerations make it possible to model the new terms appearing in the concentration variance equation. The mass conservation equation can be solved when coupled to the equation of concentration variance. The equations are solved numerically for flow between parallel plates in order to evaluate the influence of the new terms.

Transport of Microorganisms in the Underground – Processes, Experiments and Simulation Models

1991 ◽  
Vol 24 (2) ◽  
pp. 309-314 ◽  
Author(s):  
G. Teutsch ◽  
K. Herbold-Paschke ◽  
D. Tougianidou ◽  
T. Hahn ◽  
K. Botzenhart
Keyword(s):  
Simulation Models ◽  
Mass Conservation ◽  
Breakthrough Curves ◽  
Conservation Equation ◽  
Retardation Factor ◽  
Natural Systems ◽  
Laboratory Setup ◽  
Preliminary Model ◽  
Sand And Gravel ◽  
Mass Conservation Equation

In this paper the major processes governing the persistence and underground transport of viruses and bacteria are reviewed in respect to their importance under naturally occurring conditions. In general, the simulation of the governing processes is based on the macroscopic mass-conservation equation with the addition of some filter and/or retardation factor and a decay coefficient, representing the natural “die-off” of the microorganisms. More advanced concepts try to incorporate growth and decay coefficients together with deposition and declogging factors. At present, none of the reported concepts has been seriously validated. Due to the complexity of natural systems and the pathogenic properties of some of the microorganisms, experiments under controlled laboratory conditions are required. A laboratory setup is presented in which a great variety of natural conditions can be simulated. This comprises a set of 1 metre columns and an 8 metre stainless-steel flume with 24 sampling ports. The columns are easily filled and conditioned and therefore used to study the effects of different soil-microorganism combinations under various environmental conditions. In the artificial flume natural underground conditions are simulated using sand and gravel aquifer material from the river Neckar alluvium. A first set of results from the laboratory experiments is presented together with preliminary model simulations. The large variety of observed breakthrough curves and recovery for the bacteria and viruses under investigation demonstrates the great uncertainty encountered in microbiological risk assessment.

scholarly journals Statistical downscaling of a climate simulation of the last glacial cycle: temperature and precipitation over Northern Europe

2014 ◽  
Vol 10 (4) ◽  
pp. 1489-1500 ◽  
Author(s):  
N. Korhonen ◽  
A. Venäläinen ◽  
H. Seppä ◽  
H. Järvinen
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Ice Sheet ◽  
Additive Models ◽  
Northern Europe ◽  
Glacial Cycle ◽  
Explanatory Variables ◽  
Last Glacial ◽  
Temperature And Precipitation ◽  
The Last Glacial

Abstract. Earth system models of intermediate complexity (EMICs) have proven to be able to simulate the large-scale features of glacial–interglacial climate evolution. For many climatic applications the spatial resolution of the EMICs' output is, however, too coarse, and downscaling methods are needed. In this study we introduce a way to use generalized additive models (GAMs) for downscaling the large-scale output of an EMIC in very different climatological conditions ranging from glacial periods to current relatively warm climates. GAMs are regression models in which a combination of explanatory variables is related to the response through a sum of spline functions. We calibrated the GAMs using observations of the recent past climate and the results of short time-slice simulations of glacial climate performed by the relatively high-resolution general circulation model CCSM (Community Climate System Model) and the regional climate model RCA3 (Rossby Centre regional Atmospheric climate model). As explanatory variables we used the output of a simulation by the CLIMBER-2 (CLIMate and BiosphERe model 2) EMIC of the last glacial cycle, coupled with the SICOPOLIS (SImulation COde for POLythermal Ice Sheets) ice sheet model, i.e. the large-scale temperature and precipitation data of CLIMBER-2, and the elevation, distance to ice sheet, slope direction and slope angle from SICOPOLIS. The fitted GAMs were able to explain more than 96% of the temperature response with a correlation of >0.98 and more than 59% of the precipitation response with a correlation of >0.72. The first comparison with two pollen-based reconstructions of temperature for Northern Europe showed that CLIMBER-2 data downscaled by GAMs corresponded better with the reconstructions than did the bilinearly interpolated CLIMBER-2 surface temperature.

A New Model for the Simulation of CO2 Absorption in an Industrial-Scale Packed Column

2012 ◽  
Vol 557-559 ◽  
pp. 2208-2216 ◽  
Author(s):  
Wen Bin Li ◽  
Guo Cong Yu ◽  
Bo Tan Liu ◽  
Xi Gang Yuan
Keyword(s):  
Mass Transfer ◽  
Packed Column ◽  
Mass Conservation ◽  
Conservation Equation ◽  
Industrial Scale ◽  
Transfer Model ◽  
Turbulent Heat ◽  
Proposed Model ◽  
Heat Conservation ◽  
Phase Temperature

A new computational mass transfer model is proposed for simulating the chemical absorption process with heat effect by solving the average fluctuating mass flux in turbulent mass conservation equation and the average fluctuating heat flux in turbulent heat conservation equation, so that the concentration profile and the temperature profile of column can be obtained. The feather of the proposed model is to abandon the conventional way of introducing the unknown turbulent mass transfer diffusivity Dtand the turbulent thermal diffusivity αtin the mass and heat conservation equations. By using the proposed model, the simulated results of CO2absorption by aqueous monoethanolamine (MEA) solution in an industrial scale column is presented, including MEA concentration, CO2loading and liquid phase temperature. The simulations are in agreement with the published experiment data.

Mathematical Modelling of Thermo-Hydro-Mechanical Behaviour for Concrete under Elevated Temperature

2014 ◽  
Vol 670-671 ◽  
pp. 355-364
Author(s):  
Shao Bo Zhang ◽  
Xiao Chun Wang ◽  
Xin Pu Shen
Keyword(s):  
Elevated Temperature ◽  
Stokes Equations ◽  
Constitutive Relations ◽  
Gaseous Mixture ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Energy Conservation Equation

A hydro-thermo-mechanical model was presented for concrete at elevated temperature. Three phases of continuum were adopted in this model: gaseous mixture of water vapor and dry air, liquid water, and solid skeleton of concrete. Mass conservation equations, linear momentum conservation equation, and energy conservation equation were derived on the basis of the macroscopic Navier-Stokes equations for a general continuum, along with assumptions made for the purpose of simplification. Mathematical relationships between selected primary variables and secondary variables were given with existing data from references. Specifications of the constitutive relations were made for the kinetic variables and their conjugate forces.

scholarly journals High-Resolution, Rapid-Scan Dual-Doppler Retrievals of Vertical Velocity in a Simulated Supercell

2019 ◽  
Vol 36 (8) ◽  
pp. 1477-1500 ◽  
Author(s):  
Nathan A. Dahl ◽  
Alan Shapiro ◽  
Corey K. Potvin ◽  
Adam Theisen ◽  
Joshua G. Gebauer ◽  
...  
Keyword(s):  
Variational Method ◽  
Vertical Velocity ◽  
Traditional Method ◽  
Mass Conservation ◽  
Conservation Equation ◽  
Observation System ◽  
Near Surface ◽  
Rapid Scan ◽  
Close Range ◽  
The Impact

AbstractObservation system simulation experiments are used to evaluate different dual-Doppler analysis (DDA) methods for retrieving vertical velocity w at grid spacings on the order of 100 m within a simulated tornadic supercell. Variational approaches with and without a vertical vorticity equation constraint are tested, along with a typical (traditional) method involving vertical integration of the mass conservation equation. The analyses employ emulated radar data from dual-Doppler placements 15, 30, and 45 km east of the mesocyclone, with volume scan intervals ranging from 10 to 150 s. The effect of near-surface data loss is examined by denying observations below 1 km in some of the analyses. At the longer radar ranges and when no data denial is imposed, the “traditional” method produces results similar to those of the variational method and is much less expensive to implement. However, at close range and/or with data denial, the variational method is much more accurate, confirming results from previous studies. The vorticity constraint shows the potential to improve the variational analysis substantially, reducing errors in the w retrieval by up to 30% for rapid-scan observations (≤30 s) at close range when the local vorticity tendency is estimated using spatially variable advection correction. However, the vorticity constraint also degrades the analysis for longer scan intervals, and the impact diminishes with increased range. Furthermore, analyses using 30-s data also frequently outperform analyses using 10-s data, suggesting a limit to the benefit of increasing the radar scan rate for variational DDA employing the vorticity constraint.

Macroscopic Modeling of Pedestrian Flow Considering the Herd Behavior

2013 ◽  
Vol 444-445 ◽  
pp. 906-911
Author(s):  
Yan Qun Jiang
Keyword(s):  
Numerical Experiments ◽  
Mass Conservation ◽  
Conservation Equation ◽  
Behavioral Characteristics ◽  
Herd Behavior ◽  
Pedestrian Flow ◽  
Evacuation Time ◽  
Macroscopic Modeling ◽  
Pedestrian Simulation ◽  
Mass Conservation Equation

This paper aims to mimic the herd behavior of pedestrian flow, i.e., the tendency towards majority when a congestion occurs, by macroscopic modeling approach. The macroscopic pedestrian simulation model is composed of a mass-conservation equation and a simple model to reflect behavioral characteristics of pedestrians based on a specific traffic situation. Numerical experiments are designed to show some preliminary results, e.g. the beneficial effect of herding on evacuation time in some situations.

On the effectiveness of shelter-in-place as a measure to reduce harm from atmospheric releases

2014 ◽  
Vol 12 (3) ◽  
pp. 245
Author(s):  
Shuming Du, PhD
Keyword(s):  
Exchange Rate ◽  
Mass Conservation ◽  
Conservation Equation ◽  
Hazardous Material ◽  
Air Exchange Rate ◽  
Chemical Attack ◽  
Chemical Accident ◽  
Atmospheric Releases ◽  
Toxic Load ◽  
Mass Conservation Equation

Shelter-in-place (SIP) is recommended by numerous entities as a measure to reduce harm in the event of a chemical accident or chemical attack taking place in the atmosphere. This article, based on solving mass conservation equation for indoor hazardous material, examines how effective SIP is to reduce the harm. It is shown that SIP can be effective when the shelter's air exchange rate is low and when the release duration is short. The effectiveness is strongly affected by the hazardous material itself: SIP is more effective for hazardous material with higher toxic load exponent. Another finding is that leaving the shelter promptly after the event can also be critical.

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