scholarly journals A large-scale 2005–2012 flood map record derived from ENVISAT-ASAR data: United Kingdom as a test case

2021 ◽  
Vol 256 ◽  
pp. 112338
Author(s):  
Jie Zhao ◽  
Ramona Pelich ◽  
Renaud Hostache ◽  
Patrick Matgen ◽  
Wolfgang Wagner ◽  
...  
Keyword(s):  
United Kingdom ◽  
Large Scale ◽  
Test Case ◽  
Envisat Asar

Comparison of Various Discretization Schemes for Simulation of Large Field Case Reservoirs Using Unstructured Grids

2021 ◽  
Author(s):  
Samier Pierre ◽  
Raguenel Margaux ◽  
Darche Gilles
Keyword(s):  
Large Scale ◽  
Unstructured Grids ◽  
Computational Cost ◽  
Large Field ◽  
Real Field ◽  
Test Case ◽  
Generation Task ◽  
Field Case ◽  
Flux Approximation ◽  
Discretization Schemes

Abstract Solving the equations governing multiphase flow in geological formations involves the generation of a mesh that faithfully represents the structure of the porous medium. This challenging mesh generation task can be greatly simplified by the use of unstructured (tetrahedral) grids that conform to the complex geometric features present in the subsurface. However, running a million-cell simulation problem using an unstructured grid on a real, faulted field case remains a challenge for two main reasons. First, the workflow typically used to construct and run the simulation problems has been developed for structured grids and needs to be adapted to the unstructured case. Second, the use of unstructured grids that do not satisfy the K-orthogonality property may require advanced numerical schemes that preserve the accuracy of the results and reduce potential grid orientation effects. These two challenges are at the center of the present paper. We describe in detail the steps of our workflow to prepare and run a large-scale unstructured simulation of a real field case with faults. We perform the simulation using four different discretization schemes, including the cell-centered Two-Point and Multi-Point Flux Approximation (respectively, TPFA and MPFA) schemes, the cell- and vertex-centered Vertex Approximate Gradient (VAG) scheme, and the cell- and face-centered hybrid Mimetic Finite Difference (MFD) scheme. We compare the results in terms of accuracy, robustness, and computational cost to determine which scheme offers the best compromise for the test case considered here.

scholarly journals A Hydrologically Based Model for Delineating Hazard Zones in the Valleys of Debris Flow Basins

2016 ◽  
Author(s):  
Kaiheng Hu ◽  
Pu Li ◽  
Yong You ◽  
Fenghuan Su
Keyword(s):  
Debris Flow ◽  
Cross Sections ◽  
Large Scale ◽  
Test Case ◽  
Inundation Area ◽  
Hazard Zoning ◽  
Python Scripting ◽  
Minimal Data ◽  
Data Requirements ◽  
Debris Flow Hazard

Abstract. A hydrologically based model is developed for delineating hazard zones in valleys of debris flow basins. The basic assumption of this model is that the ratio of peak discharges of any two cross sections in a debris-flow basin is a power function of the ratio of their flow accumulation areas. Combining the advantages of the empirical and flow routing models of debris-flow hazard zoning, this hydrological model with minimal data requirements has the ability to produce hazard intensity values at different event magnitudes. The algorithms used in this model are designed in the framework of grid- based geographic processing and implemented completely on ArcGIS platform and a Python scripting environment. Qipan basin in the Wenchuan county of Sichuan province, southwest China where a large-scale debris-flow event occurred on July 11, 2013 was chosen as the test case for the model. The hazard zone identified by the model showed good agreement with the real inundation area of the event. The proposed method can help identify small hazard areas in upstream tributaries and the developed model is promising in terms of its application in debris-flow hazard zoning.

Predicting mesh density for adaptive modelling of the global atmosphere

2009 ◽  
Vol 367 (1907) ◽  
pp. 4523-4542 ◽  
Author(s):  
Hilary Weller
Keyword(s):  
Shallow Water ◽  
Shallow Water Equations ◽  
Large Scale ◽  
Mesh Adaptation ◽  
Similar Proportion ◽  
Test Case ◽  
Uniform Mesh ◽  
Coarse Mesh ◽  
Mesh Density ◽  
The Cost

The shallow water equations are solved using a mesh of polygons on the sphere, which adapts infrequently to the predicted future solution. Infrequent mesh adaptation reduces the cost of adaptation and load-balancing and will thus allow for more accurate mapping on adaptation. We simulate the growth of a barotropically unstable jet adapting the mesh every 12 h. Using an adaptation criterion based largely on the gradient of the vorticity leads to a mesh with around 20 per cent of the cells of a uniform mesh that gives equivalent results. This is a similar proportion to previous studies of the same test case with mesh adaptation every 1–20 min. The prediction of the mesh density involves solving the shallow water equations on a coarse mesh in advance of the locally refined mesh in order to estimate where features requiring higher resolution will grow, decay or move to. The adaptation criterion consists of two parts: that resolved on the coarse mesh, and that which is not resolved and so is passively advected on the coarse mesh. This combination leads to a balance between resolving features controlled by the large-scale dynamics and maintaining fine-scale features.

scholarly journals Fire safety case study of a railway tunnel: Smoke evacuation

2007 ◽  
Vol 11 (2) ◽  
pp. 207-222 ◽  
Author(s):  
Maele van ◽  
Bart Merci
Keyword(s):  
Fire Safety ◽  
Large Scale ◽  
Natural Ventilation ◽  
Real Life ◽  
Test Case ◽  
Fire Dynamics ◽  
Railway Tunnel ◽  
Tunnel Section ◽  
Safety Case ◽  
Smoke Evacuation

When a fire occurs in a tunnel, it is of great importance to assure the safety of the occupants of the tunnel. This is achieved by creating smoke-free spaces in the tunnel through control of the smoke gases. In this paper, results are presented of a study concerning the fire safety in a real scale railway tunnel test case. Numerical simulations are performed in order to examine the possibility of natural ventilation of smoke in inclined tunnels. Several aspects are taken into account: the length of the simulated tunnel section, the slope of the tunnel and the possible effects of external wind at one portal of the tunnel. The Fire Dynamics Simulator of the National Institute of Standards and Technology, USA, is applied to perform the simulations. The simulations show that for the local behavior of the smoke during the early stages of the fire, the slope of the tunnel is of little importance. Secondly, the results show that external wind and/or pressure conditions have a large effect on the smoke gases inside the tunnel. Finally, some idea for the value of the critical ventilation velocity is given. The study also shows that computational fluid dynamics calculations are a valuable tool for large scale, real life complex fire cases. .

scholarly journals Impacts of spatial resolution and representation of flow connectivity on large-scale simulation of floods

2017 ◽  
Author(s):  
Cherry May R. Mateo ◽  
Dai Yamazaki ◽  
Hyungjun Kim ◽  
Adisorn Champathong ◽  
Jai Vaze ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Large Scale ◽  
Flood Hazard ◽  
Regional Scale ◽  
Global Scale ◽  
Test Case ◽  
Efficiency Coefficient ◽  
Computational Power ◽  
Extreme Flood ◽  
Simulation Results

Abstract. Global-scale River Models (GRMs) are core tools for providing consistent estimates of global flood hazard, especially in data-scarce regions. Due to former limitations in computational power and input datasets, most GRMs have been developed to use simplified representation of flow physics and run at coarse spatial resolutions. With increasing computational power and improved datasets, the application of GRMs to finer resolutions is becoming a reality. To support development in this direction, the suitability of GRMs for application to finer resolutions needs to be assessed. This study investigates the impacts of spatial resolution and flow connectivity representation on the predictive capability of a GRM, CaMa-Flood, in simulating the 2011 extreme flood in Thailand. Analyses show that when single downstream connectivity (SDC) is assumed, simulation results deteriorate with finer spatial resolution; Nash–Sutcliffe Efficiency coefficient decreased by more than 35 % between simulation results at 10 km resolution and 1 km resolution. When multiple downstream connectivity (MDC) is represented, simulation results slightly improve with finer spatial resolution. The SDC simulations result in excessive backflows on very flat floodplains due to the restrictive flow directions in finer resolutions. MDC channels attenuated these effects by maintaining flow connectivity and flow capacity between floodplains in varying spatial resolutions. While a regional-scale flood was chosen as a test case, these findings are universal and can be extended to global-scale simulations. These results demonstrate that a GRM can be used for higher resolution simulations of large-scale floods, provided that MDC in rivers and floodplains is adequately represented in the model structure.

Discourse and Democracy

2020 ◽  
pp. 233-261
Author(s):  
Chris Heffer
Keyword(s):  
European Union ◽  
United Kingdom ◽  
Public Discourse ◽  
Large Scale ◽  
Weapons Of Mass Destruction ◽  
Democratic Legitimacy ◽  
Common Theme ◽  
The European Union ◽  
The United Kingdom ◽  
Voter Fraud

This chapter summarizes the main analytical moves in the TRUST heuristic for analyzing untruthfulness. It then applies the heuristic to three short texts that have been widely called out as lies: Trump’s tweet about large-scale voter fraud just before the 2016 presidential elections; the “Brexit Battle Bus” claim that the United Kingdom sent £350 million per week to the European Union; and Tony Blair’s 2002 statement to Parliament about Iraq possessing weapons of mass destruction. The cases share a common theme: the capacity of untruthful public discourse to undermine democratic legitimacy by, respectively, questioning the integrity of electoral procedures, harming the capacity of voters to make a rational choice, and undermining faith in the rational and responsible deliberation of one’s leaders. The chapter troubles the simple attribution of lying in these cases and shows how a TRUST analysis can lead to a deeper understanding of the types and ethical value of untruthfulness.

scholarly journals Ionized gas in the NGC 5253 supernebula: high spatial and spectral resolution observations with the JVLA and TEXES

2020 ◽  
Vol 497 (2) ◽  
pp. 1675-1683
Author(s):  
Sara C Beck ◽  
John Lacy ◽  
Jean Turner ◽  
Hauyu Baobab Liu ◽  
Thomas Greathouse ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Large Scale ◽  
Massive Star ◽  
Dwarf Galaxy ◽  
Data Cube ◽  
Test Case ◽  
Echelle Spectrograph ◽  
Full Data ◽  
Ionized Gas ◽  
Very Large Array

ABSTRACT The youngest, closest, and most compact embedded massive star cluster known excites the supernebula in the nearby dwarf galaxy NGC 5253. It is a crucial target and test case for studying the birth and evolution of the most massive star clusters. We present observations of the ionized gas in this source with high spatial and spectral resolution. The data include continuum images of free–free emission with ≈0.15 arcsec resolution made with the Karl G. Jansky Very Large Array (JVLA) at 15, 22, and 33 GHz, and a full data cube of the [S iv] 10.5 μm  fine-structure emission line with ≈4.5 km s−1 velocity resolution and 0.3 arcsec beam, obtained with the Texas Echelon Cross Echelle Spectrograph (TEXES) on Gemini North. We find that (1) the ionized gas extends out from the cluster in arms or jets, and (2) the ionized gas comprises two components offset both spatially and in velocity. We discuss mechanisms that may have created the observed velocity field; possibilities include large-scale jets or a subcluster falling on to the main source.

scholarly journals Feasibility of Measuring Sedentary Time Using Data From a Thigh-Worn Accelerometer

2020 ◽  
Vol 189 (9) ◽  
pp. 963-971 ◽  
Author(s):  
Mark Hamer ◽  
Emmanuel Stamatakis ◽  
Sebastien Chastin ◽  
Natalie Pearson ◽  
Matt Brown ◽  
...  
Keyword(s):  
United Kingdom ◽  
Sedentary Behavior ◽  
Large Scale ◽  
Sitting Time ◽  
Viewing Time ◽  
Men And Women ◽  
Self Reports ◽  
British Cohort Study ◽  
Male Sex ◽  
Using Data

Abstract In large-scale cohort studies, sedentary behavior has been routinely measured using self-reports or devices that apply a count-based threshold. We employed a gold standard postural allocation technique using thigh inclination and acceleration to capture free-living sedentary behavior. Participants aged 46.8 (standard deviation (SD), 0.7) years (n = 5,346) from the 1970 British Cohort Study (United Kingdom) were fitted with a waterproofed thigh-mounted accelerometer device (activPAL3 micro; PAL Technologies Ltd., Glasgow, United Kingdom) worn continuously over 7 days; data were collected in 2016–2018. Usable data were retrieved from 83.0% of the devices fitted, with 79.6% of the sample recording at least 6 full days of wear (at least 10 waking hours). Total daily sitting time (average times were 9.5 (SD, 2.0) hours/day for men and 9.0 (SD, 2.0) hours/day for women) accounted for 59.4% and 57.3% of waking hours in men and women, respectively; 73.8% of sample participants recorded ≥8 hours/day of sitting. Sitting in prolonged bouts of 60 continuous minutes or more accounted for 25.3% and 24.4% of total daily sitting in men and women, respectively. In mutually adjusted models, male sex, underweight, obesity, education, poor self-rated health, television-viewing time, and having a sedentary occupation were associated with higher device-measured sitting times. Thigh-worn accelerometry was feasibly deployed and should be considered for larger-scale national surveys.

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