scholarly journals Numerical Investigations on the Instability of Boulders Impacted by Experimental Coastal Flows

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1557
Author(s):  
Liang Wang ◽  
Lidia Bressan ◽  
Stefano Tinti
Keyword(s):  
Laboratory Data ◽  
High Energy ◽  
Coastal Sediments ◽  
Water Model ◽  
Incipient Motion ◽  
Shallow Water Model ◽  
Instability Condition ◽  
Wide Range ◽  
Drag And Lift ◽  
The University

Coastal boulders transported inland by marine hazards, such as tsunamis and storms, are commonly found worldwide. Studies on the transport process of coastal boulders contribute to the understanding of a wide range of phenomena such as high-energy flow events, fluid-structure interaction, and coastal sediments. Consequently, it is crucial to understand how boulders move, but even more important to determine the instability condition for boulder transport. The hydrodynamic formulas including drag and lift coefficients are widely used to predict the incipient motion of boulders while few studies are conducted to evaluate the capability of these formulas. Recently, a series of laboratory experiments carried out at the Hydraulic Engineering Laboratory (Italian acronym LIDR) of the University of Bologna, Italy, revealed that boulders can start moving when the flow height and flow velocity are lower than the theoretical threshold computed by hydraulic formulas. In this paper, we use a numerical shallow water model to reproduce these freely available laboratory data with the aim of testing the capability of the model in capturing the main evolution of the process, and of casting new light on the instability condition of coastal boulders.

scholarly journals A Shallow Water Model for Convective Self-Aggregation

2020 ◽  
Author(s):  
Da Yang
Keyword(s):  
Shallow Water ◽  
Gravity Waves ◽  
Large Scale ◽  
Wave Pattern ◽  
Water Model ◽  
Shallow Water Model ◽  
Modeling Framework ◽  
Convective Storms ◽  
Wide Range ◽  
Self Aggregation

AbstractRandomly distributed convective storms can self-aggregate in the absence of large-scale forcings. Here we present a 1D shallow water model to study the convective self-aggregation. This model simulates the dynamics of the planetary boundary layer and represents convection as a triggered process. Once triggered, convection lasts for finite time and occupies finite length. We show that the model can successfully simulate self-aggregation, and that the results are robust to a wide range of parameter values. In the simulations, convection excites gravity waves. The gravity waves then form a standing wave pattern, separating the domain into convectively active and inactive regions. We analyze the available potential energy (APE) budget and show that convection generates APE, providing energy for self-aggregation. By performing dimensional analysis, we develop a scaling theory for the size of convective aggregation, which is set by the gravity wave speed, damping timescale, and number density of convective storms. This paper provides a simple modeling framework to further study convective self-aggregation.

scholarly journals A Second-Order Well-Balanced Finite Volume Scheme for the Multilayer Shallow Water Model with Variable Density

Mathematics ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 848
Author(s):  
Ernesto Guerrero Fernández ◽  
Manuel Jesús Castro-Díaz ◽  
Tomás Morales de Luna
Keyword(s):  
Shallow Water ◽  
Finite Volume ◽  
Hyperbolic Equations ◽  
Laboratory Data ◽  
Variable Density ◽  
Second Order ◽  
Water Model ◽  
Finite Volume Scheme ◽  
Reconstruction Technique ◽  
Shallow Water Model

In this work, we consider a multilayer shallow water model with variable density. It consists of a system of hyperbolic equations with non-conservative products that takes into account the pressure variations due to density fluctuations in a stratified fluid. A second-order finite volume method that combines a hydrostatic reconstruction technique with a MUSCL second order reconstruction operator is developed. The scheme is well-balanced for the lake-at-rest steady state solutions. Additionally, hints on how to preserve a general class of stationary solutions corresponding to a stratified density profile are also provided. Some numerical results are presented, including validation with laboratory data that show the efficiency and accuracy of the approach introduced here. Finally, a comparison between two different parallelization strategies on GPU is presented.

Centrifugal, barotropic and baroclinic instabilities of isolated ageostrophic anticyclones in the two-layer rotating shallow water model and their nonlinear saturation

2014 ◽  
Vol 762 ◽  
pp. 5-34 ◽  
Author(s):  
Noé Lahaye ◽  
Vladimir Zeitlin
Keyword(s):  
Shallow Water ◽  
Initial Conditions ◽  
Vertical Shear ◽  
Water Model ◽  
Shallow Water Model ◽  
Nonlinear Saturation ◽  
Centrifugal Instability ◽  
Wide Range ◽  
Nonlinear Mechanism ◽  
Rotating Shallow Water

AbstractInstabilities of isolated anticyclonic vortices in the two-layer rotating shallow water model are studied at Rossby numbers up to two, with the main goal to understand the interplay between the classical centrifugal instability and other ageostrophic instabilities. We find that different types of instabilities with low azimuthal wavenumbers exist, and may compete. In a wide range of parameters, an asymmetric version of the standard centrifugal instability has larger growth rate than the latter. The dependence of the instabilities on the parameters of the flow, i.e. Rossby and Burger numbers, vertical shear and the ratios of the layers’ thicknesses and densities, is investigated. The zones of dominance of each instability are determined in the parameter space. Nonlinear saturation of these instabilities is then studied with the help of a high-resolution finite-volume numerical scheme, by using the unstable modes identified from the linear stability analysis as initial conditions. Differences in nonlinear development of the competing centrifugal and ageostrophic barotropic instabilities are evidenced. A nonlinear mechanism of axial symmetry breaking during the saturation of the centrifugal instability is displayed.

Microfabrication research at the National Submicron Facility

1983 ◽  
Vol 41 ◽  
pp. 86-89
Author(s):  
E.D. Wolf
Keyword(s):  
Integrated Circuits ◽  
Particle Physics ◽  
High Speed ◽  
New Technology ◽  
High Energy ◽  
High Energy Particle ◽  
New Science ◽  
Wide Range ◽  
Intermediate Domain ◽  
Circuit Function

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.

TEM study of boron additions to cobalt aluminide

1988 ◽  
Vol 46 ◽  
pp. 546-547
Author(s):  
Gerald B. Feldewerth
Keyword(s):  
High Temperature ◽  
Turbine Engines ◽  
Major Drawback ◽  
University Of Missouri ◽  
Specific Strength ◽  
Aerospace Applications ◽  
Wide Range ◽  
Ordered Alloys ◽  
The University ◽  
Very High

In recent years an increasing emphasis has been placed on the study of high temperature intermetallic compounds for possible aerospace applications. One group of interest is the B2 aiuminides. This group of intermetaliics has a very high melting temperature, good high temperature, and excellent specific strength. These qualities make it a candidate for applications such as turbine engines. The B2 aiuminides exist over a wide range of compositions and also have a large solubility for third element substitutional additions, which may allow alloying additions to overcome their major drawback, their brittle nature.One B2 aluminide currently being studied is cobalt aluminide. Optical microscopy of CoAl alloys produced at the University of Missouri-Rolla showed a dramatic decrease in the grain size which affects the yield strength and flow stress of long range ordered alloys, and a change in the grain shape with the addition of 0.5 % boron.

Compact back-scattered electrons' energy analyzer for standard SEM

1994 ◽  
Vol 52 ◽  
pp. 488-489
Author(s):  
S. Likharev ◽  
A. Kramarenko ◽  
V. Vybornov
Keyword(s):  
Depth Resolution ◽  
High Energy ◽  
Primary Beam ◽  
Layer By Layer ◽  
Energy Analyzer ◽  
High Energy Part ◽  
Small Window ◽  
Energy Part ◽  
Wide Range ◽  
High Voltage Supply

At present time the interest is growing considerably for theoretical and experimental analysis of back-scattered electrons (BSE) energy spectra. It was discovered that a special angle and energy nitration of BSE flow could be used for increasing a spatial resolution of BSE mode, sample topography investigations and for layer-by layer visualizing of a depth structure. In the last case it was shown theoretically that in order to obtain suitable depth resolution it is necessary to select a part of BSE flow with the directions of velocities close to inverse to the primary beam and energies within a small window in the high-energy part of the whole spectrum.A wide range of such devices has been developed earlier, but all of them have considerable demerit: they can hardly be used with a standard SEM due to the necessity of sufficient SEM modifications like installation of large accessories in or out SEM chamber, mounting of specialized detector systems, input wires for high voltage supply, screening a primary beam from additional electromagnetic field, etc. In this report we present a new scheme of a compact BSE energy analyzer that is free of imperfections mentioned above.

Sharing of Worldwide Spread Knowledge Using Hypermedia Facilities & Fast Communication Protocols (Mosaic and World Wide Web): The Example of ExPASy

1995 ◽  
Vol 34 (01/02) ◽  
pp. 75-78 ◽  
Author(s):  
R. D. Appel ◽  
O. Golaz ◽  
Ch. Pasquali ◽  
J.-C. Sanchez ◽  
A. Bairoch ◽  
...  
Keyword(s):  
World Wide Web ◽  
World Wide ◽  
Relevant Literature ◽  
Communication Protocols ◽  
Laboratory Data ◽  
Central Element ◽  
University Hospital ◽  
New Information ◽  
The University ◽  
Link Information

Abstract:The sharing of knowledge worldwide using hypermedia facilities and fast communication protocols (i.e., Mosaic and World Wide Web) provides a growth capacity with tremendous versatility and efficacy. The example of ExPASy, a molecular biology server developed at the University Hospital of Geneva, is striking. ExPASy provides hypermedia facilities to browse through several up-to-date biological and medical databases around the world and to link information from protein maps to genome information and diseases. Its extensive access is open through World Wide Web. Its concept could be extended to patient data including texts, laboratory data, relevant literature findings, sounds, images and movies. A new hypermedia culture is spreading very rapidly where the international fast transmission of documents is the central element. It is part of the emerging new “information society”.

Biodiversity in Vegetation and Ecosystems»: symposium on the occasion of the retirement of Prof. Dr. Fred J.A. Daniels (Munster, Germany, July 11, 2008)

2008 ◽  
pp. 123-124
Author(s):  
N. V. Matveyeva
Keyword(s):  
Wide Range ◽  
65Th Anniversary ◽  
The University

July 2008 in Münster (Germany) hosted a Symposium on the occasion of the 65th anniversary of Professor of the University of this city, Fred Daniels (Frederikus Josephus Alphonsus Daniëls). The title of this Symposium «Biodiversity in Vegetation and Ecosystems» reflected the wide range of interests of the celebrant.

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