scholarly journals From laboratory experiments to geophysical tsunamis generated by subaerial landslides

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Manon Robbe-Saule ◽  
Cyprien Morize ◽  
Yann Bertho ◽  
Alban Sauret ◽  
Anthony Hildenbrand ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Risk Assessments ◽  
Small Scale ◽  
Maximal Amplitude ◽  
Tsunami Waves ◽  
Near Shore ◽  
Hazard And Risk ◽  
Gravity Driven ◽  
Granular Column ◽  
Good Agreement

AbstractModeling of tsunami waves generated by subaerial landslides is important to provide accurate hazard and risk assessments in coastal areas. We perform small-scale laboratory experiments where a tsunami-like wave is generated by the gravity-driven collapse of a subaerial granular column into water. We show that the maximal amplitude reached near-shore by the generated wave in our experiments is linked to the instantaneous immersed volume of grains and to the ultimate immersed deposit. Despite the differences in scale and geometry between our small-scale experiments and the larger-scale geophysical events, a rather good agreement is found between the experimental law and the field data. This approach offers an easy way to estimate the amplitude of paleo-tsunamis.

scholarly journals Rotating gravity currents: small-scale and large-scale laboratory experiments and a geostrophic model

2007 ◽  
Vol 578 ◽  
pp. 35-65 ◽  
Author(s):  
P. J. THOMAS ◽  
P. F. LINDEN
Keyword(s):  
Fresh Water ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Salt Water ◽  
Discharge Rate ◽  
Small Scale ◽  
Data Sets ◽  
Continuous Release ◽  
Dimensional Parameters ◽  
Gravity Driven

Laboratory experiments simulating gravity-driven coastal surface currents produced by estuarine fresh-water discharges into the ocean are discussed. The currents are generated inside a rotating tank filled with salt water by the continuous release of buoyant fresh water from a small source at the fluid surface. The height, the width and the length of the currents are studied as a function of the background rotation rate, the volumetric discharge rate and the density difference at the source. Two complementary experimental data sets are discussed and compared with each other. One set of experiments was carried out in a tank of diameter 1 m on a small-scale rotating turntable. The second set of experiments was conducted at the large-scale Coriolis Facility (LEGI, Grenoble) which has a tank of diameter 13 m. A simple geostrophic model predicting the current height, width and propagation velocity is developed. The experiments and the model are compared with each other in terms of a set of non-dimensional parameters identified in the theoretical analysis of the problem. These parameters enable the corresponding data of the large-scale and the small-scale experiments to be collapsed onto a single line. Good agreement between the model and the experiments is found.

The Halo Effect in Business Risk Audits: Can Strategic Risk Assessment Bias Auditor Judgment about Accounting Details?

2005 ◽  
Vol 80 (3) ◽  
pp. 921-939 ◽  
Author(s):  
Ed O'Donnell ◽  
Joseph J. Schultz
Keyword(s):  
Risk Assessment ◽  
Performance Evaluation ◽  
Laboratory Experiments ◽  
Halo Effect ◽  
Risk Assessments ◽  
Business Risk ◽  
Auditor Judgment ◽  
Strategic Risk ◽  
Strategic Assessment ◽  
Assessment Bias

Many auditors use an audit methodology that requires a strategic risk assessment of their client's business model as a first step for assessing audit risks. This study examines whether the holistic perspective that auditors acquire in making a strategic risk assessment influences the extent to which they adjust account-level risk assessments when they encounter changes in accounts that are inconsistent with information about client operations. Based on halo theory from the performance evaluation literature, we hypothesize that auditors who (1) perform (do not perform) strategic assessment, and (2) develop favorable (unfavorable) strategic risk assessments, are less (more) likely to adjust account-level risk assessments for inconsistent fluctuations. Data from two laboratory experiments using experienced auditors support both hypotheses. Findings suggest that the halo effect generated during strategic assessment influences judgment by altering auditor tolerance for inconsistent fluctuations.

scholarly journals Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Three Dimensional ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Small Clearance ◽  
Dimensional Simulation ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

Heat-flow experiments in liquid 4He with a variable cylindrical geometry

1987 ◽  
Vol 174 ◽  
pp. 209-231 ◽  
Author(s):  
H. Gao ◽  
G. Metcalfe ◽  
T. Jung ◽  
R. P. Behringer
Keyword(s):  
Cylindrical Geometry ◽  
Small Scale ◽  
Onset Of Convection ◽  
Aspect Ratios ◽  
A Value ◽  
Prandtl Numbers ◽  
Convection Rolls ◽  
Flow Experiments ◽  
Increasing Function ◽  
Good Agreement

This paper first describes an apparatus for measuring the Nusselt number N versus the Rayleigh number R of convecting normal liquid 4He layers. The most important feature of the apparatus is its ability to provide layers of different heights d, and hence different aspect ratios [Gcy ]. The horizontal cross-section of each layer is circular, and [Gcy ] is defined by [Gcy ] = D/2d where D is the diameter of the layer. We report results for 2.4 [les ] [Gcy ] [les ] 16 and for Prandtl numbers Pr spanning 0.5 [lsim ] Pr [lsim ] 0.9 These results are presented in terms of the slope N1 = RcdN/dR evaluated just above the onset of convection at Rc. We find that N1 is only a slowly increasing function of [Gcy ] in the range 6 [lsim ] [Gcy ] [lsim ] 16, and that it has a value there which is quite close to 0.72. This value of N1 is in good agreement with variational calcuations by Ahlers et al. (1981) pertinent to parallel convection rolls in cylindrical geometry. Particularly for [Gcy ] [lsim ] 6, we find additional small-scale structure in N1 associated with changes in the number of convection rolls with changing [Gcy ]. An additional test of the linearzied hydrodynamics is given by measurements of Rc. We find good agreement between theory and our data for Rc.

scholarly journals XV. On the electricity of rain and its origin in thunderstroms

1909 ◽  
Vol 209 (441-458) ◽  
pp. 379-413 ◽  
Keyword(s):  
Rainy Season ◽  
Laboratory Experiments ◽  
Small Scale ◽  
Electrical Discharges ◽  
The Government ◽  
Satisfactory Manner

Since Franklin first showed that thunder and lightning are caused by electrical discharges, there have been numerous theories to account for the production of electricity in thunderstorms, but none has been generally accepted by meteorologists. When attacking the problems of thunderstorm electricity, two methods naturally present themselves: we may either investigate the actual phenomena in the atmosphere, or try to repeat on a small scale in the laboratory the processes which may be supposed to take place during thunderstorms. During 1907-8 an investigation was undertaken on both these lines at the Meteorological Office of the Government of India in Simla. A systematic record was obtained by automatic instruments of the electricity brought down by the rain during practically the whole of one rainy season, and laboratory experiments were made to find the origin of the electricity of thunderstorms. The work has resulted in the formation of a new theory, which appears to account in a satisfactory manner for the electrical effects observed during thunderstorms. The following paper is divided into three parts:—Part I deals with the measurements of the electricity of the rain, Part II with the laboratory experiments, and Part III contains the new theory based on the results detailed in the previous parts.

What is the Smallest Earthquake Magnitude that Needs to be Considered in Assessing Liquefaction Hazard?

2019 ◽  
Vol 35 (3) ◽  
pp. 1441-1464 ◽  
Author(s):  
Russell A. Green ◽  
Julian J. Bommer
Keyword(s):  
Earthquake Magnitude ◽  
Risk Assessments ◽  
Soil Profiles ◽  
Building Structures ◽  
Liquefaction Hazard ◽  
Soil Deposits ◽  
Earthquake Size ◽  
Hazard And Risk ◽  
Hazard Assessments ◽  
Potential Impact

Probabilistic assessments of the potential impact of earthquakes on infrastructure entails the consideration of smaller magnitude events than those generally considered in deterministic hazard and risk assessments. In this context, it is useful to establish if there is a magnitude threshold below which the possibility of triggering liquefaction can be discounted because such a lower bound is required for probabilistic liquefaction hazard analyses. Based on field observations and a simple parametric study, we conclude that earthquakes as small as moment magnitude 4.5 can trigger liquefaction in extremely susceptible soil deposits. However, for soil profiles that are suitable for building structures, the minimum earthquake magnitude for the triggering of liquefaction is about 5. We therefore propose that in liquefaction hazard assessments of building sites, magnitude 5.0 be adopted as the minimum earthquake size considered, while magnitudes as low as 4.5 may be appropriate for some other types of infrastructure.

scholarly journals Laboratory Evaluation and Construction of Fully Recycled Low-Temperature Asphalt for Low-Volume Roads

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Christiane Raab ◽  
Manfred N. Partl
Keyword(s):  
Ambient Temperature ◽  
Laboratory Experiments ◽  
Traffic Simulation ◽  
Traffic Load ◽  
Laboratory Evaluation ◽  
Small Scale ◽  
Medium Scale ◽  
Low Volume Roads ◽  
Low Volume

Growing economy and increasing pollution evoke the need for more environmentally friendly road construction techniques and the saving of natural resources. In this context, cold recycling plays an important role since, on the one hand, it allows to reduce CO2 emissions drastically and, on the other hand, it offers a variety of opportunities for high percentages of recycling. Inspired by experience in Sweden, the international project “Optimal Recycling of Reclaimed Asphalts for low-traffic Pavement” (ORRAP) for low-volume roads in the Upper Rhine region aims to develop and establish a new strategy for 100% reclaimed asphalt pavement (RAP) at ambient temperature (20°C) without adding virgin bituminous binders or rejuvenators. The still ongoing research project involves laboratory experiments as well as in situ test sections. The link between small-scale laboratory experiments and in situ testing is provided by medium-scale traffic simulation in the laboratory. This paper describes results from medium-scale compaction in the laboratory using different methods as well as traffic simulation with a medium-scale mobile traffic load simulator. The results show that compaction in the laboratory at ambient temperature (20°) is very difficult to achieve. Nevertheless, it was found that compaction at a temperature of 60°C appears possible and provides promising results regarding stability and rutting enabling the in situ construction. The in situ pavement construction at ambient temperature on a low-volume road in Switzerland resulted in a visibly well-compacted and stable base course which was covered by a hot mix asphalt surface course the day after. The test section will be monitored closely over the next 12 months.

A scenario-based assessment of the tsunami hazard in Palermo, northern Sicily, and the southern Tyrrhenian Sea

2020 ◽  
Vol 500 (1) ◽  
pp. 63-80 ◽  
Author(s):  
Jack Dignan ◽  
Aaron Micallef ◽  
Christof Mueller ◽  
Attilio Sulli ◽  
Elisabetta Zizzo ◽  
...  
Keyword(s):  
Wave Height ◽  
Near Field ◽  
Mass Movement ◽  
Tsunami Hazard ◽  
Small Scale ◽  
Maximum Height ◽  
Northern Coast ◽  
Tyrrhenian Sea ◽  
Worst Case ◽  
Tsunami Waves

AbstractPalermo is a populous city situated on the northern coast of Sicily, bordered by the Tyrrhenian Sea. This central part of the Mediterranean Sea features dramatic bathymetry, numerous subaqueous landslides and is also the epicentre to many subaqueous earthquakes. As such, the region is an area prone to tsunamis. This investigation uses the Cornell Multi-Grid Coupled Tsunami (COMCOT) tsunami modelling package to simulate five near-field landslides, and five near-field earthquakes regarded as worst-case credible scenarios for Palermo. The seismic simulations produced waves on a very small scale, the largest being c. 5 cm at its maximum height, and none of the earthquake-generated tsunami waves produced any measurable inundation. The landslide simulations produced larger waves ranging from 1.9 to 12 m in maximum height, two of which resulted in inundation in areas surrounding the Port of Palermo. Sensitivity analysis identified that fault width and dislocation as well as landslide-specific gravity did have significant influence over maximum wave height, inundation and maximum run-up wave height. There are methodological issues limiting the extent to which this study forms a comprehensive tsunami hazard assessment of Palermo, such as gaps in bathymetric data, computational restrictions and lack of a probabilistic element. These issues are counteracted by the fact that this study does serve as a robust first step in identifying that landslides in the region may produce larger tsunami waves than earthquakes, and that the directionality of mass movement is critical in landslide-driven tsunami propagation in the southern Tyrrhenian region.

Sign in / Sign up

Export Citation Format

Share Document