scholarly journals NUMERICAL SIMULATION AND EXPERIMENTAL VALIDATION OF WAVE PATTERN INDUCED COORDINATE ERRORS IN AIRBORNE LIDAR BATHYMETRY

2018 ◽  
Vol XLII-2 ◽  
pp. 961-967 ◽  
Author(s):  
K. Richter ◽  
D. Mader ◽  
P. Westfeld ◽  
H.-G. Maas
Keyword(s):  
Numerical Simulation ◽  
Water Surface ◽  
Laser Scanning ◽  
Experimental Validation ◽  
Wave Pattern ◽  
Airborne Lidar ◽  
Simulation Tool ◽  
Water Interface ◽  
Air Water Interface ◽  
Airborne Lidar Bathymetry

Airborne LiDAR bathymetry (ALB) requires a refraction correction on the basis of Snell’s law at the air-water interface and a speedof- light correction to be applied on the raw laser data in order to achieve a geometric accurate representation of the water bottom. Strictly speaking, this requires exact knowledge about the local water surface inclination. If this information is not available, certain simplifications have to be introduced in correction methods. Common correction methods assume either a horizontal or a locally tilted planar water surface as well as an infinitesimally small thin laser ray, thus neglecting effects caused by the finite laser pulse diameter penetrating a curved surface. In our simulation approach, the refraction of finite diameter laser pulses passing the air/water interface is modeled differentially in a strict manner. The simulation tool is able to predict wave induced coordinate errors which have to be expected due to the neglections made in common refraction correction methods. Moreover, wave pattern dependent correction terms were be derived from systematic portions of the errors revealed by the simulations. The goal of this paper is to experimentally validate the coordinate errors predicted by the simulation tool. For that purpose, airborne laser bathymetry data of a 12 by 50 meter open air wave pool were processed, and the results were compared to reference data of the empty pool acquired by terrestrial laser scanning. The comparison showed that the effects predicted in the numerical simulation are confirmed by the experimental validation.

Blast Wave Mitigation from the Straight Tube by Using Water Part II - Numerical Simulation

2018 ◽  
Vol 910 ◽  
pp. 78-83 ◽  
Author(s):  
Yuta Sugiyama ◽  
Tomotaka Homae ◽  
Kunihiko Wakabayashi ◽  
Tomoharu Matsumura ◽  
Yoshio Nakayama
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Energy Transfer ◽  
Numerical Simulations ◽  
Blast Wave ◽  
Blast Waves ◽  
Straight Tube ◽  
Water Interface ◽  
Effect Of Water ◽  
Air Water Interface

This paper investigates explosions in a straight square tube in order to understand the mitigation effect of water on blast waves that emerge outside. Numerical simulations are used to assess the effect of water that is put inside the tube. The water reduces the peak overpressure outside, which agrees well with the experimental data. The increases in the kinetic and internal energies of the water are estimated, and the internal energy transfer at the air/water interface is shown to be an important factor in mitigating the blast wave in the present numerical method.

Dispersion of Particles on Liquid Surfaces

2011 ◽  
Author(s):  
Shriram B. Pillapakkam ◽  
Pushpendra Singh
Keyword(s):  
Numerical Simulation ◽  
Particle Size ◽  
Vertical Motion ◽  
Liquid Interface ◽  
Water Interface ◽  
Small Particles ◽  
Air Water Interface ◽  
Large Velocity ◽  
Simulation Results ◽  
Air Liquid Interface

In a recent study we have shown that when small particles, e.g., flour, pollen, glass, etc., contact an air-liquid interface, they disperse rapidly as if they were in an explosion. The rapid dispersion is due to the fact that the capillary force pulls particles into the interface causing them to accelerate to a large velocity. The vertical motion of a particle during its adsorption causes a radially-outward lateral (secondary) flow on the interface that causes nearby particles to move away. We present direct numerical simulation results for the adsorption of particles and show that the inertia of a particle plays an important role in its motion in the direction normal to a fluid-liquid interface. Although the importance of inertia diminishes with decreasing particle size, on an air-water interface the inertia continues to be important even when the size is as small as a few nanometers.

Unified Molecular View of the Air/Water Interface Based on Experimental and Theoretical χ(2)Spectra of an Isotopically Diluted Water Surface

2011 ◽  
Vol 133 (42) ◽  
pp. 16875-16880 ◽  
Author(s):  
Satoshi Nihonyanagi ◽  
Tatsuya Ishiyama ◽  
Touk-kwan Lee ◽  
Shoichi Yamaguchi ◽  
Mischa Bonn ◽  
...  
Keyword(s):  
Water Surface ◽  
Water Interface ◽  
Air Water Interface

Calcite lilypads and ledges at Lorusio Hot Springs, Kenya Rift Valley: travertine precipitation at the air-water interface

1999 ◽  
Vol 36 (4) ◽  
pp. 649-666 ◽  
Author(s):  
Robin W Renaut ◽  
Brian Jones ◽  
Caroline Le Turdu
Keyword(s):  
Water Surface ◽  
Microbial Mats ◽  
Hot Springs ◽  
Water Interface ◽  
Kenya Rift ◽  
Similar Morphology ◽  
Northern Kenya ◽  
Air Water Interface ◽  
Capillary Evaporation ◽  
Outflow Channel

Travertine forming at Lorusio Hot Springs in the northern Kenya Rift is constructed mainly by lilypads and ledges. The lilypads are flat, accretionary structures rooted to the substrate that are composed mostly of platy calcite crystals. They grow outward from a nucleus, subparallel to the water surface, at or just below the air-water interface. Precipitation results from rapid degassing of CO2. Ledges, which have a similar morphology and internal structure, are attached to the margin of a spring pool or outflow channel. As they grow laterally, lilypads and ledges may coalesce with their neighbours to produce thin (1-3 cm) beds of travertine, examples of which are exposed in subfossil deposits at the site. Once established, lilypads and ledges modify the outflow and can act as substrates for precipitation of other minerals and colonization by microbes on their cooler subaerial surfaces. Pore fluids are drawn upward through the lilypads by capillary evaporation. Amorphous silica then precipitates as surficial crusts upon microbial mats or forms spicular microstromatolites, some of which also contain calcite laminae. Efflorescent Na-CO3 salts commonly encrust the drier central platforms of the exposed lilypad. The unusual abundance of lilypads and ledges at Lorusio reflects (i) the low-relief setting and the hydrostatic head, which limit terrace development, and (ii) the high temperature (>75°C) of the waters, which inhibits colonization by microbial mats at crystal growth sites. Similar structures form in cave pools, evaporating brines, and freezing water at sites where precipitation is induced by several processes active at the air-water interface.

scholarly journals Experimental Validation of RELAP5 and TRACE5 for Licensing Studies of the Boron Injection System of Atucha II

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Alejandro I. Lazarte ◽  
William Fullmer ◽  
Martín Bertodano
Keyword(s):  
Heat Transfer ◽  
Nuclear Power ◽  
Experimental Validation ◽  
Injection System ◽  
Water Interface ◽  
Experimental Facility ◽  
Pressure Losses ◽  
Air Water Interface ◽  
Loss Of Coolant ◽  
Tank Level

This paper presents an experimental validation of RELAP5 and TRACE5 for licensing studies of the Atucha II-PHWR nuclear power plant. A scaled experimental facility, representing the boron injection system of Atucha II, was built. The system has a fundamental importance for loss of coolant accidents (LOCA) and anticipated transients without scram (ATWS). The experiment consists of the discharge of a tank that represents the boron tank filled with air or a mixture of air-water onto a discharge tank that represents the moderator tank. Both tanks are connected by a pipe which includes a valve and an orifice plate to model the pressure losses due to the fittings in the real system. The pressure and water level measured in the tanks are compared with the RELAP5 and TRACE5 predictions. The codes predict the pressure in the tanks accurately. However, both codes overpredict the heat transfer in the boron tank air-water interface which produces a greater expansion of the air which leads to a small discrepancy in the boron tank level prediction.

scholarly journals ANALYSIS OF THE EFFECT OFWAVE PATTERNS ON REFRACTION IN AIRBORNE LIDAR BATHYMETRY

2016 ◽  
Vol XLI-B1 ◽  
pp. 133-139 ◽  
Author(s):  
P. Westfeld ◽  
K. Richter ◽  
H.-G. Maas ◽  
Robert Weiß
Keyword(s):  
Water Body ◽  
Wave Pattern ◽  
Airborne Lidar ◽  
Beam Divergence ◽  
Wave Patterns ◽  
Wave Effects ◽  
Local Wave ◽  
Airborne Lidar Bathymetry ◽  
Coordinate Correction ◽  
Random Part

This contribution investigates the effects of wave patterns on 3D point coordinate accuracy in LiDAR bathymetry. The finite diameter refracted laser pulse path passing the air/water interface is modelled differentially and in a strict manner. Typical wave patterns are simulated and their impact on the 3D coordinates at the bottom of the water body are analysed. It can be shown that the effects of waves within small LiDAR bathymetry footprints on the depth and planimetry coordinates is significant. Planimetric effects may reach several decimetres or even metres, and depth coordinate errors also reach several decimetres, even in case of horizontal water body bottom. The simplified assumption of averaging wave effects often made in many ALB applications is not only fulfilled in cases of a very large beam divergence under certain wave pattern conditions. Modern smaller beam divergence systems will mostly experience significant wave pattern dependent coordinate errors. The results presented here thus form a basis for a more strict coordinate correction if the wave pattern can be modelled from the LiDAR bathymetry water surface reflections or other observations. Moreover, it will be shown that the induced coordinate errors contain systematic parts in addition to the local wave surface dependent quasi-random part, which allows for the formulation of wave pattern type dependent correction terms.

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