scholarly journals Estimating Turbulence Distribution over a Heterogeneous Path Using Time-Lapse Imagery from Dual Cameras

2021 ◽  
Vol 11 (13) ◽  
pp. 6221
Author(s):  
Benjamin Wilson ◽  
Santasri Bose-Pillai ◽  
Jack McCrae ◽  
Kevin Keefer ◽  
Steven Fiorino
Keyword(s):  
Surface Layer ◽  
Short Range ◽  
Time Lapse ◽  
Single Camera ◽  
Light Emitting ◽  
Differential Motion ◽  
Horizontal Path ◽  
Sonic Anemometers ◽  
Altitude Dependence ◽  
Distant Target

Knowledge of turbulence distribution along an experimental path can help in effective turbulence compensation and mitigation. Although scintillometers are traditionally used to measure the strength of turbulence, they provide a path-integrated measurement and have limited operational ranges. A technique to profile turbulence using time-lapse imagery of a distant target from spatially separated cameras is presented here. The method uses the turbulence induced differential motion between pairs of point features on a target, sensed at a single camera and between cameras to extract turbulence distribution along the path. The method is successfully demonstrated on a 511 m almost horizontal path going over half concrete and half grass. An array of Light-Emitting Diodes (LEDs) of non-uniform separation is imaged by a pair of cameras, and the extracted turbulence profiles are validated against measurements from 3D sonic anemometers placed along the path. A short-range experiment with a heat source to create local turbulence spike gives good results as well. Because the method is phase-based, it does not suffer from saturation issues and can potentially be applied over long ranges. Although in the present work, a cooperative target has been used, the technique can be used with non-cooperative targets. Application of the technique to images collected over slant paths with elevated targets can aid in understanding the altitude dependence of turbulence in the surface layer.

Short-range visible light ranging and detecting system using illumination light emitting diodes

2016 ◽  
Vol 10 (3) ◽  
pp. 94-99 ◽  
Author(s):  
Dehao Wu ◽  
Chen Chen ◽  
Zabih Ghassemlooy ◽  
Wen-De Zhong
Keyword(s):  
Visible Light ◽  
Short Range ◽  
Light Emitting Diodes ◽  
Light Emitting

scholarly journals Influence of the Atmospheric Surface Layer on a Turbulent Flow Downstream of a Ship Superstructure

2013 ◽  
Vol 30 (8) ◽  
pp. 1803-1819 ◽  
Author(s):  
Luksa Luznik ◽  
Cody J. Brownell ◽  
Murray R. Snyder ◽  
Hyung Suk Kang
Keyword(s):  
Surface Layer ◽  
Atmospheric Surface Layer ◽  
The United States ◽  
Naval Academy ◽  
Mean Flow ◽  
Flow Distortion ◽  
Turbulent Statistics ◽  
Sonic Anemometers ◽  
Flight Deck ◽  
Inflow Conditions

Abstract This paper describes a set of turbulence measurements at sea in the area of high flow distortion in the near-wake and recirculation zone behind a ship's superstructure that is similar in geometry to a helicopter hangar/flight deck arrangement found on many modern U.S. Navy ships. The instrumented ship is a 32-m-long training vessel operated by the United States Naval Academy that has been modified by adding a representative flight deck and hangar structure. The flight deck is instrumented with up to seven sonic anemometers/thermometers that are used to obtain simultaneous velocity measurements at various spatial locations on the flight deck, and one sonic anemometer at bow mast is used to characterize inflow atmospheric boundary conditions. Data characterizing wind over the deck at an incoming angle of 0° (head winds) and wind speeds from 2 to 10 m s−1 obtained in the Chesapeake Bay are presented and discussed. Turbulent statistics of inflow conditions are analyzed using the Kaimal universal turbulence spectral model for the atmospheric surface layer and show that for the present dataset this approach eliminates the need to account for platform motion in computing variances and covariances. Conditional sampling of mean flow and turbulence statistics at the flight deck indicate no statistically significant variations between unstable, stable, and neutral atmospheric inflow conditions, and the results agree with the published data for flows over the backward-facing step geometries.

Evaluation of time lapse of the near-surface layer due to precipitation

2018 ◽  
Author(s):  
Junzo Kasahara ◽  
Yoko Hasada ◽  
Yasuhiro Sugimoto ◽  
Hirotaka Kawashima ◽  
Yasutomo Yamauchi ◽  
...  
Keyword(s):  
Surface Layer ◽  
Time Lapse ◽  
Near Surface

scholarly journals Monitoring the optical turbulence in the surface layer at Dome C, Antarctica, with sonic anemometers

2015 ◽  
Vol 454 (4) ◽  
pp. 4304-4315 ◽  
Author(s):  
E. Aristidi ◽  
J. Vernin ◽  
E. Fossat ◽  
F.-X. Schmider ◽  
T. Travouillon ◽  
...  
Keyword(s):  
Surface Layer ◽  
Optical Turbulence ◽  
Sonic Anemometers

scholarly journals Characterization of Turbulence in the Neutral and Stable Surface Layer at Jang Bogo Station, Antarctica

Atmosphere ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1095
Author(s):  
Mauro Mazzola ◽  
Angelo Pietro Viola ◽  
Taejin Choi ◽  
Francesco Tampieri
Keyword(s):  
Surface Layer ◽  
Large Fraction ◽  
Low Frequency ◽  
Systematic Investigation ◽  
Second Order ◽  
Time Interval ◽  
Stable Conditions ◽  
Stable Surface Layer ◽  
Sonic Anemometers ◽  
Submeso Motions

The availability of 5-year time series of velocity and temperature data from two sonic anemometers installed at Jang Bogo Station, Antarctica, allowed a systematic investigation of the turbulence features in a stable layer affected by submeso motions and characterized by the vertical divergence of some second-order moments for a large fraction of time (quite a non-ideal surface layer). The investigation of the effect of the averaging time interval on the statistics of the second-order moments showed that this is greater for the variances of the velocity components with respect to that for the vertical fluxes. This corresponds to a greater contribution from low-frequency motions. The turbulence statistics were investigated and compared with current literature results in terms of vertical structure, share of energy between horizontal and vertical components, skewness of the vertical velocity and turbulent velocities. As a general result, all the normalized second-order moments show a clear change passing from neutral to stable conditions, passing through the range of bulk Richardson number equal to 0.1–1.

Estimation of Fried's Coherence Diameter from Differential Motion of Features in Time-lapse Imagery

2019 ◽  
Author(s):  
Santasri R. Bose-Pillai ◽  
Jack E. McCrae ◽  
Michael A. Rucci ◽  
Eric M. Kwasniewski ◽  
Steven T. Fiorino
Keyword(s):  
Time Lapse ◽  
Differential Motion

A different type of amphibian mesoderm morphogenesis in Ceratophrys ornata

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 307-317 ◽  
Author(s):  
S.M. Purcell ◽  
R. Keller
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Surface Layer ◽  
Xenopus Laevis ◽  
Dorsal Surface ◽  
Time Lapse ◽  
Surface Epithelium ◽  
Histological Sections ◽  
Fourth Zone ◽  
Scanning Electron

Ceratophrys ornata, the Argentinean horned frog, has a significantly different pattern of early morphogenesis than does the most studied amphibian, Xenopus laevis. Time-lapse videomicroscopy, scanning electron microscopy, histological sections and lineage tracers have shown that, in C. ornata, some prospective notochord, somite and tailbud mesoderm cells leave the surface epithelium of the archenteron by ingression. After gastrulation, SEM reveals cells with constricted apices and a bottle shape in three zones on the archenteron roof and in a fourth zone around the blastopore. Prospective somitic tissue ingresses first from two lateral zones, followed by ingression of prospective notochord from the medial zone and tailbud mesoderm from the circumblastoporal zone. This is unlike X. laevis, in which no cells with constricted apices are present on the dorsal surface of the archenteron, nor do any cells ingress into the deep mesodermal layers from the surface layer.

scholarly journals The Effect of Filter Dimension on the Subgrid-Scale Stress, Heat Flux, and Tensor Alignments in the Atmospheric Surface Layer

2007 ◽  
Vol 24 (3) ◽  
pp. 360-375 ◽  
Author(s):  
Chad W. Higgins ◽  
Charles Meneveau ◽  
Marc B. Parlange
Keyword(s):  
Heat Flux ◽  
Surface Layer ◽  
Environmental Science ◽  
Field Experiments ◽  
Atmospheric Stability ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Subgrid Scale ◽  
Sonic Anemometers ◽  
Two Dimensional Filtering

Abstract In field experiments designed to study subgrid-scale parameterizations for large eddy simulation, the flow field is often measured and then filtered in two-dimensional planes. This two-dimensional filtering serves as a surrogate for three-dimensional filtering. The question of whether this will yield accurate results in subgrid-scale (SGS) models is addressed by analyzing data from a field experiment in which 16 sonic anemometers were deployed in a four by four grid. The experiment was held in July 2002 at the Surface Layer Turbulence and Environmental Science Test (SLTEST) facility in the Utah West Desert. The full SGS stress tensor and its parameterizations using both two- and three-dimensional filterings are obtained. Comparisons are given between two- and three-dimensional filterings of the field measurements based on probability density functions (PDFs) and energy spectra of the SGS stress elements. The PDFs reveal that quantities calculated with two-dimensional filtering exhibit greater intermittency than those computed with three-dimensional filtering at the same scale. From the spectra it is observed that the different filtering methods result in similar behavior, but that spectra of SGS stress components computed with a three-dimensional filter roll off at a slightly lower wavenumber than those computed with a two-dimensional filter. The PDFs and spectra of the stresses calculated with two- and three-dimensional filters can be made to collapse by reducing the three-dimensional filter scale according to Δ3−D = 0.84Δ2−D. Geometric alignment analyses are performed for the SGS heat flux, SGS stress, and filtered strain rate for the cases of stable, near-neutral, and unstable atmospheric stabilities. Under unstable and near-neutral atmospheric stability, two-dimensional filtering yields acceptable results; however, under stable atmospheric stability, a new approach is recommended and delineated.

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