Review of the manuscript entitled “Characterization of flow recirculation zones in complex terrain using multi-lidar measurements”

2018 ◽  
Author(s):  
Anonymous
Keyword(s):  
Complex Terrain ◽  
Flow Recirculation ◽  
Lidar Measurements ◽  
Recirculation Zones

scholarly journals Characterization of flow recirculation zones at the Perdigão site using multi-lidar measurements

2019 ◽  
Vol 19 (4) ◽  
pp. 2713-2723 ◽  
Author(s):  
Robert Menke ◽  
Nikola Vasiljević ◽  
Jakob Mann ◽  
Julie K. Lundquist
Keyword(s):  
Reverse Flow ◽  
Atmospheric Stability ◽  
Resource Assessment ◽  
Atmospheric Conditions ◽  
Recirculation Flow ◽  
Flow Recirculation ◽  
Wind Speeds ◽  
Lidar Measurements ◽  
Recirculation Zones ◽  
Wind Resource

Abstract. Because flow recirculation can generate significant amounts of turbulence, it can impact the success of wind energy projects. This study uses unique Doppler lidar observations to quantify occurrences of flow recirculation on lee sides of ridges. An extensive dataset of observations of flow over complex terrain is available from the Perdigão 2017 field campaign over a period of 3 months. The campaign site was selected because of the unique terrain feature of two nearly parallel ridges with a valley-to-ridge-top height difference of about 200 m and a ridge-to-ridge distance of 1.4 km. Six scanning Doppler lidars probed the flow field in several vertical planes orthogonal to the ridges using range–height indicator scans. With this lidar setup, we achieved vertical scans of the recirculation zone at three positions along two parallel ridges. We construct a method to identify flow recirculation zones in the scans, as well as define characteristics of these zones. According to our data analysis, flow recirculation, with reverse flow wind speeds greater than 0.5 m s−1, occurs over 50 % of the time when the wind direction is perpendicular to the direction of the ridges. Atmospheric conditions, such as atmospheric stability and wind speed, affect the occurrence of flow recirculation. Flow recirculation occurs more frequently during periods with wind speeds above 8 m s−1. Recirculation within the valley affects the mean wind and turbulence fields at turbine heights on the downwind ridge in magnitudes significant for wind resource assessment.

scholarly journals Characterization of flow recirculation zones in complex terrain using multi-lidar measurements

2018 ◽  
Author(s):  
Robert Menke ◽  
Nikola Vasiljević ◽  
Jakob Mann ◽  
Julie K. Lundquist
Keyword(s):  
Complex Terrain ◽  
Reverse Flow ◽  
Atmospheric Stability ◽  
Resource Assessment ◽  
Atmospheric Conditions ◽  
Recirculation Flow ◽  
Flow Recirculation ◽  
Wind Speeds ◽  
Recirculation Zones ◽  
Wind Resource

Abstract. Because flow recirculation can generate significant amounts of turbulence, it can impact the success of wind energy projects. This study uses unique Doppler lidar observations to quantify occurrences of flow recirculation on lee sides of ridges. An extensive dataset of observations of flow over complex terrain is available from the Perdigão-2017 field campaign over a period of three months. The campaign site was selected because of the unique terrain feature of two nearly parallel ridges with a valley-to-ridge-top height difference of about 200 m and a ridge-to-ridge distance of 1.4 km. Six scanning Doppler lidars probed the flow field in several vertical planes orthogonal to the ridges using range-height-indicator scans. With this lidar setup, we achieved vertical scans of the recirculation zone at three positions along two parallel ridges. We construct a method to identify flow recirculation zones in the scans, as well as define characteristics of these zones. According to our data analysis, flow recirculation, with reverse flow wind speeds greater than 0.5 m s−1, occurs over 50 % of the time when the wind direction is perpendicular to the direction of the ridges. Atmospheric conditions, such as atmospheric stability and wind speed, affect the occurrence of flow recirculation. Flow recirculation occurs more frequently during periods with wind speeds above 8 m s−1. Recirculation within the valley affects the mean wind and turbulence fields at turbine heights on the downwind ridge in magnitudes significant for wind resource assessment.

Flow recirculation zone length and shear rate are differentially affected by stenosis severity in human coronary arteries

2013 ◽  
Vol 304 (4) ◽  
pp. H559-H566 ◽  
Author(s):  
Ashkan Javadzadegan ◽  
Andy S. C. Yong ◽  
Michael Chang ◽  
Austin C. C. Ng ◽  
John Yiannikas ◽  
...  
Keyword(s):  
Shear Rate ◽  
Coronary Arteries ◽  
Recirculation Zone ◽  
Fluid Dynamic ◽  
Zone Length ◽  
Flow Recirculation ◽  
Stenosis Severity ◽  
Recirculation Zones ◽  
The Relationship

Flow recirculation zones and shear rate are associated with distinct pathogenic biological pathways relevant to thrombosis and atherogenesis. The interaction between stenosis severity and lesion eccentricity in determining the length of flow recirculation zones and peak shear rate in human coronary arteries in vivo is unclear. Computational fluid dynamic simulations were performed under resting and hyperemic conditions on computer-generated models and three-dimensional (3-D) reconstructions of coronary arteriograms of 25 patients. Boundary conditions for 3-D reconstructions simulations were obtained by direct measurements using a pressure-temperature sensor guidewire. In the computer-generated models, stenosis severity and lesion eccentricity were strongly associated with recirculation zone length and maximum shear rate. In the 3-D reconstructions, eccentricity increased recirculation zone length and shear rate when lesions of the same stenosis severity were compared. However, across the whole population of coronary lesions, eccentricity did not correlate with recirculation zone length or shear rate ( P = not signficant for both), whereas stenosis severity correlated strongly with both parameters ( r = 0.97, P < 0.001, and r = 0.96, P < 0.001, respectively). Nonlinear regression analyses demonstrated that the relationship between stenosis severity and peak shear was exponential, whereas the relationship between stenosis severity and recirculation zone length was sigmoidal, with an apparent threshold effect, demonstrating a steep increase in recirculation zone length between 40% and 60% diameter stenosis. Increasing stenosis severity and lesion eccentricity can both increase flow recirculation and shear rate in human coronary arteries. Flow recirculation is much more sensitive to mild changes in the severity of intermediate stenoses than is peak shear.

scholarly journals Study of the effect of different type of aerosols on UV-B radiation from measurements during EARLINET

2003 ◽  
Vol 3 (5) ◽  
pp. 4671-4700
Author(s):  
D. S. Balis ◽  
V. Amiridis ◽  
C. Zerefos ◽  
A. Kazantzidis ◽  
S. Kazadzis ◽  
...  
Keyword(s):  
Total Ozone ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Combined Use ◽  
Lidar Measurements ◽  
The Vertical Distribution ◽  
Aerosol Type

Abstract. Routine lidar measurements of the vertical distribution of the aerosol extinction coefficient and the extinction-to-backscatter ratio have been performed at Thessaloniki, Greece using a Raman lidar system in the frame of the EARLINET project since 2000. Spectral and broadband UV-B irradiance measurements, as well as total ozone observations, were available whenever lidar measurements were obtained. From the available measurements several cases could be identified that allowed the study of the effect of different types of aerosol on the levels of the UV-B solar irradiance at the Earth's surface. The TUV radiative transfer model has been used to simulate the irradiance measurements, using total ozone and the lidar aerosol data as input. From the comparison of the model results with the measured spectra the effective single scattering albedo was determined using an iterative procedure, which has been verified against results from the 1998 Lindenberg Aerosol Characterization Experiment. It is shown that the same aerosol optical depth and same total ozone values can show differences up to 10% in the UV-B irradiance at the Earth's surface, which can be attributed to differences in the aerosol type. It is shown that the combined use of the estimated single scattering albedo and the measured extinction-to-backscatter ratio leads to a better characterization of the aerosol type probed.

Detailed experimental and numerical characterization of turbulent flow in components of a water treatment plant

2019 ◽  
Vol 80 (11) ◽  
pp. 2117-2130
Author(s):  
Ivan Matías Ragessi ◽  
Carlos Marcelo García ◽  
Santiago Márquez Damián ◽  
Cecilia Pozzi Piacenza ◽  
Mariano Ignacio Cantero
Keyword(s):  
Water Treatment ◽  
Turbulent Flow ◽  
Treatment Plant ◽  
Acoustic Doppler Current Profiler ◽  
Water Treatment Plant ◽  
Mean Flow ◽  
Cross Sectional ◽  
Flow Recirculation ◽  
Hydraulic Design

Abstract This paper presents a detailed characterization of turbulence in the incoming flow to the clarification component of a water treatment plant, ‘Los Molinos’ (Córdoba, Argentina). The main problems were related to the presence of turbulent flow patterns throughout the treatment, affecting the proper development of the physical processes required for water clarification. Namely: (a) a poor hydraulic design that could produce a non-homogeneous spatial distribution of the flow, recirculation zones and flow stagnation, and a non-uniform discharge distribution among the sedimentation units as a result of different cross-sectional dimensions of the transverse-channel, and (b) high turbulence intensity that affect the flocs' size as well as the efficiency of the settling tanks and filters. Firstly, a detailed in-situ experimental characterization of the turbulent flow was undertaken. An acoustic Doppler velocimeter (ADV) was used to characterize the flow turbulence, whereas for discharge measurements and mean flow velocity field an acoustic Doppler current profiler (ADCP) was employed. Secondly, a numerical model, based on the Reynolds-averaged Navier–Stokes (RANS) equations and the - turbulence closure model, was validated with the experimental data. Finally, based on the results, a diagnosis and recommendations were made for the optimization of the hydraulic design of the water treatment plant.

scholarly journals Erratum: Pauscher, L., et al. An Inter-Comparison Study of Multi- and DBS Lidar Measurements in Complex Terrain. Remote Sens. 2016, 8, 782

2017 ◽  
Vol 9 (7) ◽  
pp. 667 ◽  
Author(s):  
Lukas Pauscher ◽  
Nikola Vasiljevic ◽  
Doron Callies ◽  
Guillaume Lea ◽  
Jakob Mann ◽  
...  
Keyword(s):  
Complex Terrain ◽  
Comparison Study ◽  
Lidar Measurements

scholarly journals Geotechnical Characterization of the Subgrade on Some Rural Roads in Cross River State, Nigeria and the Influence of Geology

2020 ◽  
pp. 27-39
Author(s):  
Abidemi Olujide Ilori ◽  
Anusa Andrew Anusa
Keyword(s):  
Complex Terrain ◽  
Research Laboratory ◽  
Classification Scheme ◽  
American Association ◽  
Basement Complex ◽  
Rural Roads ◽  
Cross River ◽  
Cross River State ◽  
Geotechnical Characterization

The subgrades of three different rural roads alignment were investigated with the aim to determine their geotechnical properties. The three roads are on two different geologic terrains. Two of the roads, the 18 km Yahe-Waniye-Wanakom road and the 6 km Okpoma-Okuku road are on Cretaceous sediments terrain, while the 8 km Ugboro-Imaje-Okuku road is on the Basement Complex terrain. Based on American Association of Highways and Transportation Officials (AASHTO) most of the soils classify as A-2-4, A-2-6 on the first two roads with A-7-5, A-7-6 soils interspersed between the A-2-4 soils. The A-2-4, A-2-6 soils were also encountered on the only alignment on the basement complex, but the A-7 group of soils were not encountered on this alignment. Based on The Transport Research Laboratory Road Note 31, subgrade quality on all the three alignments is classed into ‘S4 to S6’ subgrade class. In this classification scheme ‘S6’ is the subgrade of the highest quality.

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