Lagrangian Coherent Structure Analysis of Terminal Winds Detected by Lidar. Part II: Structure Evolution and Comparison with Flight Data

2011 ◽  
Vol 50 (10) ◽  
pp. 2167-2183 ◽  
Author(s):  
Wenbo Tang ◽  
Pak Wai Chan ◽  
George Haller
Keyword(s):  
Coherent Structures ◽  
Coherent Structure ◽  
Wind Shear ◽  
Light Detection And Ranging ◽  
Structure Evolution ◽  
Flow Structures ◽  
Lidar Data ◽  
Lagrangian Coherent Structure ◽  
Flight Data ◽  
Hong Kong International Airport

AbstractUsing observational data from coherent Doppler light detection and ranging (lidar) systems situated at the Hong Kong International Airport (HKIA), the authors extract Lagrangian coherent structures (LCS) intersecting the flight path of landing aircraft. They study the time evolution of LCS and compare them with onboard wind shear and altitude data collected during airplane approaches. Their results show good correlation between LCS extracted from the lidar data and updrafts and downdrafts experienced by landing aircraft. Overall, LCS analysis shows promise as a robust real-time tool to detect unsteady flow structures that impact airplane traffic.

scholarly journals Lagrangian Coherent Structure Analysis of Terminal Winds: Three-Dimensionality, Intramodel Variations, and Flight Analyses

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Brent Knutson ◽  
Wenbo Tang ◽  
Pak Wai Chan
Keyword(s):  
Coherent Structures ◽  
Three Dimensional ◽  
Light Detection And Ranging ◽  
Flow Structures ◽  
Lidar Data ◽  
Two Dimensional ◽  
Lagrangian Coherent Structure ◽  
Flight Data ◽  
Velocity Information ◽  
Hong Kong International Airport

We present a study of three-dimensional Lagrangian coherent structures (LCS) near the Hong Kong International Airport and relate to previous developments of two-dimensional (2D) LCS analyses. The LCS are contrasted among three independent models and against 2D coherent Doppler light detection and ranging (LIDAR) data. Addition of the velocity information perpendicular to the LIDAR scanning cone helps solidify flow structures inferred from previous studies; contrast among models reveals the intramodel variability; and comparison with flight data evaluates the performance among models in terms of Lagrangian analyses. We find that, while the three models and the LIDAR do recover similar features of the windshear experienced by a landing aircraft (along the landing trajectory), their Lagrangian signatures over the entire domain are quite different—a portion of each numerical model captures certain features resembling those LCS extracted from independent 2D LIDAR analyses based on observations.

Lagrangian Coherent Structure Analysis of Terminal Winds Detected by Lidar. Part I: Turbulence Structures

2011 ◽  
Vol 50 (2) ◽  
pp. 325-338 ◽  
Author(s):  
Wenbo Tang ◽  
Pak Wai Chan ◽  
George Haller
Keyword(s):  
Coherent Structures ◽  
Finite Domain ◽  
Lidar Data ◽  
Commercial Aviation ◽  
Turbulence Structures ◽  
Finite Time Lyapunov Exponent ◽  
Turbulent Airflow ◽  
Vertical Slice ◽  
Convergence And Divergence ◽  
Hong Kong International Airport

Abstract The accurate real-time detection of turbulent airflow patterns near airports is important for safety and comfort in commercial aviation. In this paper, a method is developed to identify Lagrangian coherent structures (LCS) from horizontal lidar scans at Hong Kong International Airport (HKIA) in China. LCS are distinguished frame-independent material structures that create localized attraction, repulsion, or high shear of nearby trajectories in the flow. As such, they are the fundamental structures behind airflow patterns such as updrafts, downdrafts, and wind shear. Based on a recently developed finite-domain–finite-time Lyapunov exponent (FDFTLE) algorithm from Tang et al. and on new Lagrangian diagnostics presented in this paper that are pertinent to the extracted FDFTLE ridges, the authors differentiate LCS extracted from lidar data. It is found that these LCS derived from horizontal lidar scans compare well to convergence and divergence suggested by vertical slice scans. At HKIA, horizontal scans are predominant: they cover much bigger azimuthal ranges as compared with only two azimuthal angles from the vertical scans. LCS extracted from horizontal scans are thus advantageous in providing organizing turbulence structures over the entire observational domain as compared with a single line along the vertical scan direction. In Part II of this study, the authors will analyze the evolution of LCS and their impacts on landing aircraft based on recorded flight data.

Lagrangian Detection of Wind Shear for Landing Aircraft

2013 ◽  
Vol 30 (12) ◽  
pp. 2808-2819 ◽  
Author(s):  
Hossein Amini Kafiabad ◽  
Pak Wai Chan ◽  
George Haller
Keyword(s):  
Lyapunov Exponent ◽  
Coherent Structures ◽  
Wind Shear ◽  
Particle Dynamics ◽  
Spring Season ◽  
Multiple Sources ◽  
Alert System ◽  
Finite Time Lyapunov Exponent ◽  
Ground Based Lidar ◽  
Hong Kong International Airport

Abstract Recent studies have shown that aerial disturbances affecting landing aircraft have a coherent signature in the Lagrangian aerial particle dynamics inferred from ground-based lidar scans. Specifically, attracting Lagrangian coherent structures (LCSs) mark the intersection of localized material upwelling within the cone of the lidar scan. This study tests the detection power of LCSs on historical landing data and corresponding pilot reports of disturbances from Hong Kong International Airport. The results show that a specific LCS indicator, the gradient of the finite-time Lyapunov exponent (FTLE) field along the landing path, is a highly efficient marker of turbulent upwellings. In particular, in the spring season, projected FTLE gradients closely approach the efficiency of the wind shear alert system currently in operation at the airport, even though the latter system relies on multiple sources of data beyond those used in this study. This shows significant potential for the operational use of FTLE gradients in the real-time detection of aerial disturbances over airports.

scholarly journals Experimental Study on Coherent Structures by Particles Suspended in Half-Zone Thermocapillary Liquid Bridges: Review

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 105
Author(s):  
Ichiro Ueno
Keyword(s):  
Coherent Structures ◽  
Three Dimensional ◽  
Wave Number ◽  
Flow Structures ◽  
Liquid Bridges ◽  
Thermocapillary Effect ◽  
Particle Accumulation ◽  
Azimuthal Wave Number ◽  
Experimental Approaches ◽  
Particle Behaviour

Coherent structures by the particles suspended in the half-zone thermocapillary liquid bridges via experimental approaches are introduced. General knowledge on the particle accumulation structures (PAS) is described, and then the spatial–temporal behaviours of the particles forming the PAS are illustrated with the results of the two- and three-dimensional particle tracking. Variations of the coherent structures as functions of the intensity of the thermocapillary effect and the particle size are introduced by focusing on the PAS of the azimuthal wave number m=3. Correlation between the particle behaviour and the ordered flow structures known as the Kolmogorov–Arnold—Moser tori is discussed. Recent works on the PAS of m=1 are briefly introduced.

scholarly journals Analysis and Prediction of Gap Dynamics in a Secondary Deciduous Broadleaf Forest of Central Japan Using Airborne Multi-LiDAR Observations

2020 ◽  
Vol 13 (1) ◽  
pp. 100
Author(s):  
Kazuho Araki ◽  
Yoshio Awaya
Keyword(s):  
Linear Regression Analysis ◽  
Light Detection And Ranging ◽  
Lidar Data ◽  
Gap Dynamics ◽  
Central Japan ◽  
Broadleaf Forest ◽  
Strong Linear Correlation ◽  
Using Data ◽  
Deciduous Broadleaf Forest ◽  
Lidar Observations

Gaps are important for growth of vegetation on the forest floor. However, monitoring of gaps in large areas is difficult. Airborne light detection and ranging (LiDAR) data make precise gap mapping possible. We formulated a method to describe changes in gaps by time-series tracking of gap area changes using three digital canopy height models (DCHMs) based on LiDAR data collected in 2005, 2011, and 2016 over secondary deciduous broadleaf forest. We generated a mask that covered merging or splitting of gaps in the three DCHMs and allowed us to identify their spatiotemporal relationships. One-fifth of gaps merged with adjacent gaps or split into several gaps between 2005 and 2016. Gap shrinkage showed a strong linear correlation with gap area in 2005, via lateral growth of gap-edge trees between 2005 and 2016, as modeled by a linear regression analysis. New gaps that emerged between 2005 and 2011 shrank faster than gaps present in 2005. A statistical model to predict gap lifespan was developed and gap lifespan was mapped using data from 2005 and 2016. Predicted gap lifespan decreased greatly due to shrinkage and splitting of gaps between 2005 and 2016.

scholarly journals A Novel Method for Feature Extraction and Classification for an Aerial Image and LiDAR Data with Genetic Algorithm

2012 ◽  
pp. 264-270
Author(s):  
Manjunath B. E ◽  
D. G. Anand ◽  
Mahant. G. Kattimani
Keyword(s):  
Feature Extraction ◽  
Light Detection And Ranging ◽  
Aerial Image ◽  
Lidar Data ◽  
Light Detection ◽  
Aerial Photos ◽  
The Earth ◽  
Digital Elevation ◽  
Land Surveying ◽  
Novel Method

Airborne Light Detection and Ranging (LiDAR) provides accurate height information for objects on the earth, which makes LiDAR become more and more popular in terrain and land surveying. In particular, LiDAR data offer vital and significant features for land-cover classification which is an important task in many application domains. Aerial photos with LiDAR data were processed with genetic algorithms not only for feature extraction but also for orthographical image. DSM provided by LiDAR reduced the amount of GCPs needed for the regular processing, thus the reason both efficiency and accuracy are highly improved. LiDAR is an acronym for Light Detection and Ranging, which is typically defined as an integration of three technologies into a single system, which is capable of acquiring a data to produce accurate Digital Elevation Models.

scholarly journals Lessons from LiDAR data use in the Netherlands

2017 ◽  
Vol 1 (2) ◽  
pp. 661-670 ◽  
Author(s):  
Willem Frans Beex
Keyword(s):  
The Netherlands ◽  
Best Practices ◽  
Cultural Heritage ◽  
Land Surface ◽  
New Technology ◽  
Data Use ◽  
Light Detection And Ranging ◽  
Lidar Data ◽  
Natural Land ◽  
Imaging Detection

Light Detection And Ranging or Laser Imaging Detection And Ranging (LiDAR) is not really a new technology. However, it does provide the data from which accurate models of the natural land surface completely stripped of buildings and vegetation can be derived. Interestingly for Cultural Heritage and Archaeology, most of the data is already freely available for research. This is certainly the case in the Netherlands, with the “Actueel Hoogtemodel Nederland 2”, or “AHN2”. The density of the measured points is at least 50 centimetres, which means that the remains of structures larger than one by one metre can be detected. As a result, many unknown structures have been discovered with it. However, these excellent results have blinded many Cultural Heritage and Archaeology practitioners to obvious mistakes when interpreting LiDAR data. This paper is intended to highlight best-practices for the use of LiDAR data by Cultural Heritage professionals.

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