Optimal Deployment of Drifting Acoustic Sensors: Sensitivity of Lagrangian Coherent Structure Boundaries to Model Uncertainty

2007 ◽  
Author(s):  
A. C. Poje
Keyword(s):  
Coherent Structure ◽  
Model Uncertainty ◽  
Acoustic Sensors ◽  
Lagrangian Coherent Structure ◽  
Optimal Deployment

Lagrangian Analysis of Unsteady Partial Cavitating Flow Around a Three-Dimensional Hydrofoil

2020 ◽  
Author(s):  
Tingyun Yin ◽  
Giorgio Pavesi ◽  
Ji Pei ◽  
Shouqi Yuan ◽  
Giovanna Cavazzini ◽  
...  
Keyword(s):  
Coherent Structure ◽  
Cavity Growth ◽  
Three Dimensional ◽  
Adverse Pressure Gradient ◽  
Buffer Zone ◽  
Cavitating Flow ◽  
Lagrangian Analysis ◽  
Lagrangian Coherent Structure ◽  
Cavity Development ◽  
Unsteady Cavitating Flow

Abstract This study employs an incompressible homogeneous flow framework with a transport-equation-based cavitation model and shear stress transport turbulence model to successfully reproduce the unsteady cavitating flow around a three-dimensional hydrofoil. Cavity growth, development, and break-off during the periodic shedding process are adequately reproduced and match experimental observations. The predicted shedding frequency is very close to the experimental value of 23 ms. By monitoring the motions of the seeding trackers, growth-up of attached cavity and dynamic evolution of U-type cavity are clearly displayed, which indicating the trackers could serve as an effective tool to visualize the cavitating field. Repelling Lagrangian Coherent Structure (RLCS) is so complex that abundant flow patterns are highlighted, reflecting the intricacy of cavity development. The formation of cloud cavities is clearly characterized by the Attracting Lagrangian Coherent Structure (ALCS), where bumbling wave wrapping the whole shedding cavities indicates the rotating transform of cavities and stretching of the wave eyes shows the distortion of vortices. Generation of the re-entrant jet is considered to be not only associated with the adverse pressure gradient due to the positive attack angle, but also the contribution of cloud cavitating flow, based on the observation of a buffer zone between the attached and cloud cavities.

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.

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