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Large Eddy Simulation of Aircraft Wake Vortices in a Homogeneous Atmospheric Turbulence: Vortex Decay and DescentThe effects of ambient turbulence on decay and descent of aircraft wake vortices are studied using a validated, three-dimensional: large-eddy simulation model. Numerical simulations are performed in order to isolate the effect of ambient turbulence on the wake vortex decay rate within a neutrally-stratified atmosphere. Simulations are conducted for a range of turbulence intensities, by injecting wake vortex pairs into an approximately homogeneous and isotropic turbulence field. The decay rate of the vortex circulation increases clearly with increasing ambient turbulence level, which is consistent with field observations. Based on the results from the numerical simulations, simple decay models are proposed as functions of dimensionless ambient turbulence intensity (eta) and dimensionless time (T) for the circulation averaged over a range of radial distances. With good agreement with the numerical results, a Gaussian type of vortex decay model is proposed for weak turbulence: while an exponential type of Tortex decay model can be applied for strong turbulence. A relationship for the vortex descent based on above vortex decay model is also proposed. Although the proposed models are based on simulations assuming neutral stratification, the model predictions are compared to Lidar vortex measurements observed during stable, neutral, and unstable atmospheric conditions. In the neutral and unstable atmosphere, the model predictions appear to be in reasonable agreement with the observational data, while in the stably-stratified atmosphere, they largely underestimate the observed circulation decay with consistent overestimation of the observed vortex descent. The underestimation of vortex decay during stably-stratified conditions suggests that stratification has an important influence on vortex decay when ambient levels of turbulence are weak.
Document ID
20040086791
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Han, Jongil (North Carolina State Univ. Raleigh, NC, United States)
Lin, Yuh-Lang (North Carolina State Univ. Raleigh, NC, United States)
Arya, S. Pal (North Carolina State Univ. Raleigh, NC, United States)
Proctor, Fred H. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 1999
Subject Category
Aerodynamics
Report/Patent Number
AIAA Paper 99-0756
Meeting Information
Meeting: 37th AIAA Aerospace Sciences Meeting and Exhibit
Location: Reno, NV
Country: United States
Start Date: January 11, 1999
End Date: January 14, 1999
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
CONTRACT_GRANT: NAS1-18925
CONTRACT_GRANT: NCC1-188
Distribution Limits
Public
Copyright
Public Use Permitted.

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