An Observational Study of Vortex Spacing in Island Wake Vortex Streets

Young, George S.; Zawislak, Jonathan

doi:10.1175/mwr3186.1

Cited by 47 publications

(52 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…1), with isolated areas of enhanced shear located within them. This flow pattern is qualitatively consistent with past modeling studies of weakened environmental flow and wake vortices produced downstream of isolated terrain maxima (e.g., Schar and Smith, 1993a, b;Sun and Chern, 1994;Schar and Durran, 1997;Young and Zawislak, 2006). However, there are only a few detailed observational studies of such wake flow in the literature.…”

Section: Introductionsupporting

confidence: 89%

LIDAR ground-based velocity track display analyses and surface observations of a vortex shedding event observed at the Hong Kong International Airport on April 11, 2011

Chan¹,

Wurman²,

Robinson³

2017

Atm

View full text Add to dashboard Cite

RESUMENCerca de la isla de Lantau, contigua al Aeropuerto Internacional de Hong Kong, se observan vórtices fragmentados que pueden poner en peligro las operaciones aéreas en dicha terminal. Se efectúa un análisis detallado de la estructura de un vórtice fragmentado mediante observaciones de superficie, así como, análisis de datos de un dispositivo Doppler para medición de luz y distancia (LIDAR, por sus siglas en inglés) con el algoritmo para cálculo de vientos GBVTD (ground-based velocity track display). Este análisis exhaustivo de datos de superficie muestra la presencia de irregularidades del viento que ocurrieron simultáneamente al paso de los vórtices. Los vientos simulados con un modelo idealizado de vórtice, desarrollado a partir de las propiedades de cada vórtice estimadas con LIDAR, se ajustan adecuadamente a las observaciones de viento y presión obtenidas por las boyas meteorológicas. Los datos analizados con el algoritmo GBVTD indican la presencia de convergencia radial y movimiento vertical casi en todo momento durante el ciclo de vida de los vórtices. Este trabajo busca documentar la estructura tridimensional de dichos vórtices fragmentados por las montañas, lo que podría ser de utilidad para la seguridad aérea con relación a la detección, evitación y recuperación de cizallamientos de viento, en aeropuertos con características de terreno similares. ABSTRACTVortex shedding occurs downstream of Lantau Island over the Hong Kong International Airport and can be hazardous to aircraft operating from that airport. An in-depth analysis of a vortex shedding structure is conducted using surface observations and Ground-Based Velocity Track Display (GBVTD) analysis of the Doppler Light Detection and Ranging (LIDAR) data. This in-depth examination of the surface data indicates that brief wind anomalies were observed simultaneously with the passage of the vortices. Winds simulated using an idealized vortex model constructed using LIDAR-estimated properties of each vortex fit reasonably well with the weather buoy wind and pressure observations. GBVTD retrievals indicate radial convergence and upward motion at most times throughout the lifecycle of the vortices. This paper aims to document the three-dimensional structure of such vortices shedded from the mountains, which may be useful for aviation safety involving wind shear detection, avoidance and recovery at airports with similar terrain features nearby.

show abstract

Section: Introductionsupporting

confidence: 89%

LIDAR ground-based velocity track display analyses and surface observations of a vortex shedding event observed at the Hong Kong International Airport on April 11, 2011

Chan¹,

Wurman²,

Robinson³

2017

Atm

View full text Add to dashboard Cite

show abstract

“…It is also interesting to remark that the spacing ratio of atmospheric vortex streets in the wake of mountains or islands is typically 0.3-0.4 (Etling 1989(Etling , 1990Li et al 2000;Young & Zawislak 2006), i.e. in the range unstable to the zigzag instability.…”

Section: Resultsmentioning

confidence: 99%

Three-dimensional stability of vortex arrays in a stratified and rotating fluid

2011

View full text Add to dashboard Cite

International audienceThis paper investigates numerically and through an asymptotic approach the three-dimensional stability of steady vertical vortex arrays in a stratified and rotating fluid. Three classical vortex arrays are studied: the KÃ¡rmÃ¡n vortex street, the symmetric double row and the single row of co-rotating vortices. The asymptotic analysis assumes well-separated vortices and long-wavelength bending perturbations following Billant (J. Fluid Mech., vol. 660, 2010, p. 354) and Robinson & Saffman (J. Fluid Mech., vol. 125, 1982, p. 411). Very good agreement with the numerical stability analysis is found even for finite wavelength and relatively close vortices. For a horizontal Froude number Fh = 1 and for a non-rotating fluid, it is found that the Kármán vortex street for a street spacing ratio (the distance h between the rows divided by the distance b between vortices in the same row) ? = 0.41 and the symmetric double row for any spacing ratio are most unstable to a three-dimensional instability of zigzag type that vertically bends the vortices. The most amplified vertical wavenumber scales like 1/(bFh) and the growth rate scales with the strain (2pb2), where is the vortex circulation. For the Kármán vortex street, the zigzag instability is symmetric with respect to the midplane between the two rows while it is antisymmetric for the symmetric double row. For the Kármán vortex street with well-separated vortex rows ? > 0.41 and the single row, the dominant instability is two-dimensional and corresponds to a pairing of adjacent vortices of the same row. The main differences between stratified and homogeneous fluids are the opposite symmetry of the dominant three-dimensional instabilities and the scaling of their most amplified wavenumber. When Fh > 1, three-dimensional instabilities are damped by a viscous critical layer. In the presence of background rotation in addition to the stratification, symmetric and antisymmetric modes no longer decouple and cyclonic vortices are less bent than anticyclonic vortices. However, the dominant instability remains qualitatively the same for the three vortex arrays, i.e. quasi-symmetric or quasi-antisymmetric and three-dimensional or two-dimensional. The growth rate continues to scale with the strain but the most unstable wavenumber of three-dimensional instabilities decreases with rotation and scales like Ro/(bFh) for small Rossby number Ro, in agreement with quasi-geostrophic scaling laws. © 2011 Cambridge University Press

show abstract

“…1) is an atmospheric eddy produced by marine atmospheric boundary layer (MABL) flow past terrain. Such eddies form as part of an atmospheric wake phenomenon in the lee of islands and headlands that penetrate the inversion above the MABL (Chopra and Hubert 1965;Etling 1989;Young and Zawislak 2006). Mesoscale eddies have been detected in satellite imagery in marine stratocumulus clouds since the first successful weather satellite was launched in 1960 (Bowley et al 1962;Hubert and Krueger 1962).…”

Section: Introductionmentioning

confidence: 99%

“…In other cases an alternating series of counter-rotating vortices form and shed, moving downwind with the mean MABL flow (Schär and Smith 1993b). Some researchers consider these circulations to be the atmospheric analog of von Kármán vortex streets that appear as fluids flow past bluff bodies (Chopra and Hubert 1965;Ruscher and Deardorff 1982;Young and Zawislak 2006).…”

Section: Introductionmentioning

confidence: 99%