Vortex dynamics behind cruising aircraft studied by a ground-based scanning lidar and airborne in-situ measurements

Ralf Sussmann; Horst Jaeger

doi:10.1117/12.275153

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26 May 1997 Vortex dynamics behind cruising aircraft studied by a ground-based scanning lidar and airborne in-situ measurements

Ralf Sussmann; Horst Jaeger

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Proceedings Volume 3104, Lidar Atmospheric Monitoring; (1997) https://doi.org/10.1117/12.275153
Event: Environmental Sensing III, 1997, Munich, Germany

Abstract

By LIDAR and CCD camera analysis the geometrical evolution of a vortex phase contrail (descent rate V_d equals 2.7 m/s, vortex separation D equals 47 m, vertical extension (sigma) _z equals 140 m after 77 s) is analyzed. The contrail of a four-engine aircraft is showing a diffuse central wake phenomenon. From coincident in situ measurements all relevant meteorological parameters are characterized. Ambient humidity had been close to ice saturation. From this a non-exhaust formation of ice can be excluded. Also the mechanism of non- entrainment of exhaust into the vortices is excluded of being responsible for the observed early onset of the central wake (870 m behind aircraft). The central wake onset originates from early detrainment starting after a 3/4 roll-up period of the vortex. Baroclinic and shear forces do not contribute to the detrainment (imaginary Brunt-Vaisala-frequency N² equals negative 3 multiplied by 10^-5 s^-2, shear dS/dz equals negative 0.01 s^-1, bulk Richardson number R_i, equals N²/(dS/dz)² equals negative 0.3). Ambient turbulence had been fully developed with an inertial range and locally isotropic turbulence for wavenumbers k-equals 0.004 - 0.1 radian/m. The eddy dissipation rate (epsilon) equals 7.4 plus or minus 0.5 multiplied by 10^-5 m²s^-3 exceeds the values found over the North Atlantic flight corridor at cruising altitude by a factor of 1000. Turbulence was identified as the dominating detrainment mechanism.

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Ralf Sussmann and Horst Jaeger "Vortex dynamics behind cruising aircraft studied by a ground-based scanning lidar and airborne in-situ measurements", Proc. SPIE 3104, Lidar Atmospheric Monitoring, (26 May 1997); https://doi.org/10.1117/12.275153

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