Identification of vortex pairs in aircraft wakes from sectional velocity data

Abstract

The dynamics of multiple-vortex wake systems behind aircraft endangering air traffic can be assessed also from physical modelling. Large-scale laboratory investigations of multiple-vortex systems have been performed in a free-flight laboratory and in a water towing tank. Specialized PIV measurements provide time-resolved flow velocity fields normal to the wake axis. The applicability of various ∇u-based vortex identification schemes to planar velocity data is addressed and demonstrated for unequal-strength co- and counter-rotating vortex pairs. Large vortices shed off the wing tips and flaps are identified employing a ∇u-based criterion. Their cooperative mechanisms of generation and decay are evidenced from iso-surfaces of squared swirling strength and from further characteristic vortex parameters.

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Notes

  1. 1.

    The two-dimensional Weiss formulation (3) of the Q criterion shows an opposite sign with respect to the general definition of a positive second invariant (2).

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Acknowledgments

C.F.C. and R.K. are indebted to the joint ONERA/DLR expert group comprising J. Agocs, E. Brunel, K. Christou, P. Coton, J.-P. Evard, C. Fatien, H. Frahnert, C. Geiler, A. Gilliot, A. Heider, H. Mattner, J.-C. Monnier, A. Schröder, P. Simon, and D. Thibaut for preparing and conducting the catapult measurements, and to A. Heider for his assistance in performing the PIV evaluation (Sect. 3). F. Bao and H. Vollmers provided the PIV data of the towing tank measurements (Sect. 4). The authors wish to thank A. de Bruin and E. Coustols for their useful information and helpful remarks. The support of the European Commission co-funding the AWIATOR project in its 5th framework program is gratefully acknowledged.

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Correspondence to Carl F. v. Carmer.

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Carmer, C.F.v., Konrath, R., Schröder, A. et al. Identification of vortex pairs in aircraft wakes from sectional velocity data. Exp Fluids 44, 367–380 (2008). https://doi.org/10.1007/s00348-007-0450-8

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Keywords

  • Vortex
  • Particle Image Velocimetry
  • Vortex Core
  • Vortical Structure
  • Particle Image Velocimetry Measurement