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Turbulence and Shear Flow Phenomena -1 First International Symposium

ISBN:
1-56700-135-1 (Print)

TURBULENT SCALAR MIXING IN COAXIAL JET FLOWS

Paulo C. Ferrao
Mechanical Engineering Department Instituto Superior Tecnico Av. Rovisco Pais, 1049-001 Lisboa Technical University of Lisbon Portugal

Manuel V. Heitor
Instituto Superior Técnico, Technical University of Lisbon, Department of Mechanical Engineering, Av. Rovisco Pais, 1096 Lisboa, Codex, Portugal

Mario F. de Matos
Mechanical Engineering Department Instituto Superior Tecnico Av. Rovisco Pais, 1049-001 Lisboa Technical University of Lisbon Portugal

Renato K. Salles
Mechanical Engineering Department Instituto Superior Tecnico Av. Rovisco Pais, 1049-001 Lisboa Technical University of Lisbon Portugal

Abstract

The turbulent characteristics of the developing region of an axisymmetric coaxial jet of C02 (Rei= 15000) and air (Reo=50000) are analysed making use of experimental results obtained in the initial region where most of the mixing takes place. Time-resolved velocity and scalar fields were characterised by laser Doppler velocimetry and laser Rayleigh scattering, while the instantaneous velocity field was analysed with double-exposure photographic particle image velocimetry. Linear imaging of laser Rayleigh scattering was used to acquire instantaneous information about the scalar field that enables the quantification of scalar dissipation. As a result, scalar dissipation distribution can be associated to the evolution of the Reynolds stresses along the jet and the later is related to the location of large-scale structures, which are identified with the locus of maximum vorticity.