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THE STRUCTURE OF A TURBULENT AXISYMMETRIC JET VIA A VECTOR IMPLEMENTATION OF THE PROPER ORTHOGONAL DECOMPOSITION

Flint O. Thomas
Center for Flow Physics and Control, University of Notre Dame, Notre Dame, IN 46556, USA

Muhammad O. Iqbal
Center for Flow Physics and Control, University of Notre Dame, Notre Dame, IN 46556, USA

Thomas C. Corke
Center for Flow Physics and Control, University of Notre Dame, Notre Dame, IN 46556, USA

Abstract

In this paper the large-scale structure of a high Reynolds number axisymmetric turbulent jet is characterized experimentally by an implementation of the proper orthogonal decomposition (POD) that utilizes all three fluctuating velocity components. The focus of the work is on the structure in the near-field of the jet due to its importance in numerous technical applications. POD eigenspectra provide the modal energy distribution as a function of both temporal frequency (or Strouhal number) and azimuthal mode number. The paper documents the streamwise evolution of the distribution of energy with azimuthal mode number. Differences arising between scalar and vector implementations of the POD are highlighted. Upstream of the tip of the jet core, the eigenspectra are found to exhibit peak amplitude at a constant Strouhal number based on local mean velocity and momentum thickness for a given azimuthal mode number.