Mixing layer: Numerical and experimental control strategies

Jesse C Little, Upender K. Kaul

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This study focuses on a numerical investigation of a mixing layer vis-a-vis an experimental study using dielectric barrier discharge (DBD) plasma actuators.1 Upstream perturbations from the experiment1-3 are imposed as inflow boundary condition in the direct numerical simulation (DNS) of the mixing layer using a computational methodology reported recently.4;5 Development of the mixing layer is followed computationally through the initial stages of coalescence of vortex structures. This collaborative investigation is unique and has shed some light on the mechanism of the coalescence process of the coherent structures in the mixing layer. For example, in experiments,1;2 it was observed that AC-DBD plasma actuation using high voltage (15kV) 30 Hz 50 per cent duty cycle pulses produced more energetic growth of the mixing layer than a pure sine mode. In the DNS carried out here, it is shown that the growth of the mixing layer corresponding to the inflow conditions provided by this experiment appears to be characterized by a new type of interaction (rather than a binomial process of pairing), where a paired and a nascent rolled-up structure coalesce. This “joint interaction” does not appear to be the “collective interaction” that has been observed experimentally6 or computationally.4;5 This joint interaction leads to an enhanced growth of the mixing layer in comparison to a pairing4;5 and provides a physical reason for the experimental observation1-3 that the growth in this case is more energetic. The purpose of this effort is to enable a collaborative platform to identify various deterministic startegies for controlling the growth of a free shear layer or mixing layer, which are found in a variety of engineering applications. Vorticity thicknesss and momentum thickness evolution in the mixing layer are predicted, the latter compared with the experimental results.1-3 DNS predictions agree reasonably well with experiments, but some differences are apparent. In essence, the effect of the wind tunnel on the mixing layer behavior is not captured in the DNS since no-slip boundary conditions, freestream turbulence and effect of the diffuser are not enforced. Comparison of Reynolds shear stress at various streamwise locations indicates local regions in which turbulence transfers energy back to the mean flow, a reverse cascade energy transfer mechanism, as observed experimentally.1-3 This study is unique and has potential for furthering this collaborative platform for the purpose of mixing layer flow control.

Original languageEnglish (US)
Title of host publication45th AIAA Fluid Dynamics Conference
PublisherAmerican Institute of Aeronautics and Astronautics Inc, AIAA
ISBN (Print)9781624103629
StatePublished - 2015
Event45th AIAA Fluid Dynamics Conference, 2015 - Dallas, United States
Duration: Jun 22 2015Jun 26 2015

Other

Other45th AIAA Fluid Dynamics Conference, 2015
CountryUnited States
CityDallas
Period6/22/156/26/15

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Keywords

  • DBD
  • DNS
  • Flow control
  • Free shear layer
  • Mixing layer

ASJC Scopus subject areas

  • Engineering (miscellaneous)
  • Aerospace Engineering

Cite this

Little, J. C., & Kaul, U. K. (2015). Mixing layer: Numerical and experimental control strategies. In 45th AIAA Fluid Dynamics Conference American Institute of Aeronautics and Astronautics Inc, AIAA.