Journal of Fluid Science and Technology
Online ISSN : 1880-5558
ISSN-L : 1880-5558
Papers
Analysis of Flow Characteristics of Turbulent Plane Jets Based on Velocity and Scalar Fields Using DNS
Nannan WUYasuhiko SAKAIKouji NAGATAHiroki SUZUKIOsamu TERASHIMAToshiyuki HAYASE
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2013 Volume 8 Issue 3 Pages 247-261

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Abstract

Turbulent plane jets are prototypical free shear flows on which fundamental research can expand the overall understanding of turbulent flows. In this study, flow characteristics of the turbulent plane jets are studied by means of direct numerical simulation (DNS) based on the finite difference method. The effects of the initial conditions at the jet exit (i.e. Reynolds number and velocity profile) on the spatial development of velocity and scalar fields are mainly investigated. Meanwhile the instantaneous coherent structures, based on the Q-criterion and the local minimum of pressure, are presented. The results suggest that the plane jet flow with the higher Re (=Ubd/ν : Ub is the bulk mean velocity at the jet exit, d is the slot width, and ν is the kinematic viscosity) and the parabola velocity profile at the jet exit will correspond to the shorter potential core, furthermore, the lower Re and the parabola velocity profile will strengthen the decay of the mean field in the process of flow transition to full turbulence. The flow self-similarity will be achieved at shorter streamwise distance from the jet exit for the higher Re and the parabola velocity profile at the jet exit. Moreover, the dependency of coherent structures on the initial Reynolds number is remarkable, especially in the flow development region, but the change of initial velocity profile at the jet exit hardly acts on the scale of coherent structures. It is also observed that the scalar field is more sensitive to changes of initial conditions than the velocity field.

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© 2013 by The Japan Society of Mechanical Engineers
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