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Scaling the Near-Field Centerline Mixing Behavior of Axisymmetric Turbulent Jets.


pdf icon Scaling the Near-Field Centerline Mixing Behavior of Axisymmetric Turbulent Jets. (1010 K)
Papadopoulos, G.; Pitts, W. M.

AIAA Journal, Vol. 36, No. 9, 1635-1642, September 1998.

Keywords:

turbulent jets; density effects; flow measurement; Rayleigh light scattering; turbulence; turbulent flow

Abstract:

Detailed measurements of the centerline mixing behavior in the near field of varible-density jets were performed. Real-time measurements of jet fluid concentration for a propane jet and a methane jet issuing into still air were made utilizing Rayleigh light scattering. The initial conditions were those of fully developed pipe flow, and testing was done for flow rates yeilding Reynolds numbers in the range of 3.3 x 103-2.3 x 104, based on the average discharge velocity, exit diameter, and initial fluid properties. Centerline decay characteristics in the near field exhibited a downstream shift with increasing Reynolds number, which was attributed to the initial velocity distribution at the jet exit. Investigation of the mean and turbulent characteristics of the initial velocity distribution yielded a proposed near-field scale variable that effectively captured this dependence on Reynolds nyumber. Collapse of the near-field centerline velocity and concentrations distributions was achieved using the proposed scaling.