The mechanism of entrainment in circular jets

Mathew, Joseph and Basu, Amit J (1994) The mechanism of entrainment in circular jets. In: 14th International Conference on Numerical Methods in Fluid Dynamics, 11-15 Jul 1994, Bangalore, India.

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Abstract

The evolution to turbulence of a thin circular mixing-layer (jetlike flow) was computed using a Fourier-spectral, fourth-order predictor-corrector scheme. Data for Reynolds number (based on initial jet-diameter and velocity difference across shear layer) of 1600 on a 64 exp 3 grid and 2400 on a 128 exp 3 grid were used to study the fluxes associated with entrainment to the turbulent region. The flux that leads to a growth in the size of the region is but slightly larger than that which leads to its reduction. The data suggest that engulfment is therefore an incomplete picture of turbulent entrainment. A fluid packet is drawn to the turbulent region by the vorticity, entering and leaving it several times as it acquires vorticity by viscous diffusion. The entraining flows are strong and clearly associated with vortex rings at early times, but following ring-breakdown, clear organization on the largest scales is not found. Plots of the vorticity and velocity fields do suggest organization on intermediate scales (thickness of vortical structures).

Item Type: Conference or Workshop Item (Paper)
Uncontrolled Keywords: Jet flow;Mixing layers(fluids);Flow geometry
Subjects: ENGINEERING > Fluid Mechanics and Thermodynamics
Division/Department: Flosolver Division, Flosolver Division
Depositing User: M/S ICAST NAL
Date Deposited: 06 Aug 2008
Last Modified: 24 May 2010 09:50
URI: http://nal-ir.nal.res.in/id/eprint/2785

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