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Author(s): S. Benteboula & G. Lauriat
Abstract:
This work aims at developing computing tools for the numerical simulation of
impulsively started jets with variable physical properties due to large thermal
gradients.
The fluid is injected at temperature Tj and density ρj in a quiescent
surroundings at different temperature and density Ta, ρa.
The 3D-time dependent
Navier–Stokes equations, formulated in the low Mach number approximation,
were numerically integrated by using a non divergence-free projection method.
The computations were performed for 3D and axisymmetric jets, and for a wide
range of the jet-to-ambient density ratio, α = ρj /ρa, providing the expected flow
features.
Except the formation of a leading vortex in the head of the flow followed
by a jet stem, the results show that the behaviour and the dynamics are quite
different for hot and cold jets.
The hot jet is indeed characterised by a leading
vortex in which the hotter fluid is concentrated, while the vortex ring is a region of
intermediate temperature and density for a cold jet.
Particular attention is given to
the influence of α on the integral characteristics of vortex rings such as circulation
and impulse.
Keywords:
numerical simulation, anisothermal vortex ring, low mach number flow,
variable density.
1 Introduction:
The fluid injection through an orifice or a nozzle in a stagnant atmosphere leads
to the generation of a vortex ring followed by a tail.
Vortex rings are encountered
...
Pages: 9
Size: 1,548 kb
Paper DOI: 10.2495/AFM080401
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