Unsteady three-dimensional compressible vortex flows
Date
2010-08-11
Authors
Reeves, James Oliver
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Abstract
Vortex flows are fundamental to nature and technology. In this dissertation, the results of an
experimental and numerical investigation into the behaviour of the free vortex generated by shock
diffraction over edges yawed to the incident shock wave are presented. The objectives of this
study were to explore the behaviour of the free vortex in three dimensions, with a particular focus
on the distortions caused to the vortex by the presence of a solid boundary, or wall. Threedimensional
numerical simulations and experimentally obtained schlieren photographs reveal
significant distortion and bending of the free vortex in regions near the boundary of the flow
domain, so as to meet it at a right angle. Experimentation was performed in a shock tube for
incident shock Mach numbers of 1.32, 1.42, and 1.65, with four test models, two incorporating
straight diffraction edges, and two incorporating curved diffracting edges. Numerical simulation
was performed with Fluent 6.3.26 software. The numerical solutions were validated against the
experimental results through pictorial comparison, and despite relatively coarse meshes being
used, were found to mimic the experimental results very well. The numerical results are used
here to investigate and explain the various features of the resultant flow fields, with particular
emphasis placed on the behaviour and properties of the free vortex. The effects of bending on the
structure of the vortex and on the flow properties with the vortex are examined. The rate of
circulation production for the three-dimensional diffraction cases was calculated, and the trends
observed correlated with those for the much published two-dimensional diffraction case. Also
investigated is the three-dimensional shock diffraction case, where it was found that the shape of
the diffracted shock wave differed slightly from the two-dimensional case in the region near the
boundaries of the domain.