Publication: Direct numerical simulation of the flow around an array of cylinders
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2014
Defense date
2014-09-30
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Abstract
In this project, the topic involves alternate vortex shedding from a cylindrical body
of circular cross section (also known as Von Karman vortex street) and the complex flow
patterns formed when interacting with other bodies and/or the proximity to a plane wall.
Vortex shedding takes place when the Reynolds number goes past the critical value of
the flow moving past a particular body. This project has made use of a Direct Numerical Simulation to solve the fluid dynamic
problem of flow past circular cylinders in tandem in the proximity of a plane wall. The
key parameters, responsible for the aerodynamic forces fluctuations and the variations in
vortex shedding frequency (Strouhal number), have been combined to produce different
problem configurations to achieve a better understanding of the interactions between
bodies and the proximity to a free-slip wall.
The evaluation of the Strouhal number shows that the single cylinder configuration
has a higher shedding frequency than the tandem configuration. In addition, the Strouhal
number increases with increasing Reynolds numbers.
The complex flow patterns developed with the proximity to a plane wall have also
been analyzed. For instance, with a constant longitudinal separation (L=D = 4), the flow
pattern changes as the cylinders get closer to the wall from shear-layer reattachment to
extended body regime. This shows that there is a critical point of the separation to the
wall that achieves vortex shedding suppression for the first and/or the second cylinder, as
a function of the Reynolds. Thus, the confinement effect and the low Reynolds number
are the key parameters in this particular phenomena.
The proximity to the wall affects the mean value of the forces, as they increase the
closer the bodies are with respect to the wall. The fluctuations on the aerodynamic
forces are produced by the shedding of vortices. The distance from the body to the
beginning of the vortex shedding is related to the amplitude. The closer to the body,
the higher the amplitude.
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Mecánica de fluidos, Análisis numérico, Fluctuaciones, Aeronáutica, Cilindros