Investigation of flow past various shape bluff bodies at low reynolds number
Two-dimensional flow over bluff bodies of different shapes is studied in the laminar regime. Different shapes are created by altering the rear part of a circular cylinder where flow separation occurs. In order to create a more streamlined body, the rear portion of a circular cylinder is changed f...
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| Format: | Theses and Dissertations |
| Language: | English |
| Published: |
2016
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| Subjects: | |
| Online Access: | http://hdl.handle.net/10356/68660 |
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| Institution: | Nanyang Technological University |
| Language: | English |
| Summary: | Two-dimensional flow over bluff bodies of different shapes is studied in the laminar
regime. Different shapes are created by altering the rear part of a circular cylinder
where flow separation occurs. In order to create a more streamlined body, the rear
portion of a circular cylinder is changed from that of a circular arc to an elliptical one
with semi major axis greater than the radius of circle, and less than radius of circle for
making a more bluff body.
Flow is studied by performing a numerical simulation using commercially available
CFD package called FLUENT. It is found that the variation with Reynolds number
of bluff body characteristics like lift, drag and Strouhal number is similar to that
of a circular cylinder. Critical Reynolds number at which the vortex shedding begins,
is also found to increase with extending shape. As the body is extended to become
more streamlined, lift fluctuations, drag and shedding frequency begin to fall. However,
their variation do not follow a similar pattern for all shape changes. The shape
change is quantified by defining a shape factor.
Variation of the coefficient of lift and Strouhal number is linear with shape factor.
However, the sensitivity of lift force to body shape is dependent on Reynolds number,
while the sensitivity of the Strouhal number is independent of it. Variation of the drag
force on the other hand varies with shape factor according to power law. Using these
relations, lift and drag force, as well as Strouhal number are expressed as functions of
shape factor and Reynolds number. |
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