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Direct numerical simulation of turbulent flow over a backward-facing step
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Kopera, Michal Andrzej (2011) Direct numerical simulation of turbulent flow over a backward-facing step. PhD thesis, University of Warwick.
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WRAP_THESIS_Kopera_2011.pdf - Submitted Version Download (60Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b2578305~S1
Abstract
A three-dimensional, turbulent
flow in a channel with a sudden expansion
was studied by direct numerical simulation of the incompressible Navier-Stokes
equations. The objective of this study was to provide statistical data of backwardfacing
step
flow for turbulence modelling. Additionally, analysis of the statistical
and dynamical properties of the
flow is performed.
The Reynolds number of the main simulation was Reh = 9000, based on the
step height and mean inlet velocity, with the expansion ratio ER = 2:0. The discretisation
is performed using the spectral/hp element method with stiffly-stable
velocity correction scheme for time integration. The inlet boundary condition is
a fully turbulent velocity and pressure field regenerated from a plane downstream
of the inlet. A constant
flowrate was ensured by applying Stokes
flow correction
in the inlet regeneration area.
Time and spanwise averaged results revealed, apart from the primary recirculation
bubble, secondary and tertiary corner eddies. Streamlines show an additional
small eddy at the downstream tip of the secondary corner eddy, with the
same circulation direction as the secondary vortex. The analysis of the 3D, timeonly
average shows the wavy spanwise structure of both primary and secondary
recirculation bubble, that results in spanwise variations of the mean reattachment
location. The visualisation of spanwise averaged pressure
uctuations and
streamwise velocity showed that the interaction of vortices with the recirculation
bubble is responsible for the
apping of the reattachment position. The
characteristic frequency St = 0:078 was found.
The analysis of small-scale energy transfer was performed to reveal large
backscatter regions in strong Reynolds stress areas in the mixing layer. High
correlation of small-scale transfer with non-linear interaction of large-scale velocity
and small-scale vorticity was found.
The data of the
flow fields was archived. It contains the averages for velocities,
pressure and Reynolds stress tensor, as well as 3D instantaneous pressure and
velocity history.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QA Mathematics | ||||
Library of Congress Subject Headings (LCSH): | Turbulence -- Mathematical models, Navier-Stokes equations | ||||
Official Date: | March 2011 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Engineering | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Kerr, Robert | ||||
Sponsors: | Engineering and Physical Sciences Research Council (EPSRC) (EP/C007921/1, EP/G069581/1) | ||||
Extent: | x, 158 leaves : ill., charts | ||||
Language: | eng |
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