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Large-eddy simulation study of Reynolds number effects on the flow around a wall-mounted hemisphere in a boundary layer
Large-eddy simulations were used to investigate unsteady flows around a wall-mounted hemisphere as the Reynolds number (Re, based on the diameter of the hemisphere D) increased from 7 × 104 to 7 × 105. The hemisphere was immersed in a low-turbulence-intensity boundary layer with a thickness of δ/D =...
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Published in: | Physics of fluids (1994) 2020-02, Vol.32 (2) |
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Main Authors: | , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Large-eddy simulations were used to investigate unsteady flows around a wall-mounted
hemisphere as the Reynolds number (Re, based on the diameter of the hemisphere
D) increased from 7 × 104 to 7 × 105. The
hemisphere was immersed in a low-turbulence-intensity boundary layer with a thickness of
δ/D = 0.5. Strong Re dependence was confirmed to be
present even for the flow around a wall-mounted obstacle after systematic examination of
aerodynamic forces, local pressures, and flow structures. Drag and lift crises were
observed simultaneously, with the critical Re noted at approximately 3 × 105.
As with circular cylinders and spheres, a laminar-turbulent transition and induced flow
separation delay were observed in the supercritical Re regime. Flow separation occurred on
the sides of the body later than on the top, regardless of whether Re was subcritical or
supercritical. The spatial and temporal features of flow structures at different scales
were described in detail based on the present high-resolution simulations. The coexistence
of lateral oscillations and arch-type vortex shedding occurred throughout the subcritical
and supercritical Re range. However, both of these motions diminished in scale and
strength at supercritical Re. Flow motion frequencies were also quantified. The frequency
ratio of arch vortex shedding to lateral oscillation was approximately 4 at subcritical Re
but decreased to 3 at supercritical Re. |
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ISSN: | 1070-6631 1089-7666 |
DOI: | 10.1063/1.5142371 |