| Summary: | 碩士 === 國立成功大學 === 工程科學系 === 86 === Abstract Experiments were performed to study flow structures
behind taoeredcircular cylinders and discontinuous square
cylinders.Five taperedcylinders were used,with taper ratios
varying from 16.1 to 37.1.Foursquare cylinders of two-step and
one of three-step with different arearatios,and one linearly
tapered square cylinder with a taper ratio of 10were studied.
Experiments were conducted both in the water table flow
visualization facility and the wind tunnel facility.The Reynolds
numberfor the former is about 528 and about 7900 for the latter.
From the flow visualization in the water table,the results
indicate thatfor the smaller taper ratio tapered circular
cylinders the formation lengthis longer and the shedding
frequencies have a jump in the middle of themodels.The Strouhal
numbers measured by flow visualization in water tableare higher
than they are measured by hot wire in wind tunnel.It is because
the models in water tabel are higher than the water level and no
free endeffects present which are different from wind tunnel
models.After adding end plate at the top of the models in the
wind tunnel to reduce the three-dimensional free end effects
the shedding frwquency distributionsbecome wider and have higher
values. Because of the sharp-edge geometry of the models,the
square cylinders have about the same Strohal numbers measured
along the height of the modelsboth in the water tabel and in the
wind tunnel.
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