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ISSN Druckformat: 1065-3090
ISSN Online: 1940-4336
Indexed in
FLOW THROUGH RECTANGULAR CYLINDER BUNDLES
ABSTRAKT
An experimental study is conducted to investigate flow characteristics in rectangular cylinder bundles placed in staggered and in-lined arrangements. Two sets of cylinder bundles, three-row and multiple-row, are tested. Flow visualization by means of a tracer injection method determines flow patterns, while (he laser Doppler velocimetry is employed to obtain the distributions of velocity vector, vorticity, turbulence intensity, and Reynolds stress. A new physical parameter, named arrangement intersecting angle, is proposed to replace the longitudinal and lateral pitches in describing the geometrical features of cylinder bundles in staggered and in-lined arrangements. Two kinds of vortex, separation and impinging-jet vortices, are identified, and their roles in flow behavior are determined by observing flow through the bundles. Of particular interest is the disclosure of flip-flop phenomena, i.e., oscillations of exit streams from the bundles. It is found that these oscillations originate in the second row and are amplified downstreamwise along the flow. The dimensionless optimum frequency of these oscillations, the Strouhal number, is approximately constant at 0.017−0.03 in the range of the Reynolds numbers tested, 3,000 to 15,000. This is an order of magnitude lower than the oscillations of von Karman vortex street behind a single circular cylinder.
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