Journal of Flow Visualization and Image Processing

ISSN for PRINT: 1065-3090

For Online Access

Best Paper Award Selection - Editorial Board Site

2001, Volume8

Issue 2-3

110 pages

Issue price - $280.00

Shinzaburo Umeda
Department of Architecture and Civil Engineering, Fukuyama University, Gakuen-cho, Fukuyama, Hiroshima, 729-0292, Japan

The author discovered that a separation bubble, generated at the downstream half of each diamond-shaped column, migrated back and forth from one side (left wall) to the other (right wall) because of the Coanda effect. This causes a periodic alternation in the direction of the downward flow stream in the succeeding bifurcation branches, a phenomenon called flip-flop in the sequencing process influidics. The vortices undergo a chain oscillation that results in the occurrence of flip-flop phenomena in the exiting jet flow. An experimental study was performed to investigate X-shaped intersecting flows in multiple diamond-shaped islands. The upstream and downstream apex angle in islands was 30°. The X-shaped flows in intersecting regions were visualized using the fluorescent dye illuminated by a laser light sheet. The velocity variations in their flow fields were measured using two-dimensional laser Doppler veloci-metry (LDV). It is found that the differences in flow patterns depend on the arrangement of the diamond-shaped islands, the Reynolds number, the existence of the turbulence mesh, and row numbers of diamond-shaped islands. This study also clarified the characteristics of velocity variations in the X-shaped intersecting flows in each intersecting region of diamond-shaped islands. The frequency of alternating flow directions is made dimensionless as the Strouhal number, which is correlated against the Reynolds number with the intersecting angle as the parameter. The mechanisms that cause the reciprocating bubble migration in network ducts of diamond-shaped cylinders are explained.

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