A self-induced flip-flop flow phenomenon in diamond-shaped cylinder bundles has been disclosed in previous studies by the authors. The flip-flop flow oscillation promotes fluid mixing and thus contributes to an enhancement in convective heat and mass transfer when the cylinder bundles are used as heat and mass exchanger equipment. An experimental study was performed to disclose the occurrence of flip-flop flows in diamond-shaped cylinder bundles. Velocity and pressure fluctuations in

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... low region inside diamond-shaped cylinder bundles were measured by LDV and piezo-meter, respectively. The difference in the oscillations of flip-flop flows and von Karman vortex streets is disclosed quantitatively. The mechanisms that cause the reciprocating bubble migration in network ducts of diamond-shaped cylinders are explained.