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The Effect of Transverse Tube Motion on the Unsteady Fluid Forces in a Normal Triangle Tube Array
Loay Alyaldin, Njuki Mureithi

Last modified: 2018-07-07


Previous research work (Ricciardi et al [1] ) conducted on a normal  triangular tube bundle subjected to two-phase flow in the transverse direction, over a range of void fractions, showed that tubes vibrated with large amplitudes as flow velocity increased. The vibration behavior was found to be strongly dependent on void fraction for this tube array geometry. For void fractions up to 40% classical fluidelastic instability was observed. Near 50%-60% void fraction, fluidelastic instability was preceded what was proposed to be strong flow-periodicity induced vibrations. For high void fractions (>70%), the tube array undergoes apparent fluidelastic instability followed by near complete restabilization at high flow velocities.

The present work investigating the stability behavior of the normal triangular array through a detailed experimental test program to determine the fluidelastic forces for a range of void fractions. The dynamic forces are measured with strain gage mounted on the tubes. The geometry of the array is as the following; The P/D is 1.5, and the tube diameter D is 38 mm. The forces are measured at high velocities and void fractions. The results are compared with those obtained in  the rotated triangular tube bundle. A comprehensive study is carried out in order to have an understanding of the physics of the two-phase flow and its behavior within the normal triangular tube array. The dynamic forces associated with the flow analyzed in detail and stabilization behavior clarified.

1)Ricciardi, G., Pettigrew, M. J., & Mureithi, N. W. (2011). Fluidelastic Instability in a Normal Triangular Tube Bundle Subjected to Air-Water Cross-Flow. Journal of pressure vessel technology, 133(6), 061301.

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