Reply to discussions by E.F.R. Bollaert and A.J. Schleiss on “Jet impact geometry and plunge pool dimensions effects on dynamic pressures at pool sidewalls”Appear in the Canadian Journal of Civil Engineering, 35(11): 1347–1350.

Abstract

The authors appreciate the interesting comments by the discussers. As mentioned in the paper and emphasized by the discussers, low jet velocity cannot show high frequencies above 20 Hz, which occur in the prototype case. Therefore, a scale-up factor would be needed to use the present results for a prototype situation. However, as the present results are the first of their kind, more experimental and prototype results would be needed for a precise scale-up factor. The problem of the air–water mixture at an impact point in high-speed jets and its effect on pressure variation at floor joints is correctly pointed out and discussed by Dr. Bollaert and Professor Schliess in their published papers mentioned in their discussions. Again, the conditions in which air in water has the same effect on the sidewalls as on the pool bottom requires more study. However, this study was intended to show the effect of width dimensions on the sidewall pressure under laboratory conditions. The location of the dynamic pressure measurements in our tests was 10 cm from the bottom, or 1.5 to 3 times the jet width, with more than half of these being less than 2 times the jet width [as suggested by Toso and Bowers (1988)]. As mentioned in the paper, the first series of tests was for the pressure variations on the pool bottom to confirm that the results were compatible with the previous works. The results show that the trend of pressure variations on the plunge floor are acceptable and the differences in peaks are mainly because of the low jet velocities, which in our case is comparable to a high velocity in previous works. Therefore, the authors are confident about the presented results for walls within the test limits as explained in the paper. Another important point with respect to pressure transducer records is the vibration of the apparatus, as correctly pointed out by Professor Schliess. For the presented tests, the Plexiglas plunge pool had metal bracing to minimize vibrations, although no tests were done directly to examine this effect. However, no unusual pressure record was noticed. For higher velocities with a larger impact force to the pool, the possibility of this kind of vibration is probably higher. A test time of 2 min is suggested by many investigators, such as Ervine et al. (1997). Also, for some tests the authors have checked records of up to 10 min, and the 2 min recorded data was found to be a good representation of the extreme pressures. Again, with a higher jet velocity a longer recording time could possibly give better realistic variations of dynamic pressures. The authors would like to emphasize that the present paper consists of the first published results showing the effect of pool and jet dimensions on plunge pool sidewalls. Also, as mentioned in the paper, these results are strictly for primary estimates or a pilot study and cannot be used for design purposes before more laboratory and prototype data are analyzed.