Investigations on the Trajectory of Large Sandbags in Open Channel Flow
Publication: Journal of Hydraulic Engineering
Volume 138, Issue 12
Abstract
Investigations undertaken to understand the mechanics of the motion of large sandbags and to compute their trajectories are reported in this paper, along with the details of the experimental setup and procedures. The motion of sandbags is recorded from the side of a flume by a high-definition charge-coupled device (CCD) camera, and the digital particle tracking velocimetry (DPTV) technique is used to track the motion of the bags. An equation is developed for the normalized maximum horizontal settling distance from the experimental data. It is found that the particle velocity normal to the flow depends mainly on the characteristic diameter of the particle and the Froude number of the flow, whereas the particle velocity in the streamwise direction shows lower dependency on the Froude number. Analysis of the particle tumbling shows that the Magnus force may be neglected for the purpose of modeling the trajectories of sandbags in uniform flows. A model of particle motion is developed by solving the Lagrangian equation numerically. Two approaches to computing the trajectory of sandbags are investigated. The results show that the approach in which the drag coefficient is varied based on the orientation of a particle gives better results than if the drag coefficient is kept constant and is based on the broadside orientation of the particle. The results also show that the change in the drag coefficient may be as low as 28% to as high as 76% based on the orientation of the particle with respect to the flow.
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Acknowledgments
The authors thank the National Science Foundation for the financial support under Grant No. OISE 0730246. Any opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not reflect the views of the National Science Foundation.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 138 • Issue 12 • December 2012
Pages: 1060 - 1068
Copyright
© 2012 American Society of Civil Engineers.
History
Received: Jul 5, 2011
Accepted: Apr 24, 2012
Published online: Apr 26, 2012
Published in print: Dec 1, 2012
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