Experimental Study on Front Spreading of Lock-Exchange Gravity Current with Long Lock Length
Publication: Journal of Engineering Mechanics
Volume 146, Issue 1
Abstract
Full-depth lock-exchange experiments of saltwater with a lock length of 40 m were conducted in a horizontal open channel in order to gain insight into the gravity currents of long lock releases. Without the effects of backreflected waves and initial volume on their development, the experiments showed that the front spreading distances and front velocities developed very smoothly without any transitions. But they were significantly affected by drag and friction. Their variations with time in later periods were different from the previously published results for gravity flows of small-volume release. The current was analyzed using one-layer open-channel hydraulics. The theoretical results show that the front traveling length over time is a quadratic function and the front velocity decreases linearly based on the initial speed, which is related to the drag coefficient. Similarly, the front height also decreases linearly from half of the total water depth. The rate of the decrease depends on drag and friction, which can be represented by the velocity coefficient at a gate section and the dimensionless Chezy’s coefficient . The resulting expressions reveal the effects of drag and friction on all the current processes in the slumping phase. The theoretical and experimental results are in satisfactory agreement. Comparison of previous and present results indicates that a power law does not fit well all the flow processes of the experiments. It is found that the experiments in a later period are close to the gravity current of constant discharge in the buoyancy-viscous phase.
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Data Availability Statement
Some or all data, models, or code generated or used during the study are available from the corresponding author by request.
Acknowledgments
This research was sponsored by the National Key Research and Development Program of China (2016YFC0402600), the National Natural Science Foundation of China (11572130, 11872117, and 11432015) and the Open Research Foundation of the Key Laboratory of the Pearl River Estuarine Dynamics and Associated Process Regulation, Ministry of Water Resources (2017KJ02). The authors are grateful to the Center for Coastal Ocean Science and Technology, Marine School of Sun Yat-sen University, for helpful discussions.
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Published In
Journal of Engineering Mechanics
Volume 146 • Issue 1 • January 2020
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©2019 American Society of Civil Engineers.
History
Received: Oct 11, 2018
Accepted: May 28, 2019
Published online: Oct 31, 2019
Published in print: Jan 1, 2020
Discussion open until: Mar 31, 2020
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