The impact of ice on momentum transfer in rivers of cold regions
North Dakota State University
Abstract
River ice is a common phenomenon in cold regions during winter. Its presence alters hydrodynamics of rivers from the ice boundary to the river bed. In this project, we developed new methodologies to study ice-covered flows in small and medium-sized rivers using Unmanned Aerial Vehicle (UAV), pointwise measurements, and Large Eddy Simulation. First, we developed a theoretical model for the lateral momentum transfer and depth-averaged velocity profiles in ice-covered rivers using the depth-integrated Reynolds-Averaged Navier–Stokes equations. Second, a series of field measurement campaigns (Acoustic Doppler Current Profiler- ADCP and Acoustic Doppler Velocimetry) were conducted to validate our theoretical model in the Red River of the North in Fargo, North Dakota and Buffalo River, Minnesota in United States under fully ice-coverage from 2020 to 2025. Our results show that secondary flows and Reynolds stresses both contribute to the lateral momentum load. Also, the ice cover suppresses the development of coherent secondary cells. A term-by-term analysis of streamwise momentum budget demonstrates that lateral gradients of momentum load are closely tied to variations in bed shear stress, highlighting the coupling between momentum load and near-bed dynamics. Finally, a Large-Eddy Simulation is carried out with inputs from field measurements for the Red River reach. Our results show a significant impact of ice cover in changing the spatial arrangement of the turbulent statistics and the secondary flow structures. Specifically, the Turbulent Kinetic Energy is altered significantly near the bend apex as the result of the interaction between the turbulent jet and the ice cover in regions near both banks. Our results suggest that ice coverage promote the redistribution of momentum and sustain turbulence near banks. Our work reveals a hidden role of ice coverage in moderating the bed shear stresses near river banks in winter. This work proposes a fundamental framework to study river ice dynamics and also provide practical tools for monitoring and predicting flow profiles under ice conditions in rivers of cold regions, which are under pressure of a changing cryosphere globally. This study is supported by National Science Foundation (NSF) CAREER Award No. 2239799.
About the speaker
Dr. Trung Le is an Associate Professor at the Department of Civil, Construction and Environmental Engineering at North Dakota State University, United States. His research interest focuses on computational methods and data analytics for complex flows in bioengineering and environmental problems. He received a number of national and international awards including the Gallery of Fluid Motion (American Physical Society Division of Fluid Dynamics) and National Science Foundation CAREER Award.
