Abstract
In this paper, we leverage the direct numerical simulation (DNS) data for closed-channel flow for a range of friction Reynolds number (Reτ∼180-5,000) to develop a new one-point friction velocity method (OPFVM) to calculate friction velocity U∗ in terms of free-surface velocity Um, flow depth h, and kinematic viscosity ν. In contrast to prevalent methods that require several cumbersome near boundary measurements to obtain friction velocity, the OPFVM relies on a single easy-to-measure free-surface velocity measurement. The formulation is used to obtain friction velocity for a closed-channel flow (CCF) DNS regime with Reτ=10,049 and on four open-channel flow (OCF) DNS regimes with Reτ∼180-2,000. The same formulation was then experimentally verified in our laboratory. To avoid being prescriptive, a sensitivity analysis was performed to determine the permissible variation in Um to restrict the error in estimated U∗ to 2%. The relationship between the depth-averaged velocity Ub and the maximum free-stream velocity Um is also explored using the DNS data sets and an approximate relationship between Ub and Um is proposed. With advances in remote-sensing technology that enables free-stream velocity measurements, this method extends the potential to measure even the friction velocity remotely.
Recommended Citation
H. Mishra and S. K. Venayagamoorthy, "New Method to Calculate Friction Velocity in Smooth Channel Flows using Direct Numerical Simulation Data," Journal of Hydraulic Engineering, vol. 150, no. 4, article no. 04024019, American Society of Civil Engineers, Jul 2024.
The definitive version is available at https://doi.org/10.1061/JHEND8.HYENG-13754
Department(s)
Civil, Architectural and Environmental Engineering
International Standard Serial Number (ISSN)
1943-7900; 0733-9429
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2025 American Society of Civil Engineers, All rights reserved.
Publication Date
01 Jul 2024
