Time-average velocity distribution in steady and uniform channel flows is important for fundamental research and practical application as it is always three-dimensional (3D), regardless of channel geometry. However, its determination has predominantly been carried out by using complex numerical software, even for the simplest geometry such as rectangular channels. The log-law was developed initially for circular pipe flows, where a single shear velocity is used to normalize the velocity (u+) and its distance (y+). Tracy and Lester found that the performance of the log-law can be extended to express velocity profiles in rectangular channels when the global shear velocities (gRS)0.5 and (ghS)0.5 are used to normalize the measured velocity u and its distance y. This study extends this discovery from the channel central line to the corner regions, and its general form of log-law was found to be valid even in trapezoidal or triangular open channels or closed ducts. This modified log-law can produce good agreement with the measured velocity with an average error of less than 5%. Therefore, this study provides a simple and reliable tool for engineers and researchers to estimate the velocity contours in straight and smooth channel flows.
Three-Dimensional Velocity Distribution in Straight Smooth Channels Modeled by Modified Log-Law
Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received October 24, 2018; final manuscript received June 25, 2019; published online July 19, 2019. Assoc. Editor: Devesh Ranjan.
Yang, S., Riaz, M. Z. B., Sivakumar, M., Enever, K., and Miguntanna, N. S. (July 19, 2019). "Three-Dimensional Velocity Distribution in Straight Smooth Channels Modeled by Modified Log-Law." ASME. J. Fluids Eng. January 2020; 142(1): 011401. https://doi.org/10.1115/1.4044183
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