• Haoze Fang, Zhonghua Yang, Huilin Wang, and Yujie Fan.
• State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, Hubei, China.
• Environ Sci Pollut Res Int. 2021 Mar 1; 28 (10): 12817-12830.

AbstractThe longitudinal dispersion coefficient is an important index for contaminant transports in rivers. Investigating it by using an analytical approach is conducive to obtain its expression with physical meanings and wide application ranges. However, the analytical solutions are extremely complex for subsequent derivations when many influencing factors, such as benthic vegetation and surface wind, are considered. This study combines turbulent flow theory and Biot's theory for poroelasticity into a two-layer flow model and acquires the analytical solutions of velocity. A database is generated from the analytical solutions to search a more concise expression of velocity through genetic programming. A formula for longitudinal dispersion coefficients of submerged vegetation flow under the effect of surface wind is deduced on the basis of this expression. Calculated coefficients from the formula are compared with the experimental coefficients from the model and real vegetation to show its validity. The formula indicates that the longitudinal dispersion coefficients are mainly affected by turbulent effect, vegetation height, and surface wind. The growth of vegetation height can weaken the influence of surface wind on longitudinal dispersion coefficient.

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