Shahid Chamran University of AhvazIrrigation Sciences and Engineering2588-595238420160121Calibration of Shiono and Knight Model to Estimate Shear Stress
for Trapezoidal ChannelCalibration of Shiono and Knight Model to Estimate Shear Stress
for Trapezoidal Channel1892011180510.22055/jise.2016.11805FABabakLashkar AraIran DokhtDehghaniJournal Article20140607Aim of this study is to calibrate Shiono and Knight model for better determination of shear and velocity distribution in trapezoidal open channels. To do this, correct estimation of friction factor (<em>f)</em>, secondary current (Γ), and eddy viscosity (λ) is proposed as key affecting parameters. Available data in literature are used to optimize these three parameters. Using channel aspect ratio <em>P<sub>b</sub>/P<sub>w</sub></em>, the channel subsections are selected. Non-dominated Sorting Genetic Algorithm is used to optimize the parameters and estimate shear and velocity distribution for each subsection. Results reveal that effects of friction factor and eddy viscosity are significant for aspect ratios of less than 2 and 6, respectively. Rate of change of the parameters with the aspect ratio show a considerable increase for aspect ratios of less than 4. In oppose to the literature for suggestion of a constant eddy viscosity of 0.67, calibration of the Shiono and Knight model in this study showed a variable eddy viscosity for variable flow conditions. Comparison of the model and experimental results confirms correct estimation of the aforementioned parameters. <br /> Aim of this study is to calibrate Shiono and Knight model for better determination of shear and velocity distribution in trapezoidal open channels. To do this, correct estimation of friction factor (<em>f)</em>, secondary current (Γ), and eddy viscosity (λ) is proposed as key affecting parameters. Available data in literature are used to optimize these three parameters. Using channel aspect ratio <em>P<sub>b</sub>/P<sub>w</sub></em>, the channel subsections are selected. Non-dominated Sorting Genetic Algorithm is used to optimize the parameters and estimate shear and velocity distribution for each subsection. Results reveal that effects of friction factor and eddy viscosity are significant for aspect ratios of less than 2 and 6, respectively. Rate of change of the parameters with the aspect ratio show a considerable increase for aspect ratios of less than 4. In oppose to the literature for suggestion of a constant eddy viscosity of 0.67, calibration of the Shiono and Knight model in this study showed a variable eddy viscosity for variable flow conditions. Comparison of the model and experimental results confirms correct estimation of the aforementioned parameters. <br /> https://jise.scu.ac.ir/article_11805_88daad92a2b85e052f754f7879c66580.pdf