Abstract
The mechanical properties of flow are very complex in channel arcs. Therefore, dynamic numerical models of fluids are considered effective tools in predicting such flow fields. In this study, the numerical model was validated by the measures of a uniform U-shaped arc with a width of 0.6 meter. Then two similar U shaped arcs, divergent and convergent, were simulated by a three-dimensional numerical model with variable widths from 0.6 to 0.75 meters and 0.6 to 0.45 meters. Validating the numerical model by measured data in the uniform 180-degree arc showed that the model can simulate the flow field in the uniform arc very well. Results regarding several parameters such as rout of maximum velocity, maximum velocity line, water level variations, power of spiral flow, existence of a rotating cell are stated and discussed.
Highlights
Simulation of flow patterns is the most interesting subject in river engineering and sedimentation studies [1]
It should be noted that in Pirestani’s research, flow velocities were measured at different depths in 91 cross sections along the bend with a two dimensional portable emissions measurement systems (PEMS)
Statistical comparison of the calculated and measured velocities at a plane near the water surface shows that the maximum ERMS and EM are equal to 0.074 m/s and –0.066 m/s, respectively, indicating good agreement between measured and calculated velocities in the uniform bend
Summary
Simulation of flow patterns is the most interesting subject in river engineering and sedimentation studies [1]. In [7], authors exercised the effect of secondary flow on depth-averaged equations by using stress diffusion matrix and studied flow pattern in 1800 bend with rigid bed through their 2-D numerical model. In [10], authors developed a 2-D model to compute the diffusion term in convection equation of suspended sediments, which increase efficiency of 2-D models to simulate the secondary flows in channel bends They studied the over-time bed evolution in 1800 river bends with SSIIM 3-D model [10]. In their research several parameters (e.g., stream wise and vertical velocity profile, bed shear stress distribution, stream wise and span wise slopes of water surface and helical flow strength) were compared in 1800 divergent and uniform bends. Where U* is the shear velocity, U is the velocity at the center of the grid cell closest to the bed, κ is a constant equal to 0.4, y is the distance from the wall to the center of the grid cell, and ks is wall roughness
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