Numerical Modeling in Physical Model and Sensitivity Analysis of Secondary Currents

A live bed physical model was built to represent a meandering reach of the Madre de Dios river at National Hydraulic Laboratory - LNH, in which the width to depth ratio (R/B) is equal to 2. Velocities were measured with an Acoustic Doppler Velocimeter (ADV), which allows measuring the velocity field in three (3) dimensions. The experimental study were complemented with numerical simulations using open source TELEMAC-2D and SISYPHE to analyze the secondary flow currents that occurs in the curved section.

In curved channel, the problem of lateral migration in rivers is due to the presence of secondary flow in the section of the curved section. The superficial secondary currents, and those that are near the bed, generate the phenomenon of scour in the external bank and sedimentation in the internal bank. This is a phenomenon of three-dimensional nature, where helical flows that begin when water enters the section with canal curvature

The method for secondary currents in TELEMAC-2D have a more accurate representation of secondary flow effects in two dimensional simulations, these two parameters: production coefficient for secondary currents As and dissipation coefficient for secondary currents Ds (7.071 and 0.5 ), this affect the water level and adjustments in roughness should be consider.

In this case, helicoidal flow increases the velocity, depths and shear stresses in the external bank, for this kind of issue both options, with secondary flow correction and without secondary flow correction, because when use shallow water equation, it is not consider vertical velocities for this reason we have a comparisons between both simulations showed that, in this case, it was necessary to include correction by secondary flow to more accurately model flow patterns in cases like this one. Including the secondary flow correction, the final cross section geometries were adequately predicted, particularly near the thalweg, where the maximum depth occurs.