Experimental-numerical study of the velocity field in a rectangular channel with composite curvature and variable width in 2DH

Abstract

An analysis of the approximation obtained with the mathematical modeling systems HEC-RAS, Iber, and Telemac–Mascaret is presented, for calculating the velocity field in a rectangular section channel with compound curvature and variable width. On the channel, secondary currents and flow separation were developed; all three models are free to use and based on the horizontal two-dimensional flow (2DH) hypothesis. The Saint Venant equations are used in each mathematical model to calculate hydrodynamics and turbulence. The velocity field is determined from physical measurements in a laboratory channel with an acoustic Doppler velocimeter (Micro-ADV 16 MHz) and it is compared with the velocity fields calculated with the mathematical modeling systems (HEC-RAS, Iber, and Telemac-Mascaret). An error analysis is presented, with the aim of determining the degree of approximation obtained with each modeling system and of discussing the factors and phenomena observed in the laboratory, this allows to have facts about the complexity and nature of turbulent flows in channels with strong bents. It was found that the three models, in general have similar and acceptable behavior, with an average approximation greater than 93%; on the other hand, in an analysis by section, in a recirculation zone, flow separation and high turbulence were observed (physical processes of fluid dynamics that the models used cannot reproduce adequately), and so the average approximation decreases to 82.5 %.