Characteristic curve at the inlet of a culvert-type hydraulic model

Abstract

Introduction: Due to the hypotheses set out in the equations for the design of hydraulic structures, the flow does not follow a real behavior; therefore, it is necessary to build physical and numerical models to obtain adequate results. Objective: To obtain the characteristic curve of the real behavior of the transition zone of a culvert with inlet control, as well as the mathematical models of the hydraulic operation. Methodology: The experiment was carried out in a physical model built and instrumented with two sensors: an HC-SR04 for measuring the water level and an FS400a for the discharge. The inlet discharge was varied with a gate valve to obtain the characteristic curve. By means of least-squares fitting, the mathematical models for the weir, transition, orifice and overall operation zones were obtained. Results: The characteristic curve of the system was fitted to a third degree polynomial. The global model Q = f(H) ranged from 0.066 to 0.286 m, where 25 % of the water surface heights (0.066 < H ≤ 0.117 m) behaved as a weir, 23.53 % (0.117 < H ≤ 0.165 m) as a transition zone and 51.47 % (0.165 < H ≤ 0.286 m) as an orifice, obtaining in all cases an R2 > 0.98. Study limitations: The models obtained can only be scaled in culverts with geometry similar to the physical model studied. Originality: We worked with experimental data and the weir-orifice transition model. Conclusions: The transition zone presented a curved trend, although the linear model, found in the literature, only loses 0.2 % accuracy.