Experimental investigation of loop rating curve on a small 3D printed laboratory channel

International audienceThe study of flood dynamics is generally complicated because it requires a lot of expensive sensors that might be inoperative when submerged during a flood event. Physical models can be helpful in order to get extra information on flood dynamics, but they are expensive in material, space occupation, and human investment (intervention, maintenance, assistance). The objective of this work is a feasibility study on the possibility of using a small 3D printed model to make hydraulic studies. For this we focus on the reproduction of a complex phenomenon which is the loop rating curve (LRC). In natural rivers or large channels, rating curve is a relation between stage and discharge. Under unsteady flow condition, rating curve may present a hysteresis behavior reflected by a more or less pronounced loop. LRC was historically observed on natural rivers or at large laboratory channels. This study is the first investigation of LRC on a small 3D printed laboratory channel. We measure stage and discharge at the channel outlet and we obtain rating curves as a response to an unsteady discharge hydrograph imposed at the channel inlet. We tested 11 scenarios corresponding to different flow conditions where we varied the following parameters: section control (freefall or weir), channel slope (flat = 0.1% or sharp = 10%), time step of the discharge hydrograph (5 s or 10 s). Our experimental results with a small 3D printed channel are in accordance with experimental observations on large channels or natural rivers, and our experimental rating curves are very well simulated by Jones formula that is classically used on large channels or rivers. These promising results allow the use of 3D printing technique to make small-scale hydraulic models. A further study of the rating curve, but also of other hydraulic characteristics can be considered on more complex geometries and more varied scenarios while paying attention to the scaling (which was not the case in this study). As real scenarios might be considered, this might be of interest from both a pedagogical and an application point of view with a reduced human, material and space occupation cost