9 research outputs found

    Contribution a l'etude de la chromatographie preparative avec eluant supercritique

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    SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79763 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

    Use of the Hayami diffusive wave equation to model the relationship infected–recoveries–deaths of Covid-19 pandemic

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    International audienceUse of the Hayami diffusive wave equation to model the relationship infected-recoveriesdeaths of Covid-19 pandemic. Epidemiology and Infection 149, e138, 1-13

    Evaluating lateral flow in an experimental channel using the diffusive wave inverse problem

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    International audienceLateral flow L(t) is a major process during flood events, which can be either gains (positive) or losses (negative) to the channel. The inverse problem consists of evaluating L(t) knowing the inflow I(t) and the outflow O(t) on a channel. However L(t) is very difficult to measure on real channels, and we are always not sure to which extent the evaluated L(t) is close to the real one. This paper aims at evaluating L(t) in a channel using the analytical solution of the inverse problem of the Hayami diffusive wave equation (DWE) with L(t) uniformly distributed along the channel. We conceived and built a novel experimental channel where I(t), O(t) and L(t) are highly controlled at 1 s time step and we realize 62 experimental hydrograph scenarios corresponding to different shapes of I(t) and L(t). We validate the hypotheses of both the DWE Hayami model and the corresponding inverse model (with very high criteria functions values for a large majority of scenarios) which reflects the ability of the DWE inverse model to reproduce complex lateral flow hydrograph dynamics. We discuss the limits of application of the DWE especially for short wave lengths. The coupled experimental-modelling approach proposed herein opens promising perspectives regarding the evaluation of lateral flow on real channels

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

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    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

    A New Water Level Measurement Method Combining Infrared Sensors and Floats for Applications on Laboratory Scale Channel under Unsteady Flow Regime

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    In this paper, we studied water transport under an unsteady flow regime in an experimental channel (4 m in length; 3 cm in width). Our experiments implicated some measuring requirements, specifically, a water level (WL) detection technique that is able to measure WL in a range of 2 cm with a precision of 1 mm. The existing WL detection techniques could not meet our measurement requirements. Therefore, we propose a new measurement method that combines two approaches: An “old„ water contact technique (float) with a “new„ remote non-contact technique (infrared sensor). We used an extruded polystyrene (XPS Foam) that needed some adequate treatment before using it as float in experimental measurements. The combination of IR-sensors with treated float foam lead to a sensitive measurement method that is able to detect flat and sharp flow signals, as well as highly dynamic variations of water surface level. Based on the experimental measurements of WL and outflow at the channel output, we deduced a loop rating curve that is suitable with a power law adjustment. The new measurement method could be extended to larger scale applications like rivers and more complicated cross section geometry of irregular shape

    A novel platform to evaluate the dampening of water and solute transport in an experimental channel under unsteady flow conditions

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    International audienceThis paper presents a novel platform to study the dampening of water and solute transport in an experimental channel under unsteady flow conditions, where literature data are scarce. We address the question about what could be the smallest size of experimental platform that is useful for research, project studies, and teaching activities and that allows to do rational experiments characterized by small space occupation, short experimental duration, high measurement precision, high quality and reproducible experimental curves, low water and energy consumption, and the possibility to test a large variety of hydrograph scenarios. Whereas large scale hydraulic laboratories have focused their studies on sediment transport, our platform deals with solute transport. The objectives of our study are (a) building a platform that allows to do rational experiments, (b) enriching the lack of experimental data concerning water and solute transport under unsteady state conditions, and (c) studying the dampening of water and solute transport. We studied solute transport in a channel with lateral gain and lateral loss under different experimental configurations, and we show how the same lateral loss flow event can lead to different lateral loss mass repartitions under different configurations. In order to characterize water and solute dampening between the input and the output of the channel, we calculate dampening ratios based on peak coordinates of time flow curves and time mass curves and that express the decrease of peak amplitude and the increase of peak occurrence time between the input and output curves. Finally, we use a solute transport model coupling the diffusive wave equation for water transfer and the advection-diffusion equation for solute transport in order to simulate the experimental data. The simulations are quite good with a Nash-Sutcliffe efficiency NSE > 0.98 for water transfer and 0.84 < NSE < 0.97 for solute transport. This platform could serve hydrological modellers because it offers a variety of measured parameters (flow, water height, and solute concentration), at a fine time step under unsteady flow conditions