Discussion of "Investigation of Flow Upstream of Orifices" by D. B. Bryant, A. A. Khan and N. M. Aziz, Journal of Hydraulic Engineering, January 1, 2008, Vol. 134, No. 1, pp. 98-104

This discussion raises questions about the new method proposed by the authors in their paper

Modal decomposition of linearized open channel flow

Open channel flow is traditionally modeled as an hyperbolic system of conservation laws, which is an infinite dimensional system with complex dynamics. We consider in this paper an open channel represented by the Saint-Venant equations linearized around a non uniform steady flow regime. We use a frequency domain approach to fully characterize the open channel flow dynamics. The use of the Laplace transform enables us to derive the distributed transfer matrix, linking the boundary inputs to the state of the system. The poles of the system are then computed analytically, and each transfer function is decomposed in a series of eigenfunctions, where the influence of space and time variables can be decoupled. As a result, we can express the time-domain response of the whole canal pool to boundary inputs in terms of discharges. This study is first done in the uniform case, and finally extended to the non uniform case. The solution is studied and illustrated on two different canal pools

Discussion of "Development and Verification of an Analytical Solution for Forecasting Nonlinear Kinematic Flood Waves" by Sergio E. Serrano

Discussion of "Development and Verification of an Analytical Solution for Forecasting Nonlinear Kinematic Flood Waves" by Sergio E. Serrano, Journal of Hydrologic Engineering, Vol. 11, No. 4, July/August 2006, pp. 347-353 , doi 10.1061/(ASCE)1084-0699(2006)11:4(347)

Boundary data reconstruction for open channel networks using modal decomposition

This article presents a method to estimate flow variables for an open channel network governed by first-order, linear hyperbolic partial differential equations and subject to periodic forcing. The selected external boundary conditions of the system are defined as the model input; the flow properties at internal locations, as well as the other external boundary conditions, are defined as the output. A spatially-dependent transfer matrix in the frequency domain is constructed to relate the model input and output. A data reconciliation technique efficiently eliminates the error in the measured data and results in a reconciliated external boundary conditions; subsequently, the flow properties at any location in the system can be accurately evaluated. The applicability and effectiveness of the method is substantiated with a case study of the river flow subject to tidal forcing in the Sacramento-San Joaquin Delta, California. It is shown that the proposed method gives an accurate estimation of the flow properties at any intermediate location within the channel network

A new compact model coupling rainfall-runoff and routing model to support reservoir releases management

The article proposes a model for integrated management of a regulated watershed. In such systems, it is important to take into account not only the discharge released at the reservoir, but also the natural flows due to rainfall. The proposed model incorporates both inputs, and can be refined by considering different numbers of sub-basins corresponding to tributaries of the river. We discuss the parameter identification and show that the validation is improved when the discharge transfer inputs are used in the model. These upstream discharge inputs correspond to reservoir releases in the case of a regulated watershed. The model is tested on data from the Tarn river in South-Western France

H infinity observer for time-delay systems. Application to FDI for irrigation canals

This paper deals with the problem of fault detection and isolation for time-varying delayed systems. It consists to develop a $H_{\infty}$ observer that generates residuals sensitive to some faults and insensitive to others in order to detect and isolate actuator faults which can occur on the regulation gates of an irrigation canal. The observer design uses a simplified approximate model of the Saint-Venant equations and is formulated with delay-dependent Linear Matrix Inequality (LMI). Simulations done with a realistic model of a real canal show the effectiveness of the metho

Automatic tuning of PI controllers for an irrigation canal pool

The paper presents a method to automatically tune decentralized Proportional Integral (PI) controllers for an irrigation canal pool. The Auto Tune Variation (ATV) method is based on a relay experiment, which leads to small amplitude oscillations of the canal pool. The test signal is automatically generated by a relay inserted in the feedback loop. The method automatically estimates the ultimate gain and ultimate frequency of the pool, which can be used to tune P, PI or PID controllers. This method does not require advanced automatic control knowledge and is implemented in SIC software, developed by Cemagref, which also incorporates a SCADA module for real-time control. The ATV method is evaluated by simulations and experiments on a real irrigation canal located in the South of France, for local upstream, local downstream and distant downstream controller tuning

Flatness-based control of open-channel flow in an irrigation canal using SCADA

Open channels are used to distribute water to large irrigated areas. In these systems, ensuring timely water delivery is essential to reduce operational water losses. This article derives a method for open-loop control of open channel flow, based on the Hayami model, a parabolic partial differential equation resulting from a simplification of the Saint-Venant equations. The open-loop control is represented as infinite series using differential flatness. Experimental results show the effectiveness of the approach by applying the open-loop controller to a real irrigation canal located in South of France

Hydraulic mangement of filamentous algae in open-channel networks : case study in Southern France

International audiencePeriphyton constitutes the benthic compartment of aquatic environments such as artificial channels which are specific eco-systems for many reasons. Firstly, they have to fulfill hydraulic performance and water quality objectives. These objectives may be affected by filling problems due to algal developments and sanitary risks linked to toxins secreted by Cyanobacteria. Second, compared to natural streams, artificial channels have a relatively simple geometry and their hydraulic variables are easier to monitor. Also, cross regulators allow the managers to control discharges and water elevations. Periphyton dynamics depend on several factors and hydrodynamic is one of the most crucial one. In this article we analyze an original strategy for algal control currently used in a branch of the Canal de Provence (South of France). The management strategy consists of regular flushes causing increases of the bed shear stress from upstream to downstream and consequently algal filament cutting. This is achieved by increasing the discharge at the upstream end of the branch. We first show that turbidity can be used as an indicator for algal detachment. Then, a detachment model is proposed and coupled with the hydrodynamic simulation of the system. It can be fitted very satisfactorily on the turbidity measurements and can be used to improve the management strategy, such as reducing the discharge released

Estimating canal pool resonance with auto tune variation

The Integrator-Delay (ID) model is commonly used to model canal pools which do not exhibit resonance behavior. Simple step tests are often used to estimate ID model parameters; namely, delay time and backwater surface area. These step tests change the canal inflow at the upstream end of the pool and observe water depth variations at the downstream end. Some knowledge of the canal pool characteristics are needed to determine the amount of flow change and its duration. The Auto Tune Variation (ATV) method is one method for determining the duration of these step tests. Pools that are under backwater over their entire length tend to exhibit oscillations due to resonance waves. Binary-Random-Sequence (BRS) tests have been used to determine the resonance frequency of such pools, where step tests with different durations are used. PBRS tests are difficult to implement in practice and may not provide the resonance frequency. The intent of this paper is to demonstrate on a real canal that the ATV method can determine both the resonance frequency and the resonance peak height for canal pools whose water levels oscillate