1、 ISO 2015 Estimation of sediment deposition in reservoir using one dimensional simulation models Estimation du dpt de sdiments dans le rservoir en utilisant des modles de simulation une dimension TECHNICAL REPORT ISO/TR 11651 Reference number ISO/TR 11651:2015(E) First edition 2015-08-15 ISO/TR 1165
2、1:2015(E)ii ISO 2015 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2015, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
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4、11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO/TR 11651:2015(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 Definitions . 2 4 Units of measurement . 2 5 Principles of quasi-unsteady sediment modelling 2 6 Principles of unst ead y flo w models 2 6.1 General . 2 6.2 Gove
5、rning equations 3 6.3 Numerical techniques for solution of governing equations . 6 6.3.1 Explicit finite-difference methods 7 6.3.2 Implicit finite-difference methods 7 6.3.3 Finite element methods . 7 6.3.4 Finite volume methods . 8 6.4 Sediment transport . 8 7 Data requirements 10 7.1 Selection of
6、 model boundaries .12 7.2 Cross-section data .12 7.2.1 General.12 7.2.2 Mannings n values 13 7.2.3 Movable bed and dredging .13 7.3 Stage data13 7.4 Velocity data .13 7.5 Discharge data 13 7.6 Lateral inflows and withdrawals 14 7.7 Sediment data . 14 8 Formulation, calibration, testing and validatio
7、n of models .15 8.1 Formulation of numerical models .15 8.1.1 Hydrology 15 8.1.2 Geometry .16 8.1.3 Selection of transport equation .16 8.1.4 Bed mixing and armoring algorithm .16 8.2 Preliminary tests 16 8.3 Computational grid and time step.17 8.4 Convergence testing 18 8.5 Boundary and initial con
8、ditions .18 8.6 Calibration .18 8.7 Validation 19 8.8 Predictive simulation 20 8.9 Sensitivity testing 20 8.10 Specific models 20 9 Uncertainties .21 9.1 Model parameters .21 9.2 Data for model development, testing and application .21 9.3 Governing equations .22 9.4 Numerical approximations to gover
9、ning equations 22 Annex A (normative) Models and case studies .24 Bibliography .25 ISO 2015 All rights reserved iii Contents Page ISO/TR 11651:2015(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The wor
10、k of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governme
11、ntal, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in th
12、e ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the poss
13、ibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list o
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15、s information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information The committee responsible for this document is ISO/TC 113, Hydrometry, Subcommittee SC 6, Sediment transport.iv ISO 2015 All rights reserved I
16、SO/TR 11651:2015(E) Introduction Storage reservoirs built across rivers or streams lose their capacity on account of deposition of sediment. Surveys indicate that world-wide reservoirs are losing their storage capacity, at an annual rate of about one percent, due to accumulation of sediments. The im
17、pacts of sedimentation on the performance of the reservoir project are manifold. Some of the important aspects are the following: a) reduction in live storage capacity of the reservoir; b) accumulation of sediment at or near the dam may interfere with the functioning of water intakes and hence is an
18、 important parameter in deciding the location and level of various outlets; c) increased inflow of sediment into the water conveyance systems and hence to be considered in the design of water conductor systems, desilting basins, turbines, etc; d) sediment deposition in the head reaches may cause ris
19、e in flood levels; e) the location and quantity of sediment deposition affects the performance of the sediment sluicing and flushing measures used to restore the storage capacity. Hence, prediction of sediment distribution in reservoirs is essential in the following: a) feasibility studies during pl
20、anning and design of various components of new projects; b) performance assessment of existing projects. The most simple and earliest models to predict the sedimentation processes in reservoirs are the empirical ones. The trap-efficiency curves derived from records of existing reservoirs are among t
21、he most commonly used empirical methods. Recently, due to better understanding of the fundamentals of reservoir hydraulics and morphology, along with the rapid growth of computational facilities, development and application of mathematical models have become a normal practice. Compared to empirical
22、methods, the mathematical approach of the sediment distribution enables more time and space dependent and more accurate modelling. A large number of mathematical models have been developed during the past few decades. Flow in the reservoir can be represented by the basic equations for conservation o
23、f momentum and mass of water and sediment. ISO 2015 All rights reserved v Estimation of sediment deposition in reservoir using one dimensional simulation models 1 Scope This Technical Report describes a method for estimation/prediction of sediment deposition within and upstream of a reservoir using
24、numerical simulation techniques through one-dimensional flow and sediment transport equations. Numerical simulation models for predicting sediment distribution are applicable for reservoirs, where the length of the reservoir greatly exceeds the depth and width and the reservoir has a significant thr
25、ough flow. This Technical Report includes the theoretical basis and fundamental assumptions of the technique and provides a summary of some numerical methods used to solve the unsteady flow and sediment transport equations. Also provided are details on the application of the model, including data re
26、quirements, procedures for model calibration, validation, testing, applications and identification of uncertainties associated with the method. This Technical Report does not provide sufficient information for the development of a computer program for solving the equations, but rather is based on th
27、e assumption that an adequately documented computer program is available. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated refe
28、rences, the latest edition of the referenced document (including any amendments) applies. ISO 748, Hydrometry Measurement of liquid flow in open channels using current-meters or floats ISO 772, Hydrometry Vocabulary and symbols ISO 1100-2, Hydrometry Measurement of liquid flow in open channels Part
29、2: Determination of the stage-discharge relationship ISO 2425, Hydrometry Measurement of liquid flow in open channels under tidal conditions ISO 2537, Hydrometry Rotating-element current-meters ISO 3454, Hydrometry Direct depth sounding and suspension equipment ISO 4363, Measurement of liquid flow i
30、n open channels Methods for measurement of characteristics of suspended sediment ISO 4364, Measurement of liquid flow in open channels Bed material sampling ISO 4365, Liquid flow in open channels Sediment in streams and canals Determination of concentration, particle size distribution and relative d
31、ensity ISO 4373, Hydrometry Water level measuring devices ISO 6416, Hydrometry Measurement of discharge by the ultrasonic (acoustic) method ISO 18365, Hydrometry Selection, establishment and operation of a gauging station ISO/TS 3716, Hydrometry Functional requirements and characteristics of suspend
32、ed-sediment samplers ISO/TR 9212, Methods of measurement of bedload discharge TECHNICAL REPORT ISO/TR 11651:2015(E) ISO 2015 All rights reserved 1 ISO/TR 11651:2015(E) 3 De finiti ons For the purposes of this document, the terms and definitions given in ISO 772 apply. 4 Units of measurement The unit
33、s of measurement used in this Technical Report are SI units. 5 Principles of quasi-unsteady sediment modelling Many early and contemporary sediment models simplify hydrodynamics of sediment transport models by invoking a “quasi-unsteady” flow assumption. Instead of solving the Saint-Venant equations
34、 explicitly or implicitly, the hydrodynamics are represented by a series of steady flow backwater computations and associated with temporal durations. Most generalized sediment transport models still utilize this approach. Because sediment transport and hydraulic processes respond on different time
35、and distance scales and because of the inherent uncertainties associated with sediment simulations, the simplification provided by this approximation often justify the error introduced. However, because the quasi-unsteady approach does not route water, it can be difficult to implement for reservoir
36、modelling. Quasi-unsteady models have been used successfully to model reservoir sedimentation but they require external hydrologic routing computations to define reservoir stage. This process often has to be iterative because the hydrologic routing parameters change in time as the capacity of the re
37、servoir changes with sediment deposition. Therefore, an unsteady approach can be advantageous. 6 Principles of unst ead y flo w models 6.1 General Numerical models are used to solve sedimentation problems in river engineering, especially for long- term simulation of long river reaches. The modelling
38、 cycle is schematically represented in Figure 1. The prototype is the reality to be studied and is defined by data and by knowledge. The data represents boundary conditions, such as bathymetry, water discharges, sediment particle size distributions, vegetation types, etc. The knowledge contains the
39、physical processes that are known to determine the systems behaviour, such as flow turbulence, sediment transport mechanisms and mixing processes. Understanding the prototype and data constitute the first step of the cycle. Mathematicalmodel Numericalmodel Results of modeling Prototype Interpretatio
40、n Solution Interpretation Solution Figure 1 Modelling cycle In the first interpretation step, all the relevant physical processes that were identified in the prototype are translated into governing equations that are compiled into the mathematical model.2 ISO 2015 All rights reserved ISO/TR 11651:20
41、15(E) A mathematical model therefore constitutes the first approximation to the problem. It is the prerequisite for a numerical model. At this time, many simplifying approximations are made, such as steady versus unsteady and one- versus two- versus three-dimensional formulations, simplifying descri
42、ptions of turbulence, etc. In water resources, one usually (but not always) arrives to the set-up of a boundary value problem whose governing equations contain partial differential equations and nonlinear terms. Next, a solution step is required to solve the mathematical model. The numerical model e
43、mbodies the numerical techniques used to solve the set of governing equations that forms the mathematical model. In this step, one chooses, for example, finite difference versus finite element versus finite volume discretization techniques and selects the approach to deal with the nonlinear terms. T
44、his is a further approximating step because the partial differential equations are transformed into algebraic equations, which are approximate but not equivalent to the former. Another solution step involves the solution of the numerical model in a computer and provides the results of modelling. Thi
45、s step embodies further approximations and simplifications, such as those associated with unknown boundary conditions, imprecise bathymetry, unknown water and or sediment discharges and friction factors. Finally, the data needs to be interpreted and placed in the appropriate prototype context. This
46、last step closes the modelling cycle and ultimately provides the answer to the problem that drives the modelling efforts. The choice of model for each specific problem should take into account the requirements of the problem, the knowledge of the system, and the available data. On one hand, the mode
47、l must take into account all the significant phenomena that are known to occur in the system and that will influence the aspects that are being studied. On the other hand, model complexity is limited by the available data. There is no universal model that can be applied to every problem. The specifi
48、c requirements of each problem should be analysed and the model chosen should reflect this analysis in its features and complexity. 6.2 Governing equations The governing equations are the one-dimensional, cross-sectionally averaged expressions for (1) the conservation of mass (or equation of continu
49、ity), (2) conservation of linear momentum and (3) continuity of the bed material. The following one-dimensional flow equations are solved to get the hydraulic parameters such as energy slope, velocity and depth of flow at each cross-section at each time step. The sediment transport capacities at each cross-section are then computed and compared with the sediment inflow. The scour or deposition at each section is computed using sediment continuity equation and new cross-section bed levels are determined accordingly. The com
