Measurement of liquid flow in open channels — Computing stream flow using an unsteady flow model
Mesure de débit de liquides dans les canaux découverts — Calcul de l'écoulement dans un cours d'eau à l'aide d'un modèle d'écoulement non permanent
Standards Content (sample)
Measurement of liquid flow in open
channels — Computing stream flow using
an unsteady flow model
Mesure de débit de liquides dans les canaux découverts — Calcul de
l'écoulement dans un cours d'eau à l'aide d'un modèle d'écoulement non
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ISO/TR 11627, which is a Technical Report of type 2, was prepared by
Technical Committee ISO/TC 113, Hydrometric determinations, Subcom-
mittee SC 1, Velocity area methods.
This document is being issued in the Technical Report (type 2) series of
publications (according to subclause G.3.2.2 of part 1 of the ISO/IEC
Directives) as a “prospective standard for provisional application” in the
field of hydrometric determinations because there is an urgent need for
© ISO 1998
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ISO ISO/TR 11627:1998(E)
guidance on how standards in this field should be used to meet an ident-
This document is not to be regarded as an “International Standard”. It is
proposed for provisional application so that information and experience of
its use in practice may be gathered. Comments on the content of this
document should be sent to the ISO Central Secretariat.
A review of this Technical Report (type 2) will be carried out not later than
three years after its publication with the options of: extension for another
three years; conversion into an International Standard; or withdrawal.
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TECHNICAL REPORT ISO ISO/TR 11627:1998(E)
Measurement of liquid flow in open channels — Computing stream
flow using an unsteady flow model
This Technical Report describes a method for computing continuous records of stream flow in an
open channel through the numerical solution of the one-dimensional unsteady flow equations. Such
an approach is typically identified as an unsteady flow model and generally involves the use ofcomputers for solution of the flow equations.
Unsteady flow models are appropriate for computing stream flow records at locations where (1) a
single-valued stage-discharge relation does not exist, (2) backwater affects the discharge under
selected or all conditions, (3) flows are affected by tides, or (4) it is not possible to gage the flow using
velocity-area methods. Unsteady flow models also are appropriate for evaluating the effects of changes
in a managed flow regime on downstream conditions prior to the implementation of any changes.
This Technical Report is applicable to steady and unsteady flows, to nominee flows, and to tidal
flows in which there are no significant longitudinal and vertical density gradients. The method is
considered equivalent to, or better than, the commonly used stage-fall-discharge technique
(ISO 1100-1:1996, 7.2 and Annex C) because the method uses information on the physical
characteristics of the channel, including the cross-sectional geometry, channel rugosity and channel
slope, and the method is based on a mathematical description of the physics of fluid flow.
This Technical Report describes the theoretical basis and fundamental assumptions of the technique,
and provides a summary of selected numerical methods used to solve the unsteady flow equations.
Also provided are details on the application of an unsteady flow model, including data requirements,procedures for model calibration, testing, and appli