1、 ISO 2012 Hydrometry Acoustic Doppler profiler Method and application for measurement of flow in open channels Hydromtrie Profils Doppler acoustiques Mthode et application pour le mesurage du dbit en conduites ouvertes TECHNICAL REPORT ISO/TR 24578 First edition 2012-05-15 Reference number ISO/TR 24
2、578:2012(E) ISO/TR 24578:2012(E) ii ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfil
3、m, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ISO/TR 24578
4、:2012(E) ISO 2012 All rights reserved iii Contents Page Foreword iv 1 Scope 1 2 Normative references . 1 3 Terms and definitions . 1 4 Principles of operation . 3 4.1 General . 3 4.2 Doppler principle applied to moving objects . 4 4.3 Acoustic Doppler operating techniques . 6 4.4 Movement monitoring
5、 techniques 12 5 Principles of methods of measurement 13 5.1 Data retrieval modes .13 5.2 Maintenance 13 5.3 Training 13 5.4 Flow determination using a vertically mounted ADCP .13 5.5 Discharge measurement process .16 5.6 Section-by-section method .26 5.7 Ancillary equipment 26 6 Site selection for
6、the use of vertically mounted ADCPs .27 6.1 General .27 6.2 Additional site-selection criteria .27 7 Computation of measurement .28 7.1 Vertically mounted ADCPs 28 7.2 Measurement review .29 8 Uncertainty 30 8.1 General .30 8.2 Definition of uncertainty 30 8.3 Uncertainties in ADCP measurements . Ge
7、neral considerations .31 8.4 Sources of uncertainty .31 8.5 Minimizing uncertainties .32 Annex A (informative) Velocity distribution theory and the extrapolation of velocity profiles 33 Annex B (informative) Determination of discharge between banks and the area of measured discharge .35 Annex C (inf
8、ormative) Example of an equipment check list .38 Annex D (informative) Example of ADCP gauging field sheets 39 Annex E (informative) Beam alignment test 42 Bibliography .44 ISO/TR 24578:2012(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national st
9、andards bodies (ISO member bodies). The work 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 o
10、rganizations, governmental and non-governmental, 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. International Standards are drafted in accordance with the rules giv
11、en in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least
12、75 % of the member bodies casting a vote. In exceptional circumstances, when a technical committee has collected data of a different kind from that which is normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating
13、 members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides are considered to be no longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject
14、 of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 24578 was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommittee SC 1, Velocity area methods. iv ISO 2012 All rights reserved TECHNICAL REPORT ISO/TR 24578:2012(E) Hydrometry Acou
15、stic Doppler profiler Method and application for measurement of flow in open channels 1 Scope This Technical Report deals with the use of boat-mounted acoustic Doppler current profilers (ADCPs) for determining flow in open channels without ice cover. It describes a number of methods of deploying ADC
16、Ps to determine flow. Although, in some cases, these measurements are intended to determine the stage-discharge relationship of a gauging station, this Technical Report deals only with single determination of discharge. The term ADCP has been adopted as a generic term for a technology that is manufa
17、ctured by various companies worldwide. They are also called acoustic Doppler velocity profilers (ADVPs) or acoustic Doppler profilers (ADPs). ADCPs can be used to measure a variety of parameters, such as current or stream flow, water velocity fields, channel bathymetry and estimation of sediment con
18、centration from acoustic backscatter. This Technical Report is generic in form and contains no operational details specific to particular ADCP makes and models. Accordingly, to use this document effectively, it is essential that users are familiar with the terminology and functions of their own ADCP
19、 equipment. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 772, Hydro
20、metry Vocabulary and symbols 3 Terms and definitions For the purpose of this document, the terms and definitions given in ISO 772 and the following apply 3.1 ADCP depth transducer depth depth of the ADCP transducers below the water surface during deployment measured from the centre point of the tran
21、sducer to the water surface NOTE The ADCP depth may be measured either manually or by using an automatic pressure transducer. 3.2 bin depth cell truncated cone-shaped volume of water at a known distance and orientation from the transducers NOTE The ADCP determines an estimated velocity for each cell
22、 using a weighted averaging scheme, which takes account of the water not only in the bin itself but also in the two adjacent bins. 3.3 blank blanking distance distance travelled by the signal when the vibration of the transducer during transmission prevents the transducer from receiving echoes or re
23、turn signals NOTE 1 This is the distance immediately below the ACDP transducers in which no measurement is taken. ISO 2012 All rights reserved 1 ISO/TR 24578:2012(E) NOTE 2 The distance should be the minimum possible. However, care must be taken not to make the distance too short in order to avoid c
24、ontamination by ringing or bias by flow disturbance. 3.4 bottom tracking method whereby the velocity of the bottom is measured together with the water velocity, allowing the system to correct for the movement of the vessel NOTE This acoustic method is used to measure boat speed and direction by comp
25、uting the Doppler shift of sound reflected from the stream bed relative to the ADCP. 3.5 data retrieval modes real-time mode in which the ADCP can retrieve data NOTE A self-contained mode can be used but is not normally recommended. 3.6 deploy ADCP initialized to collect data and propel the instrume
26、nt across the section to record data NOTE A deployment typically includes several (pairs) of transects or traverses across a river or estuary. 3.7 deployment method operating mode technique to propel the ADCP across a watercourse NOTE Three different deployment methods are used: a manned boat; a tet
27、hered boat; or a remote-controlled boat. 3.8 ensemble profile collection of pings NOTE 1 A column of bins equivalent to a vertical (in conventional current meter gauging). NOTE 2 An ensemble or profile may refer to a single measurement of the water column or an average of pings or profile measuremen
28、ts. 3.9 ping series of acoustic pulses, of a given frequency, transmitted by an acoustic Doppler current profiler NOTE Sound pulses transmitted by the ADCP for a single measurement. 3.10 profiling mode ADCP settings for type pattern of sound pulses NOTE 1 Some types of equipment allow settings to be
29、 selected by the user. NOTE 2 Different modes are suitable for different flow regimes, e.g. fast or slow, deep or shallow. 3.11 real-time mode data retrieval mode in which the ADCP relays information to the operating computer as it gathers it. NOTE The ADCP and computer are connected (physically or
30、wireless) throughout the deployment. 2 ISO 2012 All rights reserved ISO/TR 24578:2012(E) 3.12 self-contained mode autonomous mode data retrieval mode in which the ADCP stores the information it gathers within its own memory and then downloaded to a computer after deployment. NOTE This method is gene
31、rally not used by majority of ADCP practitioners nor recommended by the majority of hydrometric practitioners. 3.13 transect pass one sweep across the watercourse during an ADCP deployment NOTE 1 In the self-contained mode, a deployment can consist of any number of transects. NOTE 2 In the real-time
32、 mode, a deployment consists of one transect. 4 Principles of operation 4.1 General The Acoustic Doppler Current Profiler (ADCP) is a device for measuring current velocity and direction, throughout the water column, in an efficient and non-intrusive manner. It can produce an instantaneous velocity p
33、rofile down through the water column while disturbing only the top few decimetres. ADCPs nominally work using the Doppler principle (see 4.2). An ADCP is usually a cylinder with a transducer head on the end (see Figure 1). The transducer head is a ring of three or four acoustic transducers with thei
34、r faces angled to the horizontal and at specified angles to each other. Key 1 forward 2 port 3 starboard 4 aft Figure 1 Sketch illustrating typical ADCP with four sensors ISO 2012 All rights reserved 3 ISO/TR 24578:2012(E) The instrument was originally developed for use in the study of ocean current
35、s tracking them and producing velocity profiles and other oceanographic work. It has since been developed for use in estuaries and rivers. An ADCP can be mounted on a boat or a flotation collar or raft and propelled across a river (see Figure 2). The route taken does not need to be straight or perpe
36、ndicular to the bank. The instrument collects measurements of velocity, depth and position as it goes. The ADCP can also be used to take measurements in fixed positions across the measurement cross section. These fixed positions are similar to verticals in conventional current meter gauging (see ISO
37、 748). This is referred to as the “section-by-section method” (see 5.6). 3 2 4 1 5 Key 1 start 2 path of boat 3 path of boat on river bottom 4 flow velocity vectors 5 finish Figure 2 Sketch illustrating moving-boat ADCP deployment principles 4.2 Doppler principle applied to moving objects The ADCP u
38、ses ultrasound to measure water velocity using a principle of physics discovered by Christian Doppler. The reflection of sound-waves from a moving particle causes an apparent change in frequency to the reflected sound wave. The difference in frequency between the transmitted and reflected sound wave
39、 is known as the Doppler shift. 4 ISO 2012 All rights reserved ISO/TR 24578:2012(E) It should be noted that only components of velocity parallel to the direction of the sound wave produce a Doppler shift. Thus, particles moving at right angles to the direction of the sound waves (i.e. with no veloci
40、ty components in the direction of the sound wave) will not produce a Doppler shift. Figure 3 Reflection of sound-waves by a moving particle results in an apparent change in the frequency of those sound waves Dopplers principle relates the change in frequency to the relative velocities of the source
41、(reflector) and the observer. In the case of most ADCPs, the transmitted sound is reflected off particulates or air bubbles in the water column and reflected back to the transducer. It is assumed that the particulates move at the same velocity as the water and from this the frequency shift can be tr
42、anslated to a velocity magnitude and direction. It should be noted, however, that excessive air bubbles can cause distortion in, or loss of, the returned signal. Furthermore, air bubbles naturally rise and therefore are likely not to be travelling in a representative magnitude and direction. 4.2.1 S
43、peed of sound in water The calculated velocity is directly related to the speed of sound in the water. The speed of sound varies significantly with changes in pressure, water temperature, salinity and sediment concentration, but is most sensitive to changes water temperature. Most manufacturers of A
44、DCP systems measure water temperature near the transducer faces and apply correction factors to allow for temperature related differences in the speed of sound. ADCPs that do not have temperature compensation facilities should be avoided. If the instrument is to be used in waters of varying salinity
45、, the software used to collect data should have the facility to correct for salinity. Figure 4 Sound speed as a function of temperature at different salinity levels (left panel) and salinity at different temperature levels (right panel) ISO 2012 All rights reserved 5 ISO/TR 24578:2012(E) Figure 4 in
46、dicates the effect of temperature and salinity on the speed of sound. As a general rule, a temperature change of 5 C results in a sound speed change of 1 %, a salinity change of 12 ppt (parts per thousand) results in a change in sound speed of 1 %; freshwater is 0 ppt and seawater is in the region o
47、f 30 to 35 ppt), and the full range of typical temperature and salinity levels (2 to 40 C and 0 to 40 ppt) gives a sound speed range of 1 400 to 1 570 m/s (total change of 11 %). 4.3 Acoustic Doppler operating techniques 4.3.1 General All ADCPs fit into one of three general categories, based upon th
48、e method by which the Doppler measurements are made: pulse incoherent (including narrowband); pulse-to-pulse coherent; spread spectrum or broadband. Reference should be made to the instrument manual to determine the type of instrument being used. 4.3.2 Pulse incoherent An incoherent Doppler transmit
49、s a single, relatively long, pulse of sound and measures the Doppler shift, which is used to calculate the velocity of the particles along the path of the acoustic beam. The velocity measurements made using incoherent processing are very robust over a large velocity range, although they have a relatively high short-term (single ping) uncertainty. To reduce the uncertainty, multiple pulses are transmitted over a short time period (typically 9 to 20 per second), these are then averaged before reporting a velocity
