An analysis of the effect of the change of cross-sectional velocity distribution and the change of the number of measurement vertical lines on the accuracy of flow discharge calculation

Kwonkyu Yu; Byungman Yoon; Junhyeong Lee

doi:10.3741/JKWRA.2025.58.3.277

All Issue

2025 Vol.58, Issue 3 Preview Page

Research Article

An analysis of the effect of the change of cross-sectional velocity distribution and the change of the number of measurement vertical lines on the accuracy of flow discharge calculation 하천의 횡단면 유속분포와 측선수 설정이 유량산정 정확도에 미치는 영향 분석

31 March 2025. pp. 277-286

PDF XML

Abstract

Recently, various non-contact flow rate measurement techniques have been developed to enable real-time automatic measurement of river flow discharges. In real-time automatic flow discharge measurements, most of them measure the flow velocities and apply them to the velocity-area method to calculate the flow discharge. In the case of using the velocity-area method in this way, in order to calculate the reliable flow discharge, the regulations on the number of measurement vertical lines (the number of sub-sections of the measuring cross-section) stipulated in ISO 748:2021 must be followed. However, in the recent river discharge measurement project, there have been attempts to not comply with these vertical line regulations due to 'factors outside the technology'. In this paper, we tried to confirm the validity of the existing regulations on the number of vertical lines by using the data measured for the Andong River Experiment Center and the actual small-sized rivers (the Insu Stream, the Baegun Stream). The flow discharge calculated by using the flow velocity distribution measured by 30 vertical lines in the streams was assumed as a reference value, and the error of the calculated flow discharges were analyzed by increasing the number of vertical lines from 1 to 30. As a result, in order to reduce the flow discharge calculation error to within 5~10%, it was found that at least 4~6 vertical lines were required even in very good conditions, at least 7 in actual small-sized streams, and usually at least 10 vertical lines were required. In other words, although regulations of ISO 748:2021 are a little excessive in the reality of Korea's river flow discharge measurement project, they must be observed as much as possible, and even in inevitable cases, efforts need to be made to maintain the number of vertical lines close to them.

Keywords

Flow discharge

Automatic flow discharge measurement

ISO 748:2021

Number of measurement vertical lines

Velocity-area method

Velocity distribution

최근 다양한 비접촉식 유속측정기법이 개발되어 하천 유량의 실시간 자동측정이 가능하게 되었다. 실시간 자동유량 측정에서는 대부분 유속을 측정하고 이를 유속면적법에 적용하여 유량을 산정한다. 이렇게 유속면적법을 이용하는 경우 신뢰성있는 유량을 산정하기 위해서는 ISO 748:2021 등에서 규정한 측선수(측정소단면 수)에 대한 규정을 따라야 한다. 그러나 최근에 진행되는 하천유량 측정 사업에서는 ‘기술 외적인 요인’으로 이런 측선 규정을 준수하지 않으려는 시도가 나타나고 있다. 본고에서는 안동하천실험센터와 실제 소하천(인수천, 백운천)에 대해 측정된 자료를 이용하여 측선수에 대한 기존 규정의 타당성을 확인해 보고자 하였다. 해당 하천에서 측선수 30개로 측정된 유속분포를 이용하여 산정한 유량을 기준값으로 보고, 측선수를 1개부터 30개까지 늘리면서 산정유량의 오차를 분석하였다. 그 결과 유량산정오차를 5~10% 이내로 줄이기 위해서는 아주 좋은 조건의 수로에서도 최소 4~6개, 실제 소하천에서는 최소 7개 이상, 보통은 10여개 이상의 측선수를 필요로 하는 것을 알았다. 즉, ISO 748:2021의 규정이 우리나라의 하천유량측정사업의 현실에서는 조금 과하기는 하지만, 가급적 준수해야 하고, 불가피한 경우라도 이에 가까운 측선수를 유지하고자 노력할 필요가 있다.

키워드

유량

자동유량측정

ISO 748:2021

측선수

유속면적법

유속분포

References

Carter, R.W., and Anderson, I.E. (1963). "Accuracy of current meter measurements." Journal of Hydraulics Division, Proceedings of the American Society of Civil Engineers, Vol. 8, No. HY4, Part 1, pp. 105-115.

10.1061/JYCEAJ.0000898

Herschy, R.W. (1975). "The accuracy of current meter measurements." Proceedings, Institution of Civil Engineers (Great Britain), Part 2, Vol. 65, pp. 431-437.

10.1680/iicep.1978.2955

HydroSEM (2024). User's manual, RiverQ_ML v.3.0.

Industrial Standard Council (ISC) (2021) Hydrometry - Measurement of liquid flow in open channels - velocity area method using point velocity measurement. KS B ISO 748:2007.

Industrial Standard Council (ISC) (2024) Hydrometry - Measurement of liquid flow in open channels - velocity area method using point velocity measurement. KS B ISO 748:2021.

International Standard Organization (ISO) (1979). Hydrometru - Measurement of liquid flow in open channels - velocity area method using point velocity measurement. ISO 748:1979, Geneva, Swiss.

International Standard Organization (ISO) (2007). Hydrometru - Measurement of liquid flow in open channels - velocity area method using point velocity measurement. ISO 748:2007, Geneva, Swiss.

International Standard Organization (ISO) (2021). Hydrometru - Measurement of liquid flow in open channels - velocity area method using point velocity measurement. ISO 748:2021, Geneva, Swiss.

Kim, C.Y., Cha, J.H., Kim, D.G., and Kim, W. (2004). "Uncertainties due to the limited number of verticals in river discharge measurement." Proceedings of 2024 Korean Water Resources Association Conference, pp. 1086-1091.

Korea Institute of Construction Technology (KICT) (2024). 2024 Small river smart measurement management project performance verification experiment project, KICT General Project 2024-019.

Korea Institute of Hydrological Survey (KIHS) (2022). Flow measurement manual.

Korean Water Resource Association (KWRA) (2019). Explanation of river design standards.

Lee, Y., and Yu, K. (2023) "Development of a practical surface image velocimeter using spatio-temporal images." Ecology and Resilient Infrastructure, Vol. 10, No. 4, pp. 208-216.

Ministry of Land, Infrastructure, Transport and Tourism (MLIT) (2023). Guide to non-contact flow velocity measurement method (proposal). Tokyo, Japan.

Pelletier, P.M. (1988). "Uncertainties in the single determination of river discharge: A literature review." Canadian Journal of Civil Engineering, Vol. 15, pp. 834-850.

10.1139/l88-109

Suzuki, M., Takahashi, K., and Usuda, C. (2020). "Measurement line setting in high water flow observation - accuracy verification for labor saving of observation -." Proceeding of the 64th Hokkaido Development Technology Conference, Sapporo, Japan, pp. 320-325.

Usuda, C., and Takahashi, K. (2021) "Measurement line setting for labor saving of high water flow observation - study for introduction of next generation flow observation -." Proceeding of the 65th Hokkaido Development Technology Conference, Sapporo, Japan, pp. 835-840.

Information

Publisher :KOREA WATER RESOURECES ASSOCIATION
Publisher(Ko) :한국수자원학회
Journal Title :Journal of Korea Water Resources Association
Journal Title(Ko) :한국수자원학회 논문집
Volume : 58
No :3
Pages :277-286
Received Date : 2025-01-03
Revised Date : 2025-02-05
Accepted Date : 2025-02-06
DOI :https://doi.org/10.3741/JKWRA.2025.58.3.277

Journal of Korea Water Resources Association ISSN:2799-8746(Print) 2799-8754(Online) 한국수자원학회 논문집

All Issue