TS 871

TS 871 is a terminology standard that establishes a common technical language for terms and symbols used in the measurement of liquid flow with a free surface. In open-channel flow applications, it helps align the vocabulary used for discharge, water level, cross-section, slope, and related measuring concepts so that engineering, design, and reporting work use the same meanings consistently.

Why terminology matters in free-surface flow measurement

Free-surface flow refers to situations where part of the liquid is in contact with the atmosphere, which makes it conceptually different from pressurised pipe flow. Measurement in this field is not limited to discharge alone; it also involves the geometric and hydraulic quantities that define the flow. Standardising terms and symbols helps different methods and calculations remain comparable and reduces confusion caused when the same quantity is named or symbolised differently across documents.

What this document covers

• It covers the terminology used in connection with measurements of liquid flow with a free surface.
• It provides a common vocabulary framework for the symbols associated with those measurements.
• It was published in the Turkish catalogue as the equivalent of ISO/R 772.
• The document has been withdrawn, so it should be treated as a historical terminology reference.

Vocabulary standards do not usually prescribe a test method or a performance limit on their own; instead, they define the boundaries of the concepts used by practitioners. In free-surface flow work, that common language supports channel hydraulics, flow observations, and related structures such as weirs and similar measuring arrangements. TS 871 provides that defining framework.