Venturi Flume – What It Measures in Open Channels A Venturi flume is an open-channel primary device that accelerates flow through a throat to relate water level to discharge using calibrated curves.

Introduction:
Venturi flumes are widely used for flow measurement in irrigation canals, wastewater channels, and environmental monitoring. They produce a known head-discharge relationship by constricting the cross section and monitoring upstream and throat depths.

Given Data / Assumptions:

• Free-surface open-channel flow under gravity.
• Properly installed Venturi flume with standard geometry.
• Calibrated relationship between measured head(s) and discharge.

Concept / Approach:

By continuity and energy principles, accelerating flow through a throat changes depth and velocity in a predictable way. Empirical or semi-theoretical calibration provides Q as a function of measured head. Unlike Venturi meters for pressurized pipes, flumes operate with a free surface and measure discharge directly from level readings.

Step-by-Step Solution:

Verification / Alternative check:

Device manuals provide rating tables or equations. Field spot checks with current meters or dilution gaging confirm the flume discharge within stated accuracy when installation is correct.

Why Other Options Are Wrong:

Pressure measurement options relate to pressurized conduits or differential devices, not free-surface flumes. Fluid density is not measured by a Venturi flume.

Common Pitfalls:

Improper submergence conditions invalidating the free-flow equation; incorrect staff-gage locations; sediment deposition altering geometry.

Final Answer:

discharge of liquid