2/7/2024 0 Comments Flume definitionOpenchannelflow manufactures the following styles of short-throated flumes: "Short" does not refer to the flume length but to the fact that flow is controlled in a specific region of the flume to produce the level-to-flow relationship. Parshall began his investigation on his Improved Venturi flume, two distinct classes (and numerous styles) of flumes have been developed. While not all flumes have discharge sections ( H / Montana Flumes), the lack of this section means that the resistance to submergence is limited and that the downstream channel may be susceptible to scour and erosion as the flow spills off the end of the flume.The discharge section (light blue) slows the now energetic super-critical flow and transitions it into the downstream channel.The throat (gray) of the flume accelerates the flow to a critical / super-critical state. It is here that the point of measurement (H a) is located. Flow in the converging section must enter at a sub-critical state.Flow is restricted in the converging section (dark blue) and is accelerated as it passes into the throat.Most flume styles consist of three parts: a converging section (inlet), a throat, and a discharge section (outlet). Less head loss (~1/4 th that of a weir)Īlso, most flumes are resistant to changes or restrictions in the downstream hydraulics (submergence) - something not found with weirs.The ability to measure higher flow rates than a comparably sized weir.While having similar accuracy, flumes have distinct advantages over weirs, including: This accuracy is similar to that of weirs - although weirs are slightly more accurate under ideal conditions. With proper installation, flumes can be accurate to +/-2-5% (for the flume itself) however, overall system accuracy is +/-10% when all factors are considered. The relationship between the water level at the point of measurement (H a) and the flow rate can be obtained by test data ( short-throated flumes) or derived formula ( long-throated flumes). Flumes are static in nature - having no moving parts - and develop a relationship between the water level in the flume and the flow rate by restricting the flow of water in various ways.įlumes can accelerate slow, sub-critical (F r1) by:Īccelerating slow flow to a supercritical state creates upstream conditions where - under free-flow conditions - the flow rate can be determined by measuring the water level at a single, defined point in the flume (H a). Flumes are specially shaped, engineered structures used to measure the flow of water in open channels.
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