CONCRETE FLUME CALCULATOR FREE
CONCRETE FLUME CALCULATOR FOR FREE
The introductory Parshall flume article mentioned above has diagrams and specifications showing the specified locations in the Parshall flume for measurement of Ha and Hb.Ī summary of the conditions required for free flow through a Parshall flume are as follows: The submergence ratio, S, is defined as Hb/Ha, where Ha is the head measurement needed for free flow calculations, measured at a point 2/3 of the length of the straight-sided converging section upstream from the beginning of the Parshall flume throat, and Hb is the head measured at the throat. The conditions for free flow through a Parshall flume are specified in the form of a maximum submergence ratio for each of several ranges of throat widths. Image Credit: Montezuma Valley Irrigation Company In the past, however, it was common to design Parshall flumes for 90% submergence, so there are still many flumes operating for open channel flow measurement under submerged conditions. Good practice calls for design of Parshall flumes to operate under free flow conditions because the flow rate can be measured more accurately and only one head measurement is needed. When the downstream flow “backs up” into the flume, obscuring the hydraulic jump, the flow is said to be submerged. Of the Parshall flume during free flow conditions. A hydraulic jump will be visible in the throat
When the flow through a Parshall flume is unaffected by flow conditions downstream of the flume, there is said to be “free flow” through the flume. For more background about the Parshall flume for open channel flow measurement and specifications for its dimensions, see the article, “ Open Channel Flow Measurement 2: the Parshall Flume.” Free Flow and Submerged Flow Through Parshall Flumes
Using the Excel formulas in the spreadsheets that can be downloaded from links later in this article, the flow rate through a Parshall flume can be calculated for both free flow and submerged flow conditions, in either U.S. Parshall flumes also have less head loss than weirs for open channel flow measurement. The Parshall flume is an open channel flow measurement device that is well suited for flows containing suspended solids because it tends to be self-flushing. Excel Formulas for Open Channel Flow Measurement Calculations with Parshall Flume Equations
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