How do you calculate flume flow rate?
For free flow, the equation to determine the flow rate is simply Q = CHan where:
- Q is flow rate (ft3/s)
- C is the free-flow coefficient for the flume (see Table 1 below)
- Ha is the head at the primary point of measurement (ft)
How do you size a Parshall flume?
Parshall Flumes have an hourglass shape. The waist – or narrowest portion of the flume – is defined as the throat. As Parshall flumes have rigid, defined dimensions (per ASTM D 1941 and ISO 9826). So long as the flume conforms to these standards, the flume size can be checked by the throat width alone.
How do you read a Parshall flume?
How to Read a Parshall Flume
- Inspect the Site. Are there any obstructions upstream of the flume?
- Watch the Flow. Watch the flow entering the flume.
- Inspect the Flume. Is the flume level from front-to-back and from side-to-side?
- Find the Point of Measurement.
- Read the Water Level.
How accurate are Parshall flumes?
Parshall Flume Accuracy Under laboratory conditions, Parshall Flumes can be to be accurate to within +/-2%. However, practical considerations such as approach flow, installation, and dimensional tolerances result in free-flow accuracies of +/-5% (per ASTM D1941).
How do you calibrate a Parshall flume?
Waste Water: Calibrating a Parshall Flume
- Ultrasonic level transmitter. Install an ultrasonic level transmitter to measure the height of water in the throat of the flume.
- Determine flow type. Two conditions of flow can occur through a Parshall flume: free flow and submerged flow.
- Measure velocity with a pitot tube.
What is the use of Parshall flume?
The purpose of a Parshall flume is to measure the flow of water in an open channel (or non-pressurized pipe). This water can be from a variety of sources, including: rivers, streams, canals, channels, field runoff, mine discharge, dam seepage, springs, wastewater, and industrial discharges.
What is Parshall flume flow meter?
The Parshall Flume is an economical and accurate way of measuring water flow in open channels and non-full pipes. Originally the flume was developed to measure surface waters, water rights apportionment, and irrigation flows.
What is the purpose of a Parshall flume?
Why are Parshall flumes the most common flow measuring devices?
Parshall Flumes are commonly used for a number of reasons: Most municipal operators are exposed to them during their initial training. The flat bottom makes determining the water level simple and straightforward. The Parshall Flume has a single point of measurement.
What is the meaning of Parshall?
Definition of Parshall : a device for measuring flow in conduits by observing difference of head on opposite sides of a partial obstruction.
What are the advantage disadvantage and uses of Parshall flume?
The advantages of the Parshall flume are: (1) it passes sediment and small trash easily, (2) it requires only a small head loss, and (3) it allows accurate flow measurements even when partially submerged. A disadvantage of the Parshall flume is that it is not accurate at low flow rates.
How to find the flow rate through a Parshall flume?
This calculator finds the flow rate through a Parshall Flume. A Parshall flume has particular dimensions. It can be identified by both a section that has a contraction in the width of the flume as well as a dip in the elevation of the bottom of the flume.
What is the plan view of a Parshall flume?
As seen in the picture at the right, the plan view of a Parshall flume is similar to that of a venturi flume, with a converging section, a throat, and a diverging section. A Parshall flume, however, also has prescribed variations in the channel bottom slope as shown in the diagram in the next section.
What is the size of a Parshall flume?
The size of a Parshall flume is designated by its throat width. Dimensions are available for Parshall flume throat widths from 1 inch to 50 ft. The 1 inch flume will carry a flow of 0.03 cfs at 0.2 ft of head, while a 50 ft Parshall flume will carry 3,000 cfs at a head of 5.7 ft.
How do you measure open channel flow rate?
Open Channel Flow Measurement. Open channel flow rate measurement is usually done by measuring a change in water depth. It can be done with a weir or flume. Common types are the sharp crested weir (including V-notch weir, rectangular weir, and cipolletti weir), the broad crested weir, the Parshall flume and venturi flume.