![parshall flume parshall flume](http://1.bp.blogspot.com/_QKGGYVMYiQE/StZw9ttKxhI/AAAAAAAAAC4/s0_ovcsJwdM/w1200-h630-p-k-no-nu/Parshall_Flume.jpg)
To find the second point of measurement, you’ll have to look at the throat or the narrowest part of the flume. For submerged flows, you’ll have to measure at the primary point of measurement and the secondary point expressed as Hb. You’ll just have to take an extra measurement. Parshall flumes are relatively unique, however, in that they can account for submergence.
![parshall flume parshall flume](https://www.engineeringexcelspreadsheets.com/wp-content/uploads/2011/04/Parshall-Flume_Plan-and-Elevation-Views.jpg)
Submergence isn’t only when the flume is completely underwater it technically refers to any kind of conditions that restrict the free flow of water out of the flume. Submergence is a potential problem for all flumes.
![parshall flume parshall flume](https://sc02.alicdn.com/kf/Hbf7009cff1a648e0a8babdd038af9bc11/220V-portable-river-flow-meter.jpg)
Fortunately, there are a few ways to condition the approach flow to make sure it has the right conditions, like the use of stilling wells or energy-absorbing manholes. If the flow isn’t uniform or is already supercritical, then the measurement won’t be very accurate when determining flow rate. The flume only works properly when faced with normal flow conditions, which means a flow that is approaching with a uniform subcritical velocity. Specifically, you’ll find it at about two-thirds of the converging section’s total length. It’s important to remember that this point of measurement isn’t actually at the throat of the flume but rather in the converging section upstream of the throat. The depth of the flow at this point is the variable that determines the flow rate. Once the flow rate has been increased properly, a measurement is taken at the Ha, which is the primary point of measurement. The parallel sidewalls contract and the floor drops in the throat section. This is accomplished thanks to its clever hourglass design shape. The most important thing to remember is that they accelerate the flow to a point of criticality where a measurement is taken to correspond with the flow rate. How a Parshall Flume Worksīefore you can grasp the advantages and disadvantages of Parshall flumes, you’ll need to learn how they work. Take a look at the advantages and disadvantages of a Parshall flume, and discover whether it would be the best fit for your needs. There are plenty of advantages and disadvantages to consider before committing to what should be your permanent flow rate measurement solution. Before you get one for yourself, however, you’ll need to make sure that it can offer the kind of measurements you’re looking for. The design of a Parshall flume is useful for permanent installations in surface water and irrigation flows. Being a staple for wastewater treatment and other industries where flow rate measurement is necessary, Parshall flumes have been a go-to design for decades. While they all have something special to offer, Parshall flumes are among the most common and well-researched. These measurements are taken by providing stilling wells at the entrance and throat.A flume is one of the best ways to take flow rate measurements, but there are quite a few different kinds of flumes to choose from. To measure discharge in submerged Venturi flume, two head measurements are required, one at the entrance and one at the throat. So, it is said to be submerged Venturi flume. Here, the downstream level of flume is kept equal to the level of throat section hence, there may be backward flow into the throat section.
![parshall flume parshall flume](https://tracomfrp.com/wp-content/uploads/Flume-Parshall-SelfSupport.jpg)
Submerged Venturi flume consists of gradual contraction on its upstream throat section in the middle and the gradual expanding section from the throat. Metering flumes are classified into following types : Different types of metering flumes and their working is explained in this article. Flumes are of different types and can be made up of materials such as aluminum, fiberglass, steel, wood etc. A Metering flume or flow measuring flume is an artificial channel section which is used to measure the discharge of a channel.