Adjusting a Parshall Flume for High Approach Velocity

Parshall flumes are perhaps the most widely used open channel flow device in the world. The benefit of this style of flume is that it can be used in a variety of applications, and it is also resistant to some of the drawbacks that can affect other devices. There is one issue, however, that may impact the usefulness of your flume: high approach velocity.

While Parshall flumes are not as influenced by approach velocity as other devices, extremely high velocities can impact the functionality of your flume. Fortunately, there are several options for correcting this issue. Here are a few ways you can adjust for high approach velocities with Parshall flumes so that you can be sure that your device functions the way you want and need.

Adjusting Throat Width

The reason that correcting for high velocity is important is that if the flow velocity is too high, taking accurate readings will be nearly impossible. One of the easiest ways to decrease approach velocity so that you can take your measurements is by reducing the throat width of your flume.

Using a flume with a smaller throat can decrease approach velocity so that your measurements can be accurate. The drawback is that this solution really only works in a natural channel. Also, using a narrower throat width will cause the water level to rise, which may impact upstream conditions.

Existing Installations

Installing a flume with a smaller throat can be a good choice for new flume installations. If you already have a flume in place, however, you will need another solution. Fortunately, there are several different options you can choose to adjust for high approach velocities with Parshall flumes for existing systems.

A simple method for reducing velocity in a preexisting flume is installing an energy absorber. These flume accessories are designed for installation directly inside of a flume and work to condition the flow and decrease velocity. Adding an energy absorber to your Parshall flume will allow you to very quickly correct a high approach velocity so that your flume will function properly.

Another way that you can adjust approach velocity if you already have a flume in place is to use nested flumes. Basically, this means that you would install a second, smaller flume inside of your original device. A nested Parshall flume can be easily added in most applications, and should allow you to effectively condition the velocity of your approaching flow.

Invest in a Parshall Flume

Making sure to adjust for high approach velocities with Parshall flumes is the most important thing you can do to get the most out of your device, and as you now know, there are multiple ways to achieve this goal. If you need to install a Parshall flume in your system, you can easily purchase your device by shopping the Tracom, FRP catalogue.

With Tracom, you’ll find Parshall flumes in a wide range of sizes and styles, as well as accessories that can help you get the most out of your flow management device. Contact us today if you have any questions about our Parshall flumes or would like to request a quote.

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