Parshall flumes, like other types of flumes, require adequate approach conditions to offer accurate measurements of flow rate. In some flow channels, the proper approach conditions simply don’t exist naturally. Fortunately, you can alter the flow conditions in several different ways, and it’s particularly easy when using a Parshall flume. Discover how to dampen turbulence in Parshall flumes.
Energy Absorbing Manholes
If you’re looking to dampen the turbulence upstream from the flume, the best strategy is to implement an energy absorbing manhole. These manholes are placed upstream of the flume itself and solely exist to dissipate energy. This manhole would then be connected to the flume via a pipe which creates a subcritical flow with a full velocity profile on the way to the flume and point of measurement.
Manholes work on a variety of flows whether you’re dealing with something industrial, sanitary, or mixed. They can even be implemented in conditions with limited space and can account for high slopes. Because of their near-universal application, manholes are among the most popular solutions for pretreatment flow measurement.
Baffle plates are an in-flume solution for turbulence, but they’re applied differently depending on the size of your flume. In small flumes, for example, perforated baffle plates can be installed in the inlet end adapter. Since the perforation is set in a staggered pattern, it works to break up poor velocity profiles. Keep in mind, however, that these baffle plates are typically molded into the sidewalls and not something you add to an existing flume after the fact.
In large flumes, baffle plates tend to bend under the sheer pressure of the flow. Because of this, an alternative that accomplishes the same goal is implemented instead. Tranquilizing racks are set up similarly to baffle plates in that one is meant to disrupt the heavy flow while the other is meant to straighten out the flow to an even velocity profile.
In-Flume Energy Absorbers
There are energy absorbers you can implement within a flume rather than upstream like their manhole counterparts. These in-flume absorbers work a bit differently than upstream manholes as well since they have to account for surface turbulence. An upstream manhole doesn’t have to worry about that as much since the flow’s turbulence will be under control by the time it reaches the flume.
While not upstream of the flume itself, these energy absorbers are installed upstream of the flume’s converging inlet section. Be sure to include a top splashguard with your energy absorber to prevent excessive turbulence on the surface. You’re not restricted to just an energy absorber either. They’re often used in conjunction with other tools like tranquilizing racks.
Optimize Your Approach with Tracom
Now that you know how to dampen turbulence in Parshall flumes, it’s time to get the perfect solution to your flow channel conditions. At Tracom, we can help you get a custom Parshall flume that not only fits your channel but has the kit you need for accurate measurements with conditioned flows. Contact us today to get started!