An open channel flow can be defined as a fluid flow through an open area, like a stream, or a canal. Sometimes even with closed pipe flows it is beneficial to pass the flow through an open channel to monitor flow rate and water quality.
Typically flow rates in open channels are measured by passing water over a weir or through a flume. A weir is a small overflow dam which creates a pool behind it and redirects the flow of water. Flow rates can be determined by measuring the height of the water flow over the weir notch (the weir in the picture above is the triangular patterned dam, and the notch is the node between the two peaks). A flume is an artificial channel which uses gravity and free flow pressure to pass water through (the picture below is of a Parshall Flume, which is one of the most widely used flumes). The flow rate is determined by measuring the speed and height of the water in the channel.
Along with different flume and weir options there are also many different types of measuring devices. There are Ultrasonic transducers, submerged probes, bubblers, area-velocity flow meters, floats, and differential pressure gauge. The most commonly used devices are ultrasonic transducers, which use sound waves to determine the speed and height of a fluid flow. Bubblers are also popular and measure flow by determining the amount of pressure needed to push a bubble into the flow, which is related to the height of the water in the flume. Below is a photo of a large Parshall flume with an ultrasonic transducer sensor and bracket installed (please also notice the staff gauge featured in last week’s article).
Here at Virtual Polymer Compounds we are experts in the field of open channel flow measurement. We are here to build a complete one step package for all of your needs. We have almost every type of flume available for immediate delivery. Customized packages are designed and built to suit any need or application, and will fit within your budget. Please call us today for information or to request a free quote!