RBC flumes are small, portable long throated flumes designed specifically for use in small earthen channels and furrows. The five flumes are scale models of each other, with each flume possessing a trapezoidal throat varying in size, bc, from 50 to 200 mm [1.968 to 7.874-inches].
Flow Rates and Accuracy
While limited in size, RBC flumes exhibit accuracies on par with thin-plate weirs (2%) and are available to handle flows from 0.367 to 777.9 gpm [1.423 to 49.08 l/s].
One distinct disadvantage of RBC flumes is the upstream ponding that occurs due to throat ramp. Similar to the Palmer-Bowlus flume, there will always be standing water upstream of a RBC flume. This is in contrast to other flumes, such as the Parshall or Cutthroat, where flow is accelerated by a constriction of the sidewalls and / or a drop in the floor.
RBC Construction
As RBC flume are intended to be used on small flows and may be taken from site to site, cost and weight are considerations. RBC flumes are commonly constructed from galvanized steel or fiberglass, although the flume’s simple design lends itself well to other materials also.
RBC Design
The walls of a RBC flume form a trapezoid with the base of the trapezoid (the floor of the flume) 0.5 bc wide. The walls of the flume rise at a 1 to 0.5 slope and continue straight through the flume – there is no contraction of the sidewalls, as there is in Trapezoidal flumes.
Flow is accelerated through an RBC flume through the use of a raised trapezoidal ramp. The base of the ramp is 0.5 bc while the top is bc (the flume size). The ramp height is 0.5 bc. As flow approaches the throat, the ramp rises at a 1 to 3 slope for a distance of 1.5 bc. The flow then continues for another 1.5 bc, before dropping off the end of the ramp (who’s downstream section is a vertical drop – there is no down ramp as there is in a Palmer-Bowlus flume).
RBC flumes lack many of the options available in other flumes (particularly end adapters), although flat inlet wing walls are available to help span channels wider than the flume.
