Li-Chuan Chen, Marian Muste, and Larry Weber 53:071 Principles of Hydraulics Laboratory Experiment #4 Weir Calibration Li-Chuan Chen, Marian Muste, and Larry Weber

Objective To determine the head-discharge relationship of three different shapes of weirs, and to compare the experimental results with their corresponding analytical expressions.

Principle

Principle Slope Intercept

Apparatus — Flume

Apparatus — Weirs

Procedures Insert the weir of the desired shape. Record the reference point of the weir. Set the appropriate discharge in the flume. Record the water surface elevation upstream of the weir Repeat Steps 3 and 4 for four more discharges. Repeat Steps 1 to 5 for two more weir shapes.

Data Sheet Discharge Triangular 60 h (ft) Q (cfs) Ref. Point (ft) W.S. Elev. Weir Head  

Analysis Determine the discharge Q in the flume (using the side-contraction meter) and the head H on the weirs. Using several measured Q-H pairs, plot log Q versus log H. From the best-fit line to the experimental points, determine the kexp (the intercept) and nexp (the slope). Compare kexp and nexp with values indicated in the literature.

Sample Result

Further Considerations Derive, analytically, the head-discharge relationship for each of the weir shapes. If data seem to imply nexp  ntheory, why?