Abstract
A large collection of laboratory measurements of piezometric head (h) and discharge (Q) were made over hydraulic models of a tilting weir at nine different angles, ranging from 25.7° to 90° within a 0.3-m-wide flume. These measurements were corroborated with additional laboratory data taken within a 1-m-wide flume across four inclination angles. The range of both inclination angle (θ) and flow scale examined in this study elucidate the nature of the head-discharge rating equation beyond previous work. Results show that as θ decreases under a constant Q, the h over the weir decreases in a monotonic fashion due to the shallower angle of attack of the flow, which results in less curvature of the streamlines over the crest and therefore less deviation from the upstream hydrostatic pressure condition. To incorporate this effect into the head-discharge rating equation, a transformation of the h term was applied by multiplying the measured h that occurs over a tilting weir by a correction factor to match the effective h that would occur if the weir were aligned perpendicular to the flow at the same discharge. Thus, a modified form of the classical sharp-crested weir rating equation can be used as a means for determining the value of Q for tilting cases to a high degree of accuracy. The degree of accuracy is dependent on dimensionless Reynolds and Weber numbers describing the flow inertia in the approach to the weir in relation to respective viscous and surface tension scale effects. This approach portends marked flow measurement enhancement for flow conditions above a suggested inertial threshold.
Recommended Citation
J. E. Pugh et al., "A Novel and Enhanced Calibration of the Tilting Weir as a Flow Measurement Structure," Journal of Hydraulic Engineering, vol. 150, no. 2, article no. 04023064, American Society of Civil Engineers, Mar 2024.
The definitive version is available at https://doi.org/10.1061/JHEND8.HYENG-13796
Department(s)
Civil, Architectural and Environmental Engineering
International Standard Serial Number (ISSN)
1943-7900; 0733-9429
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2025 American Society of Civil Engineers, All rights reserved.
Publication Date
01 Mar 2024
Comments
Colorado Agricultural Experiment Station, Grant COL00424