Articles | Volume 19, issue 9
Research article
14 Sep 2015
Research article |  | 14 Sep 2015

Computation of vertically averaged velocities in irregular sections of straight channels

E. Spada, T. Tucciarelli, M. Sinagra, V. Sammartano, and G. Corato

Abstract. Two new methods for vertically averaged velocity computation are presented, validated and compared with other available formulas. The first method derives from the well-known Huthoff algorithm, which is first shown to be dependent on the way the river cross section is discretized into several subsections. The second method assumes the vertically averaged longitudinal velocity to be a function only of the friction factor and of the so-called "local hydraulic radius", computed as the ratio between the integral of the elementary areas around a given vertical and the integral of the elementary solid boundaries around the same vertical. Both integrals are weighted with a linear shape function equal to zero at a distance from the integration variable which is proportional to the water depth according to an empirical coefficient β. Both formulas are validated against (1) laboratory experimental data, (2) discharge hydrographs measured in a real site, where the friction factor is estimated from an unsteady-state analysis of water levels recorded in two different river cross sections, and (3) the 3-D solution obtained using the commercial ANSYS CFX code, computing the steady-state uniform flow in a cross section of the Alzette River.

Short summary
We present two new methods for uniform flow computation, named LHRM and INCM. We also present the calibration and first validation from laboratory experimental data, second validation by field discharge hydrographs estimated by measured water level data, and the third validation from a 3-D solution of CFX code applied to a reach of the Alzette River.