Experimental and Numerical Modelling of Flow Pattern on

آب و خاک

Article 16, Volume 24, Issue 1, March 2010   

Document Type: Research Article

DOI: 10.22067/jsw.v0i0.2937

Authors

K. Esmaili^{* 1}; B. Naghavi¹; F. Koorosh Vahid¹; J. Yazdi²

¹College of Agriculture, Ferdowsi University of Mashhad

²Water Research Institute

Abstract

Abstract
Weirs are the most common structures for discharge measurement in engineering research. Streamline curvature, non hydrostatic pressure distribution on weir and nappe adherence to the weir lead to differences between calculated and measured discharges. Thus discharge coefficient, which is the ratio of real and theoretic discharges, is usually less than unity. In circular weirs the pressure distribution and velocity differs from sharp crested weirs which affect on flow discharge and extend the discharge coefficient more than unity. In this study, pressure distribution and velocity of different circular weir measured in laboratory models and compared with Fluent simulation as a numerical code. The results showed significant relation between measured and simulated data. Also it is found that the critical flow depth and separated flow are located respectively before and after the crest of weir. Nappe separation depends on overflow discharge and will shift to the downstream face of the cylinder in high discharges. To recognize the location of critical flow conditions and nappe separations, theoretical formulations has is proposed. The equations are found to be dependent on weir size and inflow conditions. The theoretical predictions showed good agreement in comparison with experimental results.

Keywords: Circular weir, Velocity and pressure distribution, Nappe separation, Critical depth, Fluent