Repository logo

Flow field at open-channel contractions: insights from a two-dimensional numerical model




Zey, Scott S., author
Ettema, Robert, advisor
Nelson, Peter A., committee member
Covino, Timothy P., committee member

Journal Title

Journal ISSN

Volume Title


A depth averaged, two-dimensional numerical model was used to investigate the hydraulics of flow passing through open-channel contractions. The investigation focused on the magnitude and location(s) of maximum velocity of flow entering a contraction. The effective flow width at the entrance of the contraction and the maximum lateral velocity at the contraction entrance were also investigated. The responses of these flow characteristics were studied as values of contraction ratio, channel roughness, bed slope, and transition geometry were varied. The numerical model produced significant new insights. The factors affecting the values and distribution of velocity in a contraction include: channel slope, bed roughness, and contraction shape. The magnitude and location of maximum velocity in the contraction varies with contraction ratio. For contraction ratios milder than approximately 0.5 the velocity maximum occurs at two locations, and at one location for tighter contractions. At a contraction ratio of 0.5 lateral velocity reached a maximum and effective flow width a minimum. Channel slope and bed roughness affect the values and distribution of velocity in a contraction, as did contraction shape. These findings have engineering significance for explaining and estimating scour of alluvial channels in contractions, such as at bridge waterways.


Rights Access



Associated Publications