Abstract
Water discharge assessment in open channel flow is one of the most crucial issues for hydraulic engineers in the fields of water resource management, river dynamics, ecohydraulics, irrigation, and hydraulic structure design, among others. Recent studies state that the entropy velocity law allows expeditive methodology for discharge estimation and rating curve development due to the simple mathematical formulation and implementation. Many works have been developed based on the one-dimensional (1-D) formulation of the entropy velocity profile, supporting measurements in the lab and the field for rating curve assessment, but in recent years, the two-dimensional (2-D) formulation was proposed and applied in studies of regular ditch flow, showing good performance. The present work deals with a comparison between the 1-D and 2-D approaches in order to give a general framework of threats and opportunities related to the robust operational application of such laws. The analysis was carried out on a laboratory ditch with regular roughness, under controlled boundary conditions, and in different stages, generating an exhaustive dashboard for better appraisal of the approaches.
Highlights
Valuation of water discharge in open channel flow is relevant to hydraulic engineering in several research and operative fields related to irrigation, river monitoring and control, water resource management, hydrological balance assessment and modeling, and calibration of ordinary and advanced runoff and flooding routing models
The wide wide set set of of measurements measurements obtained obtained through through the the laboratory laboratory experiments experiments and and the the literature literature allow us to perform a robust comparison between the entropy velocity profiles, allow us to perform a robust comparison between the 1-D and 2-D entropy velocity profiles, in in order order to to obtain obtain suitable suitable information information for for use use in in the the operative operative chain chain for for water water discharge discharge assessment assessment and and computational computational open open channel channel flow
With respect to water discharge assessment, both models have good performance, as velocity profile is physically consistent with the sidewall effect, which induces a no-slip condition on reported in Figure 6, which shows a comparison between the measured discharge and those obtained fluid particles while it is implicitly neglected in the 1-D case
Summary
Valuation of water discharge in open channel flow is relevant to hydraulic engineering in several research and operative fields related to irrigation, river monitoring and control, water resource management, hydrological balance assessment and modeling, and calibration of ordinary and advanced runoff and flooding routing models. It allows a definition of the relationship expressing M as dependent on the hydraulic radius, Manning’s roughness, and the location of the zero horizontal velocity, generally defined as y0 For the latter, it was found that if y0 is assessed by distinguishing low flows from high flows, a better estimation of M might be obtained across a gauged river site. Considering that the y0 location is not a simple assessment and could have high uncertainty, assessment of M should be allowed using easy-to-acquire hydraulic and geometric variables, mainly for ungauged river sites This could be achieved by looking at the relative submergence D/d (where D is average water depth and d is the characteristic dimension of the roughness elements). The results support and validate a robust and fruitful operative chain to be implemented for expeditive water discharge assessment in rough and smooth irrigation ditches at different stages, allowing assessment of the local rating curve
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