Abstract
Circular crested weirs consist of a circular crested of upstream and downstream walls. These weirs are widely used in hydraulic engineering as water discharge structures and can be used to control water level in channels and tanks. In the present study, using Flow3D software, hydraulic properties were investigated to find weir geometry optimization through CFD method. Also, this study attempted to investigate flow on some sections of circular crested weirs in 3 groups and 11 models. Upstream and downstream slope changes as well as the height of the weir were also studied. To validate the model, laboratory models were used. In the research, flow depth parameters on crest, pressure distribution, velocity distribution, energy loss on circular crested weirs, as well as the height and changes of upstream and downstream slope were evaluated. Flow depth on the body of circular crest in this state is about 0.71 (H1). Upstream slope changes on flow depth on the weir’s crest revealed that increasing upstream slope causes to the increase of flow relative depth (H1/R) on the crest about 62%. Downstream changes in H1/R values less than 0.7 have no significant effect on discharge coefficient; however, increasing H1/R values seems to cause more change in slope.
Highlights
At the late 19th century and at the beginning of the 20th century, cylinder weirs were common before ogee spillways
During the 19th century, the attempt to improve the capacity of weirs’ discharge capacity leads to designing circular crested weirs. Due to their affordability and easy construction compared to other weirs, circular crested weirs can be used to measure the intensity of flow as well as water discharge structures in channels and tanks
The findings revealed that in a constant load, circular crested weirs have a higher discharge capacity compared to broad crested and sharp edge weirs
Summary
At the late 19th century and at the beginning of the 20th century, cylinder weirs (circular crested weir without upstream and downstream slopes) were common before ogee spillways. He employed k-Ɛ standard model and RNG for simulation [11] In their studies, Heidarpour et al (2005) investigated pressure changes on laboratory weir’s crest using some circular crested weirs. The results obtained from laboratory analyses revealed that pressure correction coefficient (pressure measured to hydrostatic pressure) was increased by increasing upstream slope but it was not changed by increasing downstream slope [12] In their studies on circular crested weirs, Bina and Beigipour (2005) reported that submergence coefficient of KS in these weirs only depends on weir’s submergence percentage and increasing submergence percentage of (H2/H1) leads to the decrease of KS coefficient. In flow simulations on circular crested weirs, various turbulence and boundary conditions of computational cell grid have been considered as in flow boundary with flow discharge, flow depth, etc. and out flow boundary and lateral walls of computational cells were considered in wall and symmetry, and floor and ceiling of computational cells grid were conspired wall and symmetry
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