{"id":500,"date":"2018-05-08T21:41:53","date_gmt":"2018-05-08T21:41:53","guid":{"rendered":"https:\/\/learn.hydrologystudio.com\/studio-express\/?post_type=ht_kb&p=500"},"modified":"2022-06-03T21:27:41","modified_gmt":"2022-06-03T21:27:41","slug":"weirs","status":"publish","type":"ht_kb","link":"https:\/\/learn.hydrologystudio.com\/studio-express\/knowledge-base\/weirs\/","title":{"rendered":"Weir Flow Calculations"},"content":{"rendered":"\n
\"weir<\/figure><\/div>\n\n\n\n

Studio Express uses a standard weir equation for Rectangular Sharp-crested, Compound, Cipolletti, Trapezoidal and Rectangular Broad-crested weirs.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Where:
Q = discharge over weir, cfs (cms)
L = length of the weir crest, ft (m)
H = distance between water surface and the crest, ft (m)
Cw = weir coefficient, typically 3.33 (1.84) for sharp-crested; 3.367 (1.83) for Cipolletti; 3.09 (1.7) for Broad-crested<\/p>\n\n\n\n

\"Calculating
Sharp<\/strong>-crested weir. Maximum crest thickness is <= 1\/2 depth.<\/figcaption><\/figure><\/div>\n\n\n\n
\"Weir
Broad<\/strong>-crested weir. Hydrostatic pressure is fully developed. Crest width is >= 2 x depth.<\/em><\/figcaption><\/figure><\/div>\n\n\n\n

Trapezoidal with Sloped Sides<\/h3>\n\n\n\n

Total flow over trapezoidal weirs with side slopes is computed using the standard weir equation as shown above, plus two times the flow given from the following equation.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Where:
Q = discharge over side-sloped portion of weir, cfs (cms)
Z = side slope (Z horizontal to 1 vertical) of the weir crest
H = distance between water surface and the crest, ft (m)
Cw = weir coefficient, typically 3.367 (1.83)<\/p>\n\n\n\n

\"Cipolletti
Cipolletti weirs have .25 H to 1 V side slopes, Z = 0.25.<\/figcaption><\/figure>\n\n\n\n

V-notch<\/h3>\n\n\n\n

V-notch weirs are computed using this equation:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Where: Q = discharge over weir, cfs (cms)
\u0398 = angle of v-notch in degrees
H = head on apex of v-notch, ft (m)<\/p>\n\n\n\n

Adjustment for Submerged Weirs<\/h3>\n\n\n\n

Weirs can be affected by submergence, i.e., when the user-inputted tailwater rises above the weir’s crest.<\/p>\n\n\n\n

\"\"The equation for the reduction in flow is:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Where:
Qs = submerged flow, cfs (cms)
Qr = unsubmerged flow from standard weir equations, cfs (cms)
H1 = upstream head above crest, ft (m)
H2 = downstream head above crest, ft (m)<\/p>\n\n\n\n

\"Submerged
Submerged weir<\/figcaption><\/figure><\/div>\n\n\n\n
\n\n\n\n

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