BROAD-CRESTED WEIRS 



161 



that where the nappe adheres to the top but not to the down-stream 

 face of such a weir, the discharge may be expressed by 



Q = K' b H%, where K' K I -70 + '185 ?[ , 



w) 





FlG. 89A. 



Here K is the coefficient for the corresponding thin-crested weir, as 

 calculated from Bazin's formula. 



For wider crests, and for heads greater than 1/5 feet, this formula gives 

 rather low results, while if applied to the Francis formula, the results are 

 much too low for crest widths greater than 3 feet and for heads greater 

 than 1 foot. 



H.A, M 



