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V-notch angle weirs, the head is measured upstream of the weir plate at a 
minimum distance of 3 times maximum head to ensure the surface of the 
liquid is not effected by turbulence or drawdown. See Exponential devices, 
above, for further details. 
Calculations  
 
Palmer Bowlus Flume and H-Flume  
ABSOLUTE 
If the flow calculation is to be absolute P702 = 1 the flow will be calculated 
using the formula: q = f(h)
 
Where:  q   = flowrate                   
 f   = is an 8
th
 degree polynomial solution for h (head)    
RATIOMETRIC 
If the flow calculation is to be ratiometric P702 = 2 the flow will be 
calculated using the formula: q= q
cal 
f(h)/f(h
cal
) 
 Where:  q         = flowrate             
q 
cal      
= flowrate at maximum head P705    
f(h)     = a polynomial solution for h (head)  
f(h
cal
)  = a polynomial solution for h
cal 
(maximum head) 
 
V-Notch Angle Weir (Non-BS 3680) 
ABSOLUTE 
If the flow calculation is to be absolute P702 = 1 the flow will be calculated 
using the formula: q = C
e 
8/15 tan (theta/2)(2gn)
0.5
(h = kh)
2.5 
Where:  q       = flowrate                      
 C
e
 = discharge coefficient calculated by the Flow 5 P723                              
theta  = V-notch angle    
gn      = gravitational acceleration        
h        = head    
kh      = compensated head