Which parameters are needed to check the hydraulic efficiency of lined trapezoidal shape irrigation channel. Is Hydraulic radius R affecting the hydraulic efficiency of channels
Well,
As shown in equation,
V = (1/n) 1.49 R2/3 S1/2, the hydraulic slope and hydraulic radius affects the efficiency of channel(water velocity).
Regards
Three items playing role in hydraulic efficiency:
1- Roughness: all lumped in the Manning's n but it can be due to material roughness of the wall material or "form drags" of the channel bed or meandering.
2- Geometry of cross section: it is given as hydraulic radius, a measure of how minimum (or maximum) is wetted perimeter compare to the are of cross section.
3- Bed slope S_0 (not hydraulic slope S_f). Only and only in uniform flow S_0 is equal to S_f. It is a measure which shows with what rate flow gains energy from gravity.
Hope it helps,
Kaveh
Hydraulic efficiency characterizes the pressure loss per unit length.
Head losses depend on the roughness of the canal walls, the slope of the canal bottom and the wetted perimeter of the canal.
Therefore, with an increase in the hydraulic radius, the surface friction of water against the channel walls increases, i.e. hydraulic radius affects hydraulic efficiency. The specific value is determined by calculation.
For constant canal slope, efficiency of canal can be satisfied with best hydraulic section.
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