Hydraulics Engineering Engr. Muhammad Hassan Hassan25.arif@gmail.com

Best Hydraulic Channel

Objective of Channel Design Transport of water between two points in a safe and cost effective manner. Includes economical safety and aesthetic aspects. The channel having the least wetted perimeter for the given area has the maximum conveyance.

Only focus will be on hydraulic aspects Only focus will be on hydraulic aspects. Conveyance of a channel increases with hydraulic radius (Manning’s Formula). Hydraulic radius increases with a decrease in wetted perimeter. Best hydraulic section is the one having minimum wetted perimeter.

For a specific cross section, the proportion that produces the best hydraulic cross section (maximum flow) might be derived. The best hydraulic section might not be best from economical point of view.

The minimum permissible velocity is the lowest velocity that will prevent sedimentation and vegetative growth (0.6 to 0.9 m/s for sedimentation and 0.75 m/s for vegetation. The vertical distance from the top of the channel to the water surface is known as freeboard.

Assignment What about trapezoidal channel? What about circular channel?

Practice For a trapezoidal channel with base width 6.0m, side slope 1:2(V:H) , and n=2 , calculate the critical depth, critical velocity, and critical slope for Q= 17cumecs. A rectangular channel is 3m wide, has a 0.01 slope, flow rate of 5.3 cumecs , and n=0.011. find the normal and critical depths of flow.

Water flows in a rectangular channel at a depth of 1 Water flows in a rectangular channel at a depth of 1.22 m and flow rate of 5.66 cumecs. Determine channel width if the channel is sub critical. For a trapezoidal channel with base width b=3.0m , Manning's n=0.025 and side slope of 1V:2H, calculate the critical depth, critical velocity and critical slope if Q=10 cumecs.