OPEN CHANNEL FLOW

SHOW THAT FOR RECTANGULAR SECTION WIDTH IS TWO TIMES OF DEPTH

Steps to solve:

1. find perimeter of section in terms of width and depth.
2. Now convert the perimeter in terms of depth only.
3. for optimum, perimeter should be minimum.
4. for minimum differentiate perimeter with respect to depth(y)
5. from the above relation width is 2 times the depth(y)