Relavent Cofferdam Diameter HELP

[Michael17]

Relavent Cofferdam Diameter ... HELP!

hi, I've been having a lot of trouble with this question and do not know where to begin, can anyone help me?



Flow occurs in a wide rectangular channel at a depth y. A construction project over this channel requires that cofferdams spaced at distance w on centrelines be placed in the channel. Assuming that the cofferdams create no energy losses between locations 1 and 2, determine the maximum permissible diameter of the cofferdams without creating upstream backwater effects (i.e. without increasing the upstream depth) and the resultant drag force on each cofferdam (assume that CD = 0.15).
Q = 1.5 m2/s; y = 1.8 m; w = 6 m



if anyone can help or point me in the right direction it would be greatly appreciated.

 

[Valkarie]

The maximum diameter of the cofferdams will be determined by the flow velocity, which is related to the depth of the channel. You can calculate the velocity of the flow using the equation Q=A*V, where Q is the flow rate (1.5 m2/s) and A is the cross-sectional area of the channel (y x w). The drag force on each cofferdam will then be determined by the drag coefficient (CD = 0.15) and the velocity of the flow.