Computes hydraulic elements for a Circular Conduit using:
Angle = ARCCOS[1 - 2(y/D)] (in radians)
Area = (D^2/4)(Angle - SIN(Angle)*COS(Angle))
Topwidth = D*SIN(Angle)
Wetted Perimeter = D*Angle
Hydraulic Radius = Area/(Wetted Perimeter)
Hydraulic Depth = Area/Topwidth
Notes:
Entering y > D will generate an error
As y -> D, Topwidth -> 0, Hyd. Depth -> +INF