By symmetry the pressure is the same as for a full cylinder, that is on the cylinder surface the pressure is given by
- for ,
and thus the lift force is given by
- = 1.67,
which gives a lift coefficient since the planform width of the cylinder is 2.
We compare with the maximal about 1.5 from measurements:
Not so bad!! You may think of the half cylinder as a sort of wing:
for which you have just computed the lift to be L = 1.67.