The polar equation of the cross-section being

r^½ cos ½[theta] = a^½, or r + x = 2a, (3)

the conditions are satisfied by

[psi]´ = Ur sin [theta] - 2Ua^½ r^½ sin ½[theta]

= 2Ur^½ sin ½[theta](r^½ cos ½[theta] - a^½), (4)

[psi] = 2Ua^½ r^½ sin ½[theta] = -U[root][2a(r-x)], (5)

w = -2Ua^½ z^½, (6)

and the resistance of the liquid is 2[pi][rho]aV²/2g.

Encyclopaedia Britannica, 11th Edition, "Hydromechanics" to "Ichnography" Volume 14, Slice 2 · 第 36 / 120 题