Given the velocity potential of a flow, find the velocity v = ∇f of the field and its value v(P) at P. Sketch v(P) and the curve f = const passing through P.

At what points is the flow in Prob. 21 directed vertically upward?

Data from Prob. 21

Given the velocity potential of a flow, find the velocity v = ∇f of the field and its value v(P) at P. Sketch v(P) and the curve f = const passing through P.

f = e^x cos y, P: (1, 1/2π)