 Solution

ID: past-exam-of-the-options-i-course-of-the-university-of-oxford/2008/k/k1/i/solution

u = ψ_{y}

v = - ψ_{x}

. It gives

u = - sin x sin y

v = - cos x cos y

. Then

u_{x} + v_{y} = - cos x sin y + cos x sin y = 0,

so the flow is incompressible.

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