The fluid exerts the tangential traction $-\tau\mathbf e_x$ on the upper boundary and $+\tau\mathbf e_x$ on the lower boundary. Equivalently, the boundaries exert $+\tau\mathbf e_x$ and $-\tau\mathbf e_x$ on the fluids, respectively.


Solution

Past exam of the mathematics course of the University of Cambridge / 2019 / ii / Paper 2 / 37A / b / i / Solution

 Solution (source code)