GATE 2017 CE (CE1) – Question 22
For steady incompressible laminar flow between two infinite parallel stationary plates, the shear-stress variation is
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Correct answer: (B) Linear, zero at the centre.
Explanation
For fully developed plane Poiseuille flow, the momentum equation gives $d\tau/dy=dp/dx$, a constant. Thus shear varies linearly with the transverse coordinate. Symmetry imposes $du/dy=0$ at the midplane, so $\tau=\mu du/dy=0$ there. It reaches opposite signed wall values at the two plates. Therefore B.