For flow over a plate, the variation of velocity with vertical distance y from the plate is given as u(y) = ay − by2 where a and b are constants. Choose the correct relation for the wall shear stress in terms of a, b, and μ.

Respuesta :

Shear stress is simply the component of stress coplanar with a material cross-section

The relation for shear stress is: [tex]\mathbf{\tau = \mu(a - 2by)}[/tex] or [tex]\mathbf{\tau = a\mu - 2by\mu}[/tex]

The variation of velocity is given as:

[tex]\mathbf{u(y) = ay - by^2}[/tex]

Differentiate both sides with respect to y

[tex]\mathbf{u'(y) = a - 2by}[/tex]

The shear stress is calculated as:

[tex]\mathbf{\tau = \mu \times u'}[/tex]

Substitute [tex]\mathbf{u'(y) = a - 2by}[/tex]

[tex]\mathbf{\tau = \mu \times (a - 2by)}[/tex]

[tex]\mathbf{\tau = \mu(a - 2by)}[/tex]

Open bracket

[tex]\mathbf{\tau = a\mu - 2by\mu}[/tex]

Hence, the relation for shear stress is: [tex]\mathbf{\tau = \mu(a - 2by)}[/tex] or [tex]\mathbf{\tau = a\mu - 2by\mu}[/tex]

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