ESS227
Prof. Jin-Yi Yu
Frictional (Viscous) Force
• Force required to
maintain this flow
è
• For a layer of
fluid at depth δZ, the force is
è
•Any real fluid is subject to internal
friction (viscosity)
• Viscous force per
unit area (shearing stress):
è
•Stresses applied on a fluid
element
è
•Viscous force per unit mass due to
stress
è
•Frictional force per unit mass in
x-direction
è
stress acting on
the fluid below the box
stress acting on
the box from the fluid below