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Navier-Stokes. Viscosity. A static fluid cannot support a shear. A moving fluid with viscosity can have shear. Dynamic viscosity m Kinematic viscosity n. F. v x. y. Pipe. Steady flow in a pipe involves viscosity. The forces must be balanced. z. a. l.
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Viscosity • A static fluid cannot support a shear. • A moving fluid with viscosity can have shear. • Dynamic viscosity m • Kinematic viscosity n F vx y
Pipe • Steady flow in a pipe involves viscosity. • The forces must be balanced. z a l
The flow in the pipe can be integrated. Zero velocity at the wall Another integration gives the total current. Poiseuille’s Law Poiseuille’s Law
Strain Rate Tensor • Rate of strain measures the amount of deformation in response to a stress. • Forms symmetric tensor • Based on the velocity gradient
There is a general relation between stress and strain Constants a, b include viscosity An incompressible fluid has no velocity divergence. Stress and Strain
Navier-Stokes Equation • The stress and strain relations can be combined with the equation of motion. • Reduces to Euler for no viscosity.
Make assumptions about flow to approximate fluid motion. Incompressible Inviscid Irrotational Force from gravity Apply to Navier-Stokes The result is Bernoulli’s equation. Bernoulli Rederived