Inviscid flow

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Inviscid flow is a fluid flow where viscous (friction) forces are small in comparison to inertial forces, i.e. a flow with a Reynolds number . The assumption that viscous forces are negligible can be used to simplify the Navier-Stokes equations to the Euler equations.

In the case of incompressible flow, the Euler equations governing inviscid flow are:

which, in the stationary case, can be solved using potential flow theory. More generally, Bernoulli's equation can be used to analyse certain time-dependent compressible and incompressible flows.

[edit] Problems with the inviscid flow model

While throughout much of a flow the effect of viscosity may be small, a number of factors make the assumption of negligible viscosity invalid in many cases. Viscosity often cannot be neglected near boundaries because the no-slip condition can generate a region of large strain rate (a Boundary_layer) which enhances the effect of even a small amount of viscosity. Turbulence is also observed in some high Reynolds number flows, and is a process through which energy transferred to decreasingly small scales of motion until it is dissipated by viscosity.

[edit] See also

• Viscosity
• Fluid dynamics
• Stokes flow, in which the viscous forces are much greater than inertial forces.