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  4. More Von Karman Vortex Street Movies

More Von Karman Vortex Street Movies

Laminar flow, Re 250

Lower Reynolds number. Note the larger wake and the pronounced vortex street.

Velocity vectors

Temperature

Cylinder wall heated, cold flow

Vorticity

Result is postprocessed in VisIt using “vorticity = 0.5*dot({0,0,1},curl(nvelocity))”

Other details

Detail of the velocity vectors immediately behind the cylinder

Turbulent flow, Re 20,000

Higher Reynolds number, the viscosity lowered to 0.0001. Note the smaller wake and the less pronounced vortex street.

Velocity vectors

Temperature

Cylinder wall heated, cold flow

Vorticity

Result is postprocessed in VisIt using “vorticity = 0.5*dot({0,0,1},curl(nvelocity))”

Other details

The velocity magnitude

Pressure

In the stagnation point it reads 0.5 Pa

Turbulent kinetic energy k

Turbulent dissipation rate epsilon

Turbulent kinetic energy k and the turbulent dissipation rate epsilon combined result in the effective viscosity

The turbulent kinetic energy k is a measure of the turbulent fluctuations and they can be related to the velocity magnitude giving the turbulent intensity i

Result is postprocessed in VisIt using “intensity = sqrt(0.66666) / (max(,0.001)) * 100.0”

From the turbulent kinetic energy k and the turbulent dissipation rate epsilon the turbulent length scale l can be derived

Result is postprocessed in VisIt using “length_scale = 0.09^0.75 * ^1.5 / ”

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