Let’s Get FLUENTSession 2

The Karman Vortex Street Simulation

Karman Vortex StreetRepeated shedding of swirling vorticesCaused by unsteady separation of flow over

a bluff bodyResult of form drag and not viscous dragSome jargon: wake, vortex, recirculation,

bluff body

In real life..

Pictures from Wikipedia

What exactly happensThe wake of the bluff body may become

unstable due to a very small perturbation in the flow

Once asymmetry is induced its magnified several fold and one vortex is shed

Causes asymmetric pressure distribution and the pattern repeats

Phenomenon normally observed at low Reynolds Numbers (90+)

Some QuantificationFrequency of shedding:

Reynolds Number:

Total Heat Transfer Rate: (h)(A)(dT)

<Open Spreadsheet>

Flow Parameters V d Ro Mu Re

0.1 0.05 0.9885 2.28E-05 2.17E+02

Vortex Shedding Time Scalef T

3.60E-01 2.78E+00

Calculations for Total Heat Transfer RateNu 8.564286454Pr 0.7Re 2.17E+02k 0.03h 5.138571872dT 123A 0.157079633Q 99.28129281CFD Q 91.9error % 7.434726727

Sample Calculation