Let’s get fluent session 2 (at BITS Pilani)
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Transcript of Let’s get fluent session 2 (at BITS Pilani)
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