First, we can conclude that our results are coherent with the physical approach and the experimental results.


- Comparison Physics Knowledge / Numerical simulation
Thanks to our modelisation, the different flow patterns depending on Reynolds number value are observed. The most important result is the visualisation of the hydrodynamic instability called "Strouhal Instability" or "Von Karman Vortex Street".


- Comparison Experimentation / Numerical simulation
Thanks to a probe placed just above the cylinder, we visualise the average velocity magnitude. For a Reynolds number greater than a value called 'critical Reynolds number', the amplitude of the signal becomes sinusoidal. Analysing this signal for different Reynolds number, we found Rec = 40 in according to the experimental observation.



Secondly, we can interpret our results about Von Karman Vortex Street.

The observation of the beginning of the instability can be explained :
- mathematically, by the theory of the instability
- physically by the boundary layer separation
The propagation of the eddies shed behind the circular cylinder is due to the shape of the velocity profile.



Finally, the numerical simulation is a good way to understand the physical aspects of this instability and, changing inlet velocity magnitude, we can easily observe the different flow patterns and particularly the transition to turbulence.



Access to frame

ESPEYRAC Lionel
PASCAUD Stéphane
Presentation
Physics Knowledge
Numerical Simulation
Results Validation
Conclusion

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