Flow Simulation over Cylinder: Von Karman Vortex

The flow characteristics over a cylinder are one of the most applicable important topics of research. The cylinder subjected to low Reynolds number experiences flow separation, and oscillations in the wake region. The periodic nature of the vortex shedding phenomenon can sometimes result in unwanted structural vibrations, which leads to structural damage. A Von Karman vortex is a repeating pattern of swirling vortices arising in the wake of the flows around the cylinder. This process can be only seen at a particular critical Reynolds number.

These Vortices are created at the back of the body and they detach randomly from either side of the body. The fluid flow past the object creates alternating low-pressure vortices or eddies on the downstream side of the object. The object will tend to move towards the low-pressure zone and flow separation occurs results in a vortex generally found at Re above 40 but can be clearly seen at Re 100.

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Conclusion

1. Vortex shedding can be easily seen in the case of both Steady State and Transient Simulation. But Transient Simulation produces better results and more Realistic.
2. Strouhal Number calculation is only possible in the case of Transient simulation as the frequency changes with respect to time.
3. As the Reynolds number Increases, The drag Coefficient also Increases.
4. Drag force is inversely proportional to Reynolds number(Re<300 where the flow is laminar after that it gets converted to turbulent) on changing the viscosity.
5. Vortex shedding can be observed after Re 40.