Hydrodynamic instabilities in general and Von Karmann vortex streets in particular are extremely complex phenomena which are often difficult to solve only by analytical methods : this is the reason why Fluent is necessary to visualize their formation and evolution.
However, it must be noticed that hydrodynamic instabilities cannot be correctly simulated by a calculation code since it never reproduces the real conditions under which the instability occurs. What is more, basical knowledges of the phenomenon are required to make relevant calculations. Indeed, the logical method for computing instabilities should be first to have a global idea of their characteristics, and then to make calculations. Unfortunately, the contrary more often happens : calculations are repeated several times in order to obtain the desired results, and the theoretical analysis is made later.
Nevertheless, Von Karmann vortex street is probably one of the most complex hydrodynamic instabilities, which has not been clearly analytically described up to now. Yet, even if one has no equation, it is conceivable to understand the global mechanism of this phenomenon by knowing some of its basical characteristics (formation of vortices for instance).
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