Author: Paul MannevillePublisher:
ISBN:
Category :
Languages : en
Pages : 18
Book Description
This lecture presented a scenario of transition to turbulence specific to large aspect ratio systems. Starting with simulations on a model chosen for its relevance to the field of convective instabilities we characterized the spatio-temporal intermittent 'phase'. Then we examined the transition process having recourse to simpler systems: coupled maps lattices. This process appeared to involve the propagation of an information, laminar/turbulent which seemed stochastic though it was generated by a deterministic dynamics. Concepts first introduced in the statistical physics of critical phenomena applied to directed percolation allowed us to account for most features of spatio-temporal intermittency, and especially the change of behavior at what turned out to be a true threshold. The implications of this approach are important because, in large aspect ratio systems, we have to face the possibility that what we think is turbulence may be simply a finite life-time but very long turbulent transient. If the percolation analogy is valid, then a threshold exists above which the turbulent state percolates through the system and turbulence has virtually no chance to decay.
