The Complementary Roles of Experiments and Simulation in Coherent Structure Studies

Abstract

The past two decades’ vigorous studies of coherent structures (CS) have failed to produce a consensus on what CS are, let alone a CS-based turbulence theory or even an objective, mathematical definition of CS. What started out as a promise for a mechanistic explanation for fluid turbulence—as researchers found or reinvented CS in their ‘search for order in disorder’ and presumed to have discovered a deterministic, tractable route to turbulence phenomena—has unfolded itself as a Pandora’s box. Successive studies of CS continue to raise more questions than they answer. Thus, even though we understand more about turbulence via CS concepts, we have become painfully even more aware of how complex turbulence is. CS are not the panacea they were initially presumed to be, nor are they as simple as we all had hoped. Despite some progress through CS research, the secrets of turbulence remain ever impenetrable.