Ullmann T, Schmid B, Manz P, van Milligen B, Tovar GEM, Ramisch M. Experimental observation of resonance manifold shrinking under zonal flow shear.
Phys Rev E 2020;
102:063201. [PMID:
33466072 DOI:
10.1103/physreve.102.063201]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 10/20/2020] [Indexed: 06/12/2023]
Abstract
In two-dimensional turbulent systems the redistribution of energy can be described by quadratic nonlinear three-wave interactions, which are limited by resonance conditions. The set of coupling modes can be understood as resonant manifold. It has been predicted by theory that, in the presence of a shear flow, the resonant manifold in wave-number space shrinks in time favoring large-scale structures. The phenomenon of manifold shrinking in the presence of shear flows is studied the first time experimentally in drift wave turbulence at the stellarator TJ-K by bicoherence analysis. By estimating effective mode numbers characterizing the width of the manifold, it is demonstrated that increasing shear leads to a shrinking of the resonance manifold.
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