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SUMMARY:Statistical analysis of non-linearities in turbulence - Andre Cava
 lieri (Instituto Tecnológico de Aeronáutica)
DTSTART:20220330T103000Z
DTEND:20220330T110000Z
UID:TALK171185@talks.cam.ac.uk
DESCRIPTION:Recent years have seen significant progress in the analysis of
  coherent structures in turbulent flows via an input-output framework\, wh
 ere non-linear terms\, considered as "forcing"\, drive a flow response thr
 ough the resolvent operator\, obtained by a linearisation of the Navier-St
 okes system around the mean flow. This leads to models that often provide 
 a good approximation of dominant coherent turbulent structures as the flow
  responses with maximal amplification by the resolvent. However\, accurate
  quantitative agreement depends on the specific details of the forcing. In
  this presentation we will explore non-linear terms from simulations of tu
 rbulent channel flow and their connection to flow responses. The statistic
 s of such non-linear terms are seen to have low rank\, implying that coher
 ent structures are driven by non-linear interactions that are also coheren
 t\; this is in contrast with the usual white-noise forcing assumption in l
 inearised models. Non-linear terms are also seen to be approximately self-
 similar across a broad range of scales. Such properties provide directions
  to improve existing models of turbulent structures based on the linearise
 d operator\, and also to build accurate linear estimators for turbulent fl
 ows.
LOCATION:Seminar Room 1\, Newton Institute
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