Abstract

We use direct numerical simulations in the presence of free-stream turbulence having different values of intensity, Tu, and integral length scale, L, in order to determine which kind of structures are involved in the path to transition of a boundary-layer flow. The main aim is to determine under which conditions the path to transition involves structures similar to the linear or non-linear optimal perturbations. For high values of Tu and L, we observe a large-amplitude path to transition characterized by localized vortical structures and patches of high- and low-momentum fluctuations. Such a scenario is found to correlate well with the Λ and hairpin structures resulting from the time evolution of non-linear optimal perturbations, whereas, for lower Tu and L, a larger correlation is found with respect to linear optimal disturbances. This indicates that a large-amplitude path to transition exists, different from the one characterized by elongated streaks undergoing secondary instability. To distinguish between the two transition scenarios, a simple parameter linked to the streamwise localisation of high- and low-momentum zones is introduced. Finally, an accurate law to predict the transition location is provided, taking into account both Tu and L, valid for both the transition scenarios.

Autore Pugliese

• De Palma Pietro

Tutti gli autori

• Cherubini S , Robinet J-C , De Palma P

Titolo volume/Rivista

ENERGY PROCEDIA

Anno di pubblicazione

2014

ISSN

1876-6102

ISBN

Non Disponibile

Numero di citazioni Wos

Nessuna citazione

Ultimo Aggiornamento Citazioni

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Numero di citazioni Scopus

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0

Ultimo Aggiornamento Citazioni

2017-04-22 03:20:59

Settori ERC

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Codici ASJC

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