The attached reverse and detached forward cascades in wall-turbulent flows

1st Multiflow Summer Workshop

Cimarelli, Andrea^1 ; De Angelis, Elisabetta^1 ; Talamelli, Alessandro^1 ; Casciola, Carlo Massimo^2 ; Jiménez, Javier^3

Dipartimento di Ingegneria Industriale, Università di Bologna, 47121 Forlì, Italy^1

Dipartimento di Ingegneria Meccanica e Aerospaziale, Università di Roma la Sapienza, 00185 Roma, Italy^2

School of Aeronautics, Universidad Politécnica de Madrid, Madrid 28040, Spain^3

关键词: Bulk flow;    Cascade mechanism;    Cascade process;    Large-scales;    Near-wall region;    Small scale;    Wall bounded turbulence;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/506/1/012005/pdf
DOI  :  10.1088/1742-6596/506/1/012005

来源: IOP

【 摘 要 】

The present work describes the multidimensional behaviour of wall-bounded turbulence in the space of cross-scales (spanwise and wall-normal) and distances from the wall. This approach allows us to understand the cascade mechanisms by which scale-energy is transmitted scale-by-scale away from the wall, through the overlap layer, and into the bulk flow. Two distinct cascades are identified involving the attached and detached scales of motion, respectively. From the near-wall region, scale-energy is transferred towards the bulk, flowing through the attached scales of motion, while among the detached scales it converges towards small scales, ascending again to the channel centre. It is then argued that the attached scales of wall-bounded turbulence are involved in a reverse cascade process that starts from the wall and ends in the bulk flow. On the other hand, the detached scales belong to a direct forward cascade process towards dissipation. Hence, at a given distance from the wall the attached motion is fed by smaller attached scales located closer to the wall. In turn this attached motion is responsible for creating the scale-energy that sustains larger attached scales farther from the wall and smaller detached scales that are responsible for connecting the scale-energy at large scales to the dissipation at small scales through a forward cascade.