POSTER

(1)

Subcritical transition to turbulence in wall-bounded flows:

the case of plane Poiseuille flow

Paul Manneville

¹

& Masaki Shimizu

²

1Hydrodynamics Laboratory, CNRS-UMR7646, ´Ecole Polytechnique, Palaiseau, 91128 France

2Graduate School of Engineering Science, Osaka University, Toyonaka, 560-0043 Japan

plane Poiseuille flow driven by a pressure gradient

–

numerical simulations, program by M.S. (NIFS’s FUJITSU FX100 “Plasma Simulator” ) – wide domain 500×2×250 (also 1000×2×500 and 250×2×125)

– long durations, statistical steady state

R = 850 R = 1200 R= 1800 R = 3000 R = 4000

global stability for R < R_g ≈ 700 transitional regime with laminar-turbulent texture for R. R_t ≈ 4000; essentially “featureless” for R_t < R

(2)

•

_{decay at} R_g ❀ directed percolation (Sano &Tamai, 2016) ??? ❀ truncated scenario

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our article: arXiv:1808.06479 [physics.flu-dyn]

•

transition at R_t ❀ emergence of pattern at decreasing R ⇒ Fourier analysis (preliminary, ∃R_t ?)

2500 3000 3500 4000 4500 5000 5500

10¹ 10² 10³ 10⁴ 10⁵

maximum of spectral amplitude

R

Rt

2500 3000 3500 4000 4500 5000 5500

0.0 0.1 0.2 0.3 0.4

kz

kx

R

k

x

max

, k

z max