時間：12月17日(四) 13：20
題目：The emergence of collective modes, ecological collapse and directed percolation at the laminar-turbulent transition
講者：施宏燕 研究員
服務單位：中央研究院 物理研究所
地點：本校科學三館1樓 110室
對象：本所博士生及碩士生、或其他有興趣之師生
摘要：
How a laminar flow becomes turbulence has been an unsolved problem for more than a century and is important in various industrial applications. Recently precise measurements in pipe flow experiments showed non-trivial spatiotemporal complexity at the onset of turbulence where lifetime and splitting time of metastable turbulence do not diverge asymptotically as would have been expected in a sharp transition.
Based on numerical evidence from the hydrodynamics equations, we discovered the surprising fact that the fluid behavior at the transition is governed by the emergent predator-prey dynamics of the important long-wavelength mode, leading to the mathematical prediction that the laminar-turbulent transition is analogous to an ecosystem on the edge of extinction. This prediction demonstrates that the laminar-turbulent transition is a non-equilibrium phase transition in the directed percolation universality class, and provides a unified picture of transition to turbulence emerging in systems ranging from turbulent convection to magnetohydrodynamics.
Reference:
[1] Hong-Yan Shih, Tsung-Lin Hsieh and Nigel Goldenfeld, Nature Physics 12, 245 (2016)
[2] https://www.nature.com/collections/rxsztdqblr
