报告一：Capillary rogue waves and the roles of modulation instability 

报告人：Prof. Michael Shats

报告二：Spectrally condensed turbulence 

报告人：Dr. Hua Xia

时 间：6月10日(周五)下午3:0
地 点：力学楼434会议室
主持人：佘振苏（教授）

报告一内容摘要：
    In this talk I will present results of recent studies of surface capillary waves. Capillary waves represent a high-frequency branch of surface waves in which the role of returning force is played by the surface tension (less than ~10mm). These weakly nonlinear and strongly dispersive waves show many features found in other waves systems in optics, magnetics, oceanic waves, etc. Of a particular importance is the modulation instability which is a four-wave process which appears to be responsible for a variety of capillary wave phenomena. Nonlinear spectral broadening and transitions to broadband wave turbulence are discussed along with a new effect, the generation of capillary rogue waves. These extreme events on the water surface are also related to modulation instability of capillary waves.

报告人简介：
     Prof. Michael Shats leads the Physics of Fluids Laboratory, Research School of Physics and Engineering, The Australian National University. Research areas: turbulence in fluids and plasma, nonlinear waves and surface wave turbulence, diffusion and transport of energy and particles.

报告二内容摘要：
     Recent experimental studies of turbulence in fluid layers are overviewed. Turbulence is electromagnetically forced in layers of electrolyte. Horizontal statistics of velocity fluctuations is affected by the bottom drag and by the presence of boundaries. When damping is sufficiently low, spectral energy starts accumulating at the scale of the boundary box leading to the formation of a spectral condensate, or a flow coherent across the entire domain. The flow interacts with the underlying turbulence and is fed by it via the inverse energy cascade. Such a state appears to be robust and has been studied in detail. In experiments in thick fluid layers with substantial 3D motions at low dissipation, a spectral condensate forms through a self-organization process. The condensate shears off vertical eddies in the layer leading to the flow planarization, facilitates an inverse energy cascade and reinforces itself. These new results have several important implications for the interpretation of the atmospheric wind data in troposphere and lower stratosphere.

报告人简介：
    Dr Hua Xia obtained her PhD at the Australian National University in 2006. After completing her thesis on turbulence in magnetized plasma and fluids, she moved to fundamental research in fluid dynamics. Her current research interests include statistical methods in turbulence in fluid layers, nonlinear waves and surface wave turbulence.