报告题目：Assessing the capacity of turbulent flows to conduct geomorphic work

报告人：Manousos Valyrakis 博士，英国格拉斯哥大学

邀请人：曹志先 教授

时间：2018年8月30日（星期四）上午10:00

地点：国家重点实验室学术报告厅（农水楼一楼）

报告人简介：

     获希腊Aristotle University of Thessaloniki土木工程荣誉学位和土木环境工程硕士学位、美国Virginia Tech大学哲学博士学位； 现任英国University of Glasgow大学工学院讲师、水工程实验室主任；曾经在Science上发表关于泥沙起动临界条件的研究成果。

学术报告摘要：

       Knowledge of such near critical flow conditions is important for a variety of applications ranging from environmental hydraulics (such as protection of hydraulic structures from scour) to stream ecology, with regard to the assessment of the ecologically and environmentally sound flow conditions for the protection of stream habitat. Recently introduced theoretical concepts as well as probabilistic modeling approaches are presented. At near incipient flow conditions the magnitude of energetic flow events follows a power law distribution, over a wide range of frequencies, similar to many other geophysical phenomena. This implies that highly energetic flow structures, which have a good potential of impinging on an exposed particle and displacing it downstream, occur less frequently for the same low mobility flow conditions. This is in agreement with the intermittent and episodic character of particle entrainment observed from mobile particle flume experiments at low mobility flows. However, small changes in the mean flow or bed shear stresses may result in significant changes in the distribution of these flow structures. Further, analysis of synchronous time series of particle entrainment and local instantaneous flow upstream of it, allows for extraction and characterization of the scales and magnitudes that are relevant to the displacement of individual particles. In addition to having a sound theoretical basis, the stochastic modeling approach is shown to perform well in defining the condition of incipient motion and more generally the various levels of probability for particle entrainment.

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