北京大学湍流与复杂系统国家重点实验室-学术讲座

工学院力学系学术报告（报告人：Dr. Patrick Le Quéré）

发布时间: 2009-07-09 01:26:00　　

SEMINAR SERIES

北京大学工学院力学与空天技术系

湍流与复杂系统国家重点实验室

题目：About the computation of external or partially enclosed natural flows and some related issues

题目：

报告人 Dr. Patrick Le Quéré

Director of LIMSI-CNRS, France

报告内容摘要：

We address the issue of the computation of natural convection in external or partially enclosed domains, such as natural convection flow in vertical open channels or along heated vertical plates which raises the question of the proper choice of artificial boundary conditions and of their numerical implementation. To this aim we perform a singular value decomposition of the discrete Stokes operator that arises from the discretization of the governing Navier-Stokes equations, using the classical staggered grid formulation. We show that some choices of boundary conditions lead to an increase of the kernel of this operator making the solution of the full nonlinear equations indefinite. This arises in particular when Neumann type boundary conditions are imposed on the velocity component normal to the main inlet and outlet boundaries. The existence of one or more velocity-pressure combinations solutions of the homogeneous Stokes operator can be used to derive a superposition algorithm in which a linear combination of these modes is added to a particular solution of the nonlinear equations in order to satisfy given constraints such as a pressure condition for instance. For the simple geometrical configurations considered, the singular mode is easily identified, which allows to avoid the numerical computation of the exact full size discrete problem. Sample calculations are performed to demonstrate the effectiveness of this new algorithm, which has many applications in other configurations such as flows between rotating disks, or pipe flows with several outlets for instance.

报告人简介：

Dr. Patrick Le Quéré, director of CNRS-LIMSI. The LIMSI laboratory accommodates approximately 120 permanent personnel (researchers, professors and assistant professors, engineers, technicians) and about 60 PhD candidates. It undertakes multidisciplinary research in Mechanical and Chemical Engineering and in Sciences and Technologies for Information and Communication. The research fields cover a wide disciplinary spectrum from thermodynamics to cognition, encompassing fluid mechanics, energetics, acoustics and voice synthesis, spoken language and text processing, vision, virtual reality. . .

主持人：佘振苏教授

时间：7月16日（周四）下午3:30

地点：力学楼434会议室

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