首页 | 学院概况 | 师资队伍 | 本科生教育 | 研究生教育 | 科学研究 | 交流合作 | 党建工作 | 学生天地 | 工会视窗 | 校友之声 | 院务公开 
交流合作
 国内交流合作 
 国际交流合作 
 青年学术论坛 
首页>>交流合作>>青年学术论坛>>正文
航空学院青年学术论坛第五十讲(共三次报告)
2016-12-02 14:11   审核人:

报告人:

   加拿大西安大略大学机械工程与材料系系主任Jerzy M. Floryan教授,第24届国际理论与应用力学大会主席,德国洪堡科研奖获得者

报告一

报告题目:Effect of Distributed Surface Roughness on the Laminar-Turbulent Transition

时间:2016129日(星期五) 9:00-10:00

地点:友谊校区航空楼A706

报告摘要:

It has been recognized since the pioneering experiments of Reynolds in 1883 that surface roughness plays a significant role in the dynamics of shear layers. This is a classical problem in fluid dynamics but, nevertheless, its resolution is still lacking. Most of the efforts have been focused on experimental approaches that have resulted in a number of correlations but have failed to uncover the mechanisms responsible for the flow response. Theoretical analyses have also failed to provide a consistent explanation of the flow dynamics. As there are an uncountable number of possible geometrical roughness forms, the problem formulation represents a logical contradiction as it might not be possible to find a general answer to a problem that has an uncountable number of variations. The recent progress towards the theoretical resolution of this apparent contradiction will be discussed and recent results dealing with the problem of distributed surface roughness will be presented. The progress has hinged on the development of the immersed boundary conditions method and the reduced geometry concept. It will be shown that it is possible to propose a rational definition of a hydraulically smooth surface by invoking flow bifurcations associated with the presence of roughness. Successful resolution of roughness problems gives access to the design of surface roughness for passive flow control where drag reduction can be achieved either directly, through re-arrangement of the form of the flow that results in the reduction of the shear stress, or indirectly, through delay of the laminar-turbulent transition.

报告二

报告题目:On the Structured Convection

时间:2016年12月9日(星期五)14:30-15:30

地点:友谊校区航空楼A706

报告摘要:

Term“Structured Convection”refers to natural convection driven by patterns of heating. This convection is different from the classical Rayleigh-Bénard convection as it occurs regardless of the heating intensity as well as regardless of the position of the heating sources. Fluid movement is driven by density gradients but prediction of the system response is complicated due to spatial parametric resonance effects. A review of the recent results will be presented, primarily from the point of view of drag reduction associated with such convection. The relevant information can be found in the references given below.

“Drag Reduction in a Thermally Modulated Channel”, M.Z. Hossain and J.M. Floryan.  J. Fluid Mech., v. 791, 2016, pp. 122-153.

“Natural Convection in a Horizontal Fluid Layer Periodically Heated from Above and Below” by M. Z. Hossain and J.M. Floryan. Phys. Rev. E 92, 023015 (2015) 

"Mixed Convection in a Periodically Heated Channel", M,Z. Hossain and J.M. Floryan. J. Fluid Mech., vol. 768, 2015, pp. 51-90.

“Drag Reduction in Heated Channels”, Daniel Floryan and J.M. Floryan, J. Fluid Mech., vol. 765, 2015, pp. 353-395.

“Natural Convection in a Fluid Layer Periodically Heated from Above”, M.Z. Hossain and J.M. Floryan.  Physical Review E 90, 023015 (2014).

"Instabilities of Natural Convection in a Periodically Heated Layer", M. Z. Hossain& J. M. Floryan. J. Fluid Mech., 2013, v. 733, pp. 33-67.

"Drag Reduction due to Spatial Thermal Modulations", M.Z. Hossain, D. Floryan and J.M. Floryan, J. Fluid Mech., 2012, v. 713, pp. 398-419.

报告三

报告题目:Induced Polarization Effects in Liquid Droplets

时间:2016年12月12日(星期一) 9:00-10:00

地点:友谊校区航空楼A706

报告摘要:

It is desired in the production of sprays to find the ways to control the size and distribution of liquid droplets. It is also of interest to provide means for directing the spray towards the target of interest. Both these goals can be addressed using electric fields, e.g., electrostatic spraying/painting. The proper design and efficiency of these techniques rely on the understanding of the fundamental aspects of droplet dynamics when exposed to external electric fields, and especially on the understanding of the processes associated with droplet break up. This study is focused on the dynamics of liquid droplets driven by induced polarization effect and involves both experiments and theory. During experiments droplets were isolated from all other effects using microgravity environment. The evolution of droplets was captured using a high-speed movie camera. Theoretical analysis, which involved numerical simulation of the deforming droplet, was able to reproduce various stages of the deformation process in time up to the formation of Taylor cones. The droplet evolution process can be divided into rapid distortion followed by a combination of capillary instability and formation of Taylor cones and mass removal from the zone of the cones. Good agreement between the experiment and theoretical modeling has been observed. 

关闭窗口
版权所有©西北工业大学航空学院 | http://hangkong.nwpu.edu.cn