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aries1988 : fluid   13







2007年,陶哲轩写了一篇文章名为“Why global regularity for Navier-Stokes is hard”的博客。在这篇文章中,他认为求解类似NS方程这种的偏微分方程组就像寻找一个大尺度的定量的可以模化的特性,来对不可以预测的行为进行限定。


fluid  mechanics  explained  maths  research 
december 2017 by aries1988
V0088: Turning on a Dime – Asymmetric Vortex Formation in Hummingbird Maneuvering
Hummingbirds are versatile natural flyers that can perform locomotion as insects, such as hovering, forward/backward flight, turning maneuver and more. The unsteady vortex dynamics is key to understand aerodynamic features of these motions. Here we present an integrated approach combining high-speed photogrammetry, wing/body surface tracking, and immersed boundary method based flow simulations to study the three-dimensional vortex dynamics of a freely maneuvering hummingbird. The simulation results of the hummingbird performing pure yaw turn show asymmetric wake structures between the inner and outer wings. Dual-loop vortex structures have been observed in the near wake of the outer wing during downstroke, and of the inner wing during upstroke. The interactions between the wings and these complex vortex structures have implied both aerodynamic and dynamic benefits of the flapping wings in hummingbird’s maneuvering flight. (This work is supported by NSF CBET-1313217 and AFOSR FA9550-12-1-0071)
bird  cfd  fluid  visualization 
january 2016 by aries1988
The Singular Mind of Terry Tao
in the process, he will have also solved the Navier-­Stokes global regularity problem, which has become, since it emerged more than a century ago, one of the most important in all of mathematics.

‘‘A very central part of any mathematician’s life is this sense of connection to other minds, alive today and going back to Pythagoras,’’ said Steven Strogatz, a professor of mathematics at Cornell University. ‘‘We are having this conversation with each other going over the millennia.’’

Long ago, mathematicians invented a number that when multiplied by itself equals negative 1, an idea that seemed to break the basic rules of multiplication. It was so far outside what mathematicians were doing at the time that they called it ‘‘imaginary.’’ Yet imaginary numbers proved a powerful invention, and modern physics and engineering could not function without them.
maths  idea  fluid 
august 2015 by aries1988

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