PHYSICS/BK21 SEMINA[09..07.03]

"            
           “Onsager Principle and
         Nanoscale Hydrodynamics”
  
♦Speaker :  Prof. Ping Sheng (Hong Kong University)  
♦Place : Physics Seminar Room (Science Bldg, 3-201)
♦Date & Time : July 3 (Fri), 15:00 ~ 16:00 pm  

Abstract
    
It is probably not a well-known fact that up until recently, continuum hydrodynamics can not accurately
model immiscible flows at the nanoscale.  The problem is not with the  Navier-Stokes  equation,  which
must be true, but lies in the hydrodynamic boundary condition, which for  the  past  century  has  been
held to be no-slip at the fluid-solid interface.  In this talk, the history  of  the  hydrodynamic  boundary
condition and its associated classic problem of moving contact line will be introduced in  some  detail.
Here the contact line denotes the intersection of the immiscible fluid-fluid interface with the solid wall,
and when one fluid displaces the other, the contact line moves along  the  solid  wall.   Almost  half  a
century ago it was already recognized that the moving contact line will lead to infinite viscous dissipation
if one uses the no-slip hydrodynamic boundary condition.  We show that by using the Onsager variational
principle, which can be easily derived from basic statistical mechanic principles, one can simultaneously
derive the Navier-Stokes equation  and  its  related  boundary  conditions  at  the  fluid-solid  interface.  
The resulting continuum hydrodynamic system, with the revised hydrodynamic  boundary  conditions,  is
shown for the first time to quantitatively reproduce molecular dynamic simulation results at the nanoscale.
Implications of this result for nanoscale hydrodynamics, together with its complementary relation to  the
kinetic theory of fluids, will be shown by short movies as well as discussed.
  
              Contact Person : Prof. Wokyung Sung(054-279-2061, wsung@postech.ac.kr)
              "