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SUMMARY:Theory of margination in blood and other multicomponent suspension
 s - Michael D. Graham (University of Wisconsin-Madison)
DTSTART:20170222T130000Z
DTEND:20170222T140000Z
UID:TALK71101@talks.cam.ac.uk
CONTACT:Julius Bier Kirkegaard
DESCRIPTION:Blood is a suspension of objects of various shapes\, sizes and
  mechanical properties\, whose distribution during flow is important in ma
 ny contexts. Red blood cells tend to migrate toward the center of a blood 
 vessel\, leaving a cell-free layer at the vessel wall\, while white blood 
 cells and platelets are preferentially found near the walls\, a phenomenon
  called margination that is critical for the physiological responses of in
 flammation and hemostasis. Additionally\, drug delivery particles in the b
 loodstream also undergo margination – the influence of these phenomena o
 n the efficacy of such particles is unknown. \n\nIn this talk a mechanisti
 c theory is developed to describe segregation in blood and other confined 
 multicomponent suspensions. It incorporates the two key phenomena arising 
 in these systems at low Reynolds number: hydrodynamic pair collisions and 
 wall-induced migration. The theory predicts that the cell-free layer thick
 ness follows a master curve relating it in a specific way to confinement r
 atio and volume fraction. Results from experiments and detailed simulation
 s with different parameters (flexibility of different components in the su
 spension\, viscosity ratio\, confinement\, among others) collapse onto the
  same curve.  In simple shear flow\, several regimes of segregation arise\
 , depending on the value of a ``margination parameter'' M. Most importantl
 y\, there is a critical value of M below which a sharp ``drainage transiti
 on'' occurs:  one component is completely depleted from the bulk flow to t
 he vicinity of the walls. Direct simulations also exhibit this transition 
 as the size or flexibility ratio of the components changes. Results are pr
 esented for both Couette and plane Poiseuille flow. Experiments performed 
 in the laboratory of Wilbur Lam indicate the physiological and clinical im
 portance of these observations. 
LOCATION:MR11\, Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge
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