BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Linear dynamics in turbulent flows over a porous layers - Nabil Ab
 derrahaman-Elena
DTSTART:20141205T130000Z
DTEND:20141205T140000Z
UID:TALK55525@talks.cam.ac.uk
CONTACT:Aleksandra Przydrozna
DESCRIPTION:The reduction of skin friction in turbulent flows has been an 
 active area of research for several decades. Surface geometry manipulation
 s have been studied thoroughly as a form of passive flow control to reduce
  viscous drag. A few techniques\, such as surface riblets and superhydroph
 obic surfaces have been shown to produce drag reduction.\n\nHere we propos
 e the use of anisotropically-porous coatings to reduce skin friction. Poro
 us surfaces can produce an effectively slip for the overlying\, turbulent 
 flow. If the permeability of the porous layer is anisotropic\, the apparen
 t slip depends on the orientation of the flow with respect to the surface.
  The theoretical analyses of Luchini et al. \n(1991) and Jimenez (1994) pr
 edict that the drag reduction is proportional to the difference between sl
 ips. However\, this proportional trend begins to degrade for a given size\
 , beyond which the performance ceases to improve\, and the surface treatme
 nt is no longer interesting from an application perspective. This degradat
 ion occurs when Kelvin--Helmholtz-like spanwise rollers begin to develop o
 ver the surface. These rollers generate additional Reynolds stresses\, whi
 ch are responsible for the degradation of drag.\n\nBased on the above conc
 epts of anisotropic slip length and onset of a Kelvin--Helmholtz-like inst
 ability\, we aim to obtain estimates for the parameters that maximize the 
 drag reduction produced by a coating with anisotropic porosity.\n
LOCATION:LR3B\, Inglis Building\, CUED.
END:VEVENT
END:VCALENDAR