BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Turbulence over rough/textured walls does not obey Navier-Stokes e
 quations - Ricardo Garcia-Mayoral (University of Cambridge)
DTSTART:20220401T083000Z
DTEND:20220401T090000Z
UID:TALK171224@talks.cam.ac.uk
DESCRIPTION:This talk will discuss the effect of surface texture on the ov
 erlying turbulence. For very small textures\, turbulence remains smooth-wa
 ll-like\, and the only effect is an apparent origin offset for different f
 low components\, which results in a drag increase or reduction through a c
 hange in the so-called 'roughness function'. In this regime\, the texture 
 can be replaced by equivalent\, homogeneous boundary conditions\, and thus
  the change in drag can be predicted a priori. Unfortunately\, this regime
  breaks down once the texture size becomes comparable to the smallest leng
 thscale in the overlying flow (typically 15 wall units) so its practical r
 elevance is limited. Beyond this regime\, drag predictions often resort to
  correlations for known textures\, overlooking that 'roughness' is a hydro
 dynamic property\, so it is not difficult to find examples of surfaces for
  which existing correlations do not work. Instead\, we focus on understand
 ing the mechanisms through which the dynamics of the overlying turbulence 
 are modified by the texture. As a first step in this direction\, we focus 
 on the effect of slip/no-slip textures - a popular model for superhydropho
 bic surfaces - which make the problem particularly simple. For these textu
 res\, effective homogeneous boundary conditions can be shown to hold for s
 izes much larger than 15 wall units. However\, for larger sizes\, the text
 ure-coherent flow interacts directly with the background turbulence and mo
 difies its equations of motion\, which are no longer Navier-Stokes'. We pr
 ovide evidence for this comparing texture-resolved simulations and texture
 -less simulations with homogeneous boundary conditions and modified govern
 ing equations.
LOCATION:Seminar Room 1\, Newton Institute
END:VEVENT
END:VCALENDAR