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SUMMARY:A large-eddy pathway to turbulent drag reduction at high Reynolds 
 numbers - Ivan Marusic (University of Melbourne)
DTSTART:20220329T090000Z
DTEND:20220329T093000Z
UID:TALK171152@talks.cam.ac.uk
DESCRIPTION:Spanwise surface oscillation has been shown to be an effective
  drag reduction strategy for wall-bounded turbulent flows at low to modest
  Reynolds numbers (friction Reynolds numbers up to 1\,000). Here\, we pres
 ent experimental measurements of substantial drag reduction at friction Re
 ynolds numbers up to 12\,800 using spanwise surface oscillations. The drag
  reduction was measured via a combination of drag balance and hot-wire ane
 mometry. The drag reduction was found to occur via two distinct physical p
 athways. The first pathway\, recognised from previous studies\, involved a
 ctuating the surface at high frequencies\, comparable to those of the smal
 l-scale eddies that dominate turbulence near the surface. The second pathw
 ay\, however\, was new and leveraged actuation at low frequencies comparab
 le to those of the large-scale eddies farther from the surface. Importantl
 y\, this is accompanied with net-power savings due to the low actuation fr
 equencies used. Insights into the underlying mechanism for the drag reduct
 ion will be discussed.
LOCATION:Seminar Room 1\, Newton Institute
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