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SUMMARY:MEchanics GAthering -MEGA- Seminar: Fluid inertia and the scallop 
 theorem
DTSTART:20220303T161500
DTEND:20220303T173000
DTSTAMP:20260916T003932Z
UID:f39952bed9afa38bdcc4c52bb6c149c64814851e92686092cedaab83
CATEGORIES:Conferences - Seminars
DESCRIPTION:Nick Derr (Applied Mathematics\, Harvard University)\nAbstra
 ct In Stokes flow\, Purcell's scallop theorem forbids objects with time-r
 eversible (reciprocal) swimming strokes from moving. In the presence of in
 ertia\, this restriction is eased and reciprocally deforming bodies can sw
 im. Recent works have investigated an asymmetric spherical dimer of oscill
 ating length as a simple model swimmer. Analytical\, numerical\, and exper
 imental studies have shown a dense (i.e. inertial) dimer swims in Stokes f
 low. Similarly\, numerical study shows a dimer in fluid of intermediate Re
 ynolds number (Re = 1-1000) swims in a direction that varies depending on 
 the degree of fluid inertia\, but the reasons for this direction change ha
 ve not previously been elucidated. Here\, we introduce a general model fo
 r the inertial flow produced by an oscillating dimer at small amplitudes. 
 We apply the finite element method\, using the PETSc library to solve a co
 upled pair of linear PDEs\, to probe the dimer's swim speed with respect t
 o the degree of fluid or solid inertia. The results are compared to asympt
 otic solutions obtained via the method of reflections. We find the model's
  predictions match those of the dense Stokes swimmers in the appropriate l
 imit\, and that the behavior in inertial fluid is consistent with the prev
 iously observed switch in direction.\n\nBiography Nick Derr uses simplifi
 ed models and high-performance computation to study active systems in biol
 ogy and physics\, especially those with elements of poroelastic flow or fl
 uid-solid interaction. He received a BS from the University of Wisconsin 
 in 2015 and a MASt in Applied Math from the University of Cambridge in 201
 6. He is a PhD Candidate in Chris Rycroft’s group at Harvard University\
 , and will start as an Instructor in the MIT Math Department this summer.
LOCATION:MED 2 2423 https://plan.epfl.ch/?room==MED%202%202423 https://epf
 l.zoom.us/s/64863509346
STATUS:CONFIRMED
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