title: Speed of a swimming sheet in Newtonian and viscoelastic fluids.
abstract: We measure the swimming speed of a cylindrical version of Taylor's swimming sheet in viscoelastic fluids, and find that depending on the rheology, the speed can either increase or decrease relative to the speed in a Newtonian viscous fluid. The swimming stroke of the sheet is a prescribed propagating wave that travels along the sheet in the azimuthal direction. The measurements are performed with the sheet immersed in a fluid inside a cylindrical tank under torque-free conditions. Swimming speeds in the Newtonian case are found to be consistent with calculations using the Stokes equation. A faster swimming speed is found in a viscoelastic fluid that has a viscosity independent of shear rate. By contrast, a slower swimming speed is found with more complex shear-thinning viscoelastic fluids which have multiple relaxation time scales as well. These results are compared with calculations with Oldroyd-B fluids which find a decreasing swimming speed with Deborah number given by the product of the fluid elastic relaxation time scale and the driving frequency.
authors: Department of Physics, Clark University, Worcester, Massachusetts 01610, USA.
authors: Moumita
authors: M
authors: Dasgupta
authors: Bin
authors: B
authors: Liu
authors: Henry C
authors: HC
authors: Fu
authors: Michael
authors: M
authors: Berhanu
authors: Kenneth S
authors: KS
authors: Breuer
authors: Thomas R
authors: TR
authors: Powers
authors: Arshad
authors: A
authors: Kudrolli
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D055119:Elastic Modulus; D008962:Models, Theoretical; D012212:Rheology / Q000379:methods*; D013550:Swimming; D014783:Viscosity