Swimming and pumping by helical waves in viscous and viscoelastic fluids

摘要: We study helical bodies of arbitrary cross-sectional profile as they swim or transport fluid by the passage waves. Many cases are explored: external flow problem swimming in a cylindrical tube an infinite domain, internal pumping problem, and confined/unconfined viscoelastic (Oldroyd-B) fluid. A coordinate system allows for analytical calculation speeds velocities asymptotic regime nearly bodies. In Newtonian flow, matched analysis results corrections to speed accurate fourth-order small wave amplitude, compare favorably with full numerical simulations. find that torque-balancing rigid body rotation generally opposes direction passage, but not always. Confinement can result local maxima minima pitch, effects confinement decrease exponentially fast diameter tube. fluid, we elasticity on modify through mode-dependent complex viscosity, even confined domain.