Formation of a strong negative wake behind a helical swimmer in a viscoelastic fluid

We investigate the effects of helical swimmer shape (i.e., pitch angle and tail thickness) on swimming dynamics in a constant viscosity viscoelastic (Boger) fluid via combination particle tracking velocimetry, image velocimetry 3D simulations FENE-P model. The printed is actuated magnetic field using custom-built rotating Helmholtz coil. Our results indicate that increasing thickness enhances normalized speed ratio Boger to Newtonian fluid). Strikingly, unlike fluid, flow around characterized by formation front-back asymmetry strong negative wake downstream swimmer. Evidently, strength inversely proportional speed. Three-dimensional with model conditions match those experiments, confirm similar Finally, developing an approximate force balance streamwise direction, we show contribution polymer stresses interior region helix may provide mechanism for enhancement or diminution fluid.