Lift forces of screws in shear flows

Abstract

We have measured the forces in the vorticity direction experienced by chiral screws in shear flows, with the Reynolds number at the order of 103. The measured force directions depend on the screw handedness, being in the positive vorticity direction for left-handed screws and opposite for right-handed ones. These directions are the reverse of those predicted in the low Reynolds number (Stokes flow) calculations [M. Makino and M. Doi, Phys. Fluids 17, 103605 (2005)]. The force magnitude scales with the cube of the shear rate and is about 100 dyn (on the order of 10% of the drag force) when the shear rate ∼ 10-1 S-1. © 2007 American Institute of Physics.