Slip slender-body theory

Slip effects on solid boundaries are common in complex fluids. Boundary depletion layers in polymer solutions can create apparent slip effects, which can in turn significantly impact the dynamics of moving bodies. Motivated by microswimmer locomotion in such environments, we derive a series of slip slender-body theories for filamentous bodies experiencing slip-like boundary conditions. Using Navier’s slip model, we derive three slip slender-body theories, linking the body’s velocity to the distribution of hydrodynamic forces. The models are shown to be consistent with each other and with existing numerical computations. As the slip length increases, we show that the drag parallel to the body decreases towards zero while the perpendicular drag remains finite, in a manner which we quantify. This reduction in drag ratio is shown to be inversely related to microswimmer mobility in two simple swimmer models. This increase could help rationalise empirically observed enhanced swimming in complex fluids.