Behavior of active filaments near solid-boundary under linear shear flow

Abstract

The steady-state behavior of a dilute suspension of self-propelled filaments confined between planar walls subjected to the Couette-flow is reported herein. The effect of hydrodynamics has been taken into account using a mesoscale simulation approach. We present a detailed analysis of positional and angular probability distributions of filaments with varying propulsive force and shear-flow. Distribution of centre-of-mass of the filament shows adsorption near the surfaces, which diminishes with the flow. The excess density of filaments decreases with Weissenberg number as $Wi^{-\beta}$ with an exponent $\beta \approx 0.8$, in the intermediate shear range ($1 < Wi < 30$). The angular orientational moment also decreases near the wall as $Wi^{-\delta}$ with $\delta \approx 1/5$; the variation in orientational moment near the wall is relatively slower than the bulk. It shows a strong dependence on the propulsive force near the wall, and it varies as $Pe^{-1/3}$ for large $Pe\ge 1$. The active filament shows orientational preference with flow near the surfaces, which splits into upstream and downstream swimming. The population splitting from a unimodal (propulsive force dominated regime) to bimodal phase (shear dominated regime) is identified in the parameter space of propulsive force and shear flow.