Self-propelled particles with torque trace circular paths near boundaries
Active particles (microswimmers like bacteria, Janus particles) self-propel at speed v₀ along their orientation θ, which rotates at angular velocity Ω (chirality). Near no-slip boundaries, hydrodynamic interactions trap swimmers in circular orbits. The model: ṙ = v₀(cos θ, sin θ), θ̇ = Ω + η(t), with rotational diffusion noise. Concentration near walls is a non-equilibrium effect with no passive analog.