Lateral force on a rigid sphere in large-inertia laminar pipe flow

We present a prediction of the lateral force exerted on a rigid neutrally buoyant sphere in circular cross-section Poiseuille flow. The force is calculated with the method of matched asymptotic expansions. We investigate the influence of the pipe Reynolds number in the range 1–2000 on the equilibrium position and the magnitude of the lateral force. We show that the predicted lift force in a circular geometry is qualitatively similar to, but quantitatively different from, that in a plane channel. The predicted force in the pipe is significantly smaller than the channel result, and the zero of the force which determines the equilibrium radial position of a suspended particle lies closer to the centreline in the pipe.