Berlin 2018 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 27: Microfluidics

DY 27.3: Talk

Tuesday, March 13, 2018, 11:45–12:00, BH-N 128

Particle interactions in inertial microfluidics — •Christian Schaaf, Felix Rühle, and Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, Berlin, Germany

Solid particles immersed in a microfluidic Poiseuille flow at intermediate Reynolds numbers migrate laterally to discrete equilibrium positions [1]. This Segré-Silberberg effect can be explained by the inhomogeneous shear rate of the Poiseuille flow and can be rationalized by the lift force profile. In addition to this lateral inertial focusing, particles at low densities also form regular particle trains in the direction of the flow [2].

We conduct lattice-Boltzmann simulations to obtain some understanding for the formation of such structures. As a first step we focus on the dynamics of a flowing particle pair. We determine their lift force profiles as function of the lateral particle positions and axial distance as well as the Reynolds number. At small distances the profiles are dominated by viscous forces, while at large distances inertial forces take over. Additionally, we categorize the different types of trajectories and show how particles in the bound state spiral towards their equilibrium positions performing damped oscillations. In the end these results are used to explain the behavior of particle trains and to analyze their dynamics and stability.

[1] G. Segré and A. Silberberg, Nature 189, 209 (1961).

[2] W. Lee, et al., PNAS 107, 22413 (2010).

[3] C. Schaaf and H. Stark, submitted.