MICRO FLUIDICS | ARTICLE The CFD Model
We developed CFD models in COMSOL Multiphysics to predict the equilibrium locations of the particles and their variation with flow and geometry parameters. To simplify the model and reduce solution time the analysis was divided into two steps. In the first step, we solve a CFD problem that does not include the particle. This gives the standard Hagen-Poiseuille flow solution for straight channels and the Dean flow solution for curved channels. We then map this solution to the inlet boundary of a second CFD model with the particle represented as a void in the CFD domain, with appropriate moving wall conditions to account for the translation and rotation of the particle. Both CFD models were parameterised to facilitate the investigation of the effect of flow and geometry parameters.
The reaction forces and moments on the particle are calculated from the CFD solution and are used to update the particle’s translational and rotational velocity components. To accomplish this, we set up global ordinary differential equations (ODEs) specifying the equilibrium of the particle in terms of its linear and angular velocities.
Originally discovered in 1960s, the phenomenon of inertial focusing found new utility in micro fluidics, and in particular biomedical device design, recently playing a key role in a device enabling the ability to detect cancer from a blood sample.
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