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In the presence of particles, the vorticies that result from the unstable perturbations offer interesting interactions with the suspended particles. In a general sense, "light" particles get trapped in the flow vorticies, while "heavier" particles carrying more inertia might get expelled under a centrifugal-type force from the swirling regions to gather along stretching regions of the flow [2,3]. This effect is known as preferential concentration and is illustrated in the following sketch:
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