Inertial particle impaction on a cylinder in turbulent cross-flow at modest Reynolds numbers

Abstract

Particle impaction on a cylinder in a cross-flow is investigated with the use of Direct Numerical Simulations, with focus on the effect of free-stream turbulence on the front-side impaction efficiency. The turbulence considered is high-intensity homogeneous isotropic turbulence, introduced upstream of the cylinder in moderate Reynolds number flows. It is found that the free-stream turbulence leads to a significant increase in the number of particles that impact the cylinder for certain Stokes numbers (St). The peak amplification of impaction is observed at St=0.3, for different integral scales and Reynolds numbers. This peak is related to a change in impaction mechanism, from boundary stopping to boundary interception, and it will therefore depend on the size of the particles as well as on the Stokes number. Using statistical analysis, an expectation value of predicted effects of free-stream turbulence on particle impaction is derived. This expression predicts the observed impaction amplification to a good degree, particularly in terms of which Stokes numbers that are affected by the turbulence.