Ice nucleation on soot particles

The present paper analyzes the coupling between particle temperature and drag force. The force was measured for heated and unheated particles of about a hundred micrometers in diameter suspended in an electrodynamic chamber. Particle temperature was up to several hundred degrees above room temperature. Horizontal flow velocities were in the range of 0-0.1ms-1, providing very low particle Reynolds numbers. It was found that due to free convection, the drag force acting on a heated particle can be several times greater than the corresponding force for a non-heated one. This effect is especially significant at low flow velocities and is suppressed as the velocity increases. The influence of particle diameter, temperature difference and flow velocity is investigated, clarifying the contribution of each parameter. The drag force applied to a heated particle is found to behave according to a Stokes-like expression, modified in order to take into account the effect of free convection.