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Some Remarks on the Removal of Adhered Particles by Oscillating Air Flows

On the background of technical concepts for the removal of particles from moving textiles by linear as well as oscillating air flows, some theoretical remarks on particle adhesion forces and the hydrodynamical and acoustic forces acting on particles are given. As the main removal forces in linear air flows, drag and lift are taken into consideration and analytical expression derived from the Bernoulli equation. For a hypothetical example of particles in the size range from below 0.5 to 7 μm on a cotton fiber, hydrodynamic forces are compared to van der Waals interaction, electrostatic forces and capillary forces. In this work, a special focus is placed on the application of high-frequency oscillating air flows which results in a direct coupling of ultrasound to the particles. The theoretical calculation of resulting forces showed that the detachment threshold is determined not only by sound intensity level, but also by the frequency of the ultrasonic wave. If capillary forces act, the coupling of ultrasound alone does not suffice to detach particles within the considered size range.