Principle of the rotation of small particles around a nodal point of strip in flexural vibration

In this report, we investigate the principle of rotation of micro particles around a nodal point of metal strip in flexural vibration, by experimental measurement and theoretical analysis. It is experimentally found that local travelling waves with the same travelling direction may exist along the circles centered at the nodal point of flexural vibration, and these local travelling waves can drive a particle cluster agglomerated at the nodal point to rotate. The acoustic radiation force, acoustic viscous force and acoustic streaming are excluded from the possible driving force by measuring and comparing the revolution speed of particle cluster in the normal environment of 1 atm and 25 °C and in a glass vessel of 0.04 atm and 25 °C. The generation of local travelling waves is related to the non-uniformity of vibration distribution along the width direction of vibration excitation part of metal strip. The physical principle obtained can well explain the measured relationships between the revolution speed and rotating particle number, and between the revolution speed and vibration displacement amplitude. There is slip between the rotating particles and vibrating surface, and air drag has little contribution to the particle rotation.