Greetings PFers, I'm working on a project where I need to focus powdered that is being blown through a tube. I would like to discuss the option of using acoustic focusing to guide the particles to the axis of the tube to prevent the particles from contacting the tube inside diameter. There is plenty of research on acoustic focusing on very small scales, but i'm interested in using a standard speaker to focus particles inside an 11mm ID cylinder instead of the traditional piezo element. I want to mount a acoustic waveguide perpendicular to the axis of the carrier gas and establish a standing wave where the node is aligned with the axis of the tube. The difficulty i'm having is calculating the amplitude of the wave necessary to move the X axis of the particle trajectory towards the axis of the tube. I appreciate any help I can get. kind regards.