Tuesday, March 05, 2019
Been done before
Via Eurekalert, a study on agglomerating particles with sound waves.
One unique aspect of the experiments is that the sound not only levitates the particles, but can also be used to affect how they interact as they float. "A surprise was that by changing the sound wave frequency, we could manipulate the clusters and influence the shape that emerged," said graduate student Melody Lim, the first author on the paper. Modeling the physics behind such acoustic forces, which was done by Souslov and professor of physics Vincenzo Vitelli, gives scientists a new means to control the assembly process.At Penn State in the '80s I was a technical helper on Gerhard Reethof's experiments with agglomerating coal particles. The goal was to achieve better dust control by 'gluing' fine dust together into bigger globs that would fall out naturally. The experimental setup was complex and expensive, and the work stopped without a real conclusion when its sponsor Aerojet General got LBO'd and lost interest in the subject. After the end I noticed one peculiarity. We knew the modes and resonances of the cylindrical chamber (simulating a coal-fired boiler), so we had learned to pick the best resonances to get the best results. But there was one precise frequency, nowhere near a resonance, where the agglomeration reached a SHARP peak. IIRC it was around 940 cps. I tried to call this to the attention of the boss, but he wasn't interested. One of the grad students did a quick calculation and found that it corresponded to a characteristic vibration of the carbon atom, but I'm not sure if that was right. I wasn't interested either, so didn't pursue the subject.
Labels: Asked and badly answered
¶ 3:22 PM
