As you can see from the attached diagram, the particles are concentrated in the nodal planes at 0.008 s. But at 0.1s, the particles are not as concentrated in the nodal planes as at 0.008 s ( i.e. There are no red colours, just replace these red colours with yellow). Why are the suspended particles become less concentrated in the nodal planes as time goes by?
This is the manipulation of suspended solid particles using an ultrasonic standing wave field. The report that I attached is the brief report written from COMSOL Simulation V5.2
One possibiliy: The frequency drifts away from the resonance point. If it's a real experiment, the particles change the resonate frequency. Try again with a smaller number of particles or different mass.
Gathering in the field of standing waves happens with consolidation to some critical state - critical density, follows lowering of density.
Resonant frequency of a separate particle differs from the resonant frequency of the particles grouped till critical density.
Dear Nora Vilchinska and Herbert Weidner,
May I have your references? I found this information very new. It might help with my thesis
My recomendation is : look in rus.acad .Ganijev R. researches in granular matearal response to vibration (from Google)
I have just realized that the particles are concentrated at a period of time and then become less concentrated again, and then becomes concentrated again. It goes on and off. Hmm, perhaps it is because I did not add a gravitational force that would sediment these particles?
Because in reality, if I were to do an experiment, the acoustic radiation force will be greater than the gravitational force hence they will move these particles together in nodal or antinodal planes of the standing wave field. Once they are being clustered together, then gravitational forces play an important role. From there, sedimentation occurs. Do you agree with my statement?
But I am not sure why the particles are getting clustered and unclustered and then become clustered again, on and off for a set of period of time.
When the concentration changes periodically, there is a beat. This always requires two very close frequencies. One is determined by the generator. The other frequency is the resonance of the membrane. This varies, depending on where how many particles are.
https://en.wikipedia.org/wiki/Beat_%28acoustics%29
Interesting answer Herbert Weidner.
However, I am only using a frequency of 2 MHz because that is the resonant frequency. Does beating still occurs even if I use one frequency?
Or does the beating occured due to the difference in frequency between the transducer and the resonance of the suspended particles in the water?
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