Hi Luca,

I found a thesis on acoustophoresis. It had this graphic for the frequency range of interest in blue:

I did a "back of the envelope" calculation to scope out the maximum element size for acoustic models.

Assume your maximum frequency, f, is 10 MHz. The speed of sound, c, in water is about 1500 m/s.

Let's calculate the wavelength of a 10 MHz sound in water: lambda = c/f = 1500/10^7 = 0.00015 m or 0.15 mm.

At least 6 quadratic elements are needed along one wavelength to adequately represent the wave. That means the maximum element size in the model would be 0.025 mm for 10 MHz.

I hope your domain is very small if that is your maximum element size. If your domain is 5 cubic mm, then you will need 200 elements on a side or 8 million elements. That is a big model. If your domain is 10 cubic mm, then you will need 400 elements on a side or 64 million elements, which is not feasible.

You can redo the calculations for your maximum frequency, if it is < 1 MHz the model size becomes more reasonable.

Regards,

Peter