Ultrasonic imaging of small particles in oil

Undergraduate student Matheus A. Burda and post-doctoral resident Tatiana A. Prado are working on the ultrasonic imaging of very small particles. That routine produces very peculiar photos such as the one below.

In the picture, a 64-element array transducer is peering into some mineral oil to “see” the particles. In this case, the particles are small pieces of polyethylene with an average diameter of 200µm. These particles are representative of early formations of hydrates, which occur in oil production facilities and are strongly undesirable (therefore, early detection would be very useful). This transducer was built for LASSIP by French company Imasonic and can withstand pressures up to 200 bar, which makes it suitable for subsea environments.

The center frequency of the transducer is 5MHz. Considering the very famous v = λf equation and that the sound speed in mineral oil is around v = 1500m/s, we expected the imaging system to be able to have a resolution of approximately λ = f/v = 300µm according to the Rayleigh criterion. So, yes, most of the particles should be visible.

And indeed they are. The time-lapse shown below was created by Matheus from shots taken at 5-second intervals. The images were generated from the data using the Total Focusing Method algorithm, which is a state-of-the-art method in terms of resolution.

Our Python implementation of the TFM algorithm will soon be available in a JupyterLite project that is being developed by the part of our team hosted at campus Pato Branco of UTFPR and led by Prof. Giovanni A. Guarneri.

In case you liked the topic, you can check Matheus’ and Tatiana’s detailed report here.