Ubertone's selection of acoustic tracers for laboratory setups

Tracers are essential

The acoustic profiling method needs scatterers that follow exactly the stream motion.

In some situations water may be naturally contaminated by dust or the flow loop can include a waterfall that generates microbubbles. In both cases, there may be enough scatterers to generate a significant echo for velocity measurement. If the echo signal is too weak, when measuring in clear liquid for example, it is necessary to add seeding particles (see picture on the right, Ubertone’s particles selection).

Furthermore, when studying acoustic turbidity, it is useful to have known particles as a reference.

Choosing the right particles

The choice of the right tracer can be crucial to the successful acquisition of experimental data. The particles should have :

  • a low Stokes number so that the particles follow the fluid streamlines,
  • an acoustic impedance that is sufficiently different from that of the liquid and
  • a size that is big enough compared to the wavelength so that the particles can be “seen” by the acoustic wave.

Ubertone has selected and characterised polyamide particles which fit perfectly to our devices and transducers. These particles can also be used for PIV and LDV techniques.

Ubertone’s particles specifications

With a diameter between 30 and 50µm (particle size analyzer: Beckman-Coulter LS13320), Ubertone’s particles present a very narrow size distribution with a gaussian shape.

The density of 1.01 is very close to water and leads to a very low settling velocity of 0.03 mm/s. This value has been calculated for water and validated experimentally.

This allows the particles to follow the fluid streamlines perfectly and to stay suspended for hours even in still water.

Polyamide particles
Mean particle size 40 µm +/- 2 µm
Size distribution D10 = 30 µm; D90 = 49 µm
Particle shape round but non-spherical
Density 1.01
Settling velocity 0.03 mm/s
Color white
Melting point 180°C
Pressure resistance High pressure resistant
Chemical resistance
  • alkaline, hydrocarbons, oils, gazoline's and solvents
  • attacked by acids

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A small concentration is enough

Only a small concentration of particles is needed to obtain a good echo. Typically, 50 mg/L is enough, but this concentration depends on the emitting frequency and the expected exploration depth.

Please keep environment safe !

Even though these polyamide particles a chemically non-reactive with the environment, these are not natural particles. It is not to be used in installations where the fluid is rejected directly in the environment or in the sewers. If you want to clear the fluid, you will have to filter it.

Ubertone fournit des traceurs en polyamide permettant d'améliorer la qualité des mesures de vitesse dans les liquides purs.

Généralement les impuretés ainsi que les micro-bulles générées par une chute d'eau suffisent à obtenir un écho acoustique. Cependant dans certains cas comme dans l'eau ou l'huile pure par exemple, l'ajout de particules traceurs permet d'obtenir un signal Doppler.