Ubertone provides optimal 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 scatterers
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.
See FAQ for more details.
Ubertone has selected and characterised polymer particles which fit perfectly to our devices and transducers. These particles can also be used for PIV and LDV techniques.
Another option consists in generating micro-bubbles, which are very efficient for some setups. The main advantage is the total eco-friendly aspect. One warning has thus to be noted when the flow conditions and transducer position are such as bubbles are accumulating on the active surface of the transducer, impacting greatly the measurement quality.
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.
Main particles characteristics:
|Mean particle size||40 µm +/- 2 µm|
|Size distribution||D10 = 30 µm; D90 = 49 µm|
|Particle shape||round but non-spherical|
|Settling velocity||0.03 mm/s|
|Pressure resistance||High pressure resistant|
|Chemical resistance||Resistant to alkaline, hydrocarbons, oils, gazoline's and solvents. Attacked by acids.|
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.
As an example: our particles, at a concentration of 100 mg/L, give a good signal at 3 MHz emission frequency, allowing an up to 50 cm deep profile measurement.
Please keep the environment safe !
Even though these polyamide particles are 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.