Local void ratio
The local void ratio may be calculated on each channel by summing durations of logical slots corresponding to the probe being in the medium. The ratio of this sum to the total measurement time is the mean value of the local void fraction.

Local speed

Local speed is calculated through signals from a double probe oriented along the axis of the flow. The principle of determination consists in recognizing the coincidence of probe signals (the pairs of events corresponding the same bubble passing through both probes).

Interface area

If the stereology of the two-phase is isotropic the interface area may be calculated from the speed and frequency of the bubbles coming through, using the formula :

where fb is the frequency of the bubbles and Vb the velocity of the medium, these two values being obtained using a double probe. The software computes the mean value of the interface area during the sampling sequence.

Download ISO software documentation

Granulometry

The granulometry of the two-phase flow (ie : the bubble-size statistical distribution) may be computed from the probe signals assuming spherical bubbles.

As a double probe makes a measurement of any chord of randomly distributed bubbles, the restoration of actual diameters can be done through statistical considerations only. The calculation method is valid for the following hypotheses.

the bubbles are spherical,

the flux of bubbles is uniform and random in the section,

the instantaneous speed vector is close to the axis of the double probe (no angular effect on chord measurements),

the greater part of the bubble population has a diameter in the range 1 to 10.

SPECIFIC DESIGN

We have also develop the special products :

Probes (1) :

- different design

- multiple probes (3 or 4 sensors)

- double probe (1 optical probe +

1 thermocouple) for void

measurement, temperature

measurement, etc...

Mechanics (1) :

- mechanical mounting and removing

system (manuel or automatic)

(1) for more information, please contact us