Fluid-velocity measurements and flow-pattern identification by noise-analysis of light-beam signals

For fluid-velocity measurements of the two-phase flow in reactor safety experiments, a new method has been developed. This method is based on cross-correlating the signals of two light-beam detectors, which cross the diameter of the test-section (no flow restriction).

Furthermore, the signals of the two detectors are also used to give a rough estimate of the flow-pattern of the investigated two-phase flow. This flow-pattern identification is performed by comparing several characteristic functions (like the spectra and probability-functions of the signals) of a known flow-pattern recorded in an air-water test-facility, with equivalent functions of the investigated two-phase flow. This flow-pattern identification is performed by comparing several characteristic functions (like the spectra and probability-functions of the signals) of a known flow-pattern recorded in an air-water test-facility, with equivalent functions of the investigated two-phase flow. An important requirement for these comparisons is the appropriate normalization of the abscissa of the characteristic-functions, which is performed with the time-averaged fluid velocity.

As an example, the results of a blow-down experiment are shown. Velocities up to 300 m/s could be measured within a pressure range up to 50 bars and temperatures up to 280°C. Flow-regime changes were observed in three different parts of the blow-down.