A TECHNIQUE FOR REAL-TIME MEASUREMENT OF FLOW TOPOLOGY IN TWO-PHASE SYSTEMS

A THREE-DIMENSIONAL QUANTITATIVE DIELECTRIC IMAGING TECHNIQUE IS PROPOSED FOR MEASUREMENT OF VOID FRACTION, INTERFACIAL AREA, AND FLOW TOPOLOGY OF LIQUID TWO-PHASE FLOWS. WITH MICROWAVES AS PROBING RADIATION, IT MEASURES THE SCATTERING FIELDS USING AN ARRAY AND, THROUGH AN INVERSE SCATTERING PROCESS, RECONSTRUCTS THE DIELECTRIC PERMITTIVITY, BOTH REAL AND IMAGINARY PARTS, OF EVERY PIXEL OF THE FLOW BODY. FLOW PARAMETERS, SUCH AS VOID FRACTION AND INTERFACIAL AREA, ARE THEN COMPUTED BY A STATISTICAL SOFTWARE. THE TECHNIQUE IS EXPECTED TO YIELD A RESOLUTION LIMITED ONLY BY SIGNAL-TO-NOISE RATIO, AND NOT BY THE WAVELENGTH OR DIFFRACTION. WAVELENGTH PLACES A LIMIT ON RESOLUTION ONLY IN THE CASE WHERE SOME FAR-FIELD APPROXIMATION IS USED FOR THE SCATTERING FIELD. TO OVERCOME THE WAVELENGTH LIMITATION AND TO RETRIEVE ALL THREE DIMENSIONS OF THE TARGET PROFILE, OUR APPROACH IS TO CONVERT THE SCATTERING EQUATION TO A SCATTERING MATRIX FORM WITHOUT NEGLECTING HIGHER ORDER TERMS. IN ORDER TO STABILIZE THE MATRIX INVERSION, SCATTERING DATA IN THE NEAR ZONE ARE EMPLOYED AND A LEAST-MEAN-SQUARE ALGORITHM IS DEVISED.