Passive acoustics process to monitor fluidized bed flow

A method for the non-intrusive determination of flow anisotropy through a two phase fluid bed in a structure comprising:

• (a) measuring wall vibrations of said structure and then determining the power spectrum as a function of frequency, said wall vibrations taken at several first positions circumferentially about the structure,
• (b) determining the area of the power spectrum which includes a resonance peak for each of said first positions,
• (c) correlating a change in said area between adjacent first positions of the power spectrum with flow anisotropy through the cross-section of said structure bounded by the circumference including said several first positions.