Reconstructing three-dimensional fluid velocity vector and temperature fields from acoustic transmission measurements.

A theory with supporting experimental evidence, is presented for reconstructing the three-dimensional fluid velocity vector field and temperature field, in a moving medium from a set of measurements of the acoustic propagation time, between a multiplicity of transmitter and receiver locations on a stationary boundary surface. The inversion of the integrals relating the acoustic propagation path, to the propagation time measurements is affected by linearization and discrete approximation of the integrals and application of an algebraic reconstruction technique (ART). The inversion of these integrals provides reconstructions of both acoustic refractive index and vector fluid velocity. Temperature reconstructions are obtained from the temperature dependence of acoustic refractive index. The problem of the presence of certain invisible fluid functions is treated. Since this technique does not require the presence of scattering centres or the optical transparency of the medium, it may be applied in many cases (i.e. , turbid, opaque, or chemically pure media) where Doppler or optical (e.g. , laser holography) methods fail. (A)