Control of liquid flow profile from mode structure of ultrasonic signal

A possibility of recovering parameters of the viscous liquid flow according to the spectrum of the ultrasonic signal is considered. It's shown that the flow speed profile and, consequentially, the liquid viscosity can be restored on the base of the mode structure of the ultrasound field in the waveguide. For the solution of the inverse problem we use WKB-approximation. We used Abel's inversion of the dispersion equation for the constants of the modes propagation, analogues to the Bore-Zommerfeld rules in quantum mechanics. Such equation can be applied at large number of modes. In practice it's enough two or more modes to reconstruct waveguide profile. For flow speed profile reconstruction it's enough to know difference (discrete or continuous) between the modes constants of propagation. For such data obtaining it is experimentally possible to register interference (oscillations) of the ultrasonic signals of different frequencies in the fixed point of a waveguide. The error of the profile reconstruction does not exceed units of percents, that is quite acceptable in practice of diagnostics and flow detecting. The technique has been tested for optical waveguides and applied radiophysics. The results obtained can bee used for flowmeter development, which give the information about flow speed profile and the viscous properties of liquid.