On Nonlinear Scattering of Sound by Small Bubble in Polymeric Liquid
S.P.Levitsky (Negev Academic College of Engineering, Beer-Sheva, Israel )
The presence of free gas in polymers even in small amounts may lead to drastic changes both in technological processes and properties of final products. This is the reason why timely diagnostics of free gas content can play essential role in polymer technology. One of high perspective for a practical employment is the acoustic method based on nonlinear scattering of acoustic signal by dispersed bubbles. In the paper the generalized Rayleigh equation with viscoelastic contribution resulting from continuous spectrum of the liquid.s relaxation times is formulated and solved for small but finite bubble oscillations at acoustic excitation. The terms up to quadratic ones are accounted for (the volume approach, developed originally by E.Zabolotskaya, is used). The expression for pressure in the scattered wave, and the amplitude of second harmonics are defined and studied numerically. The results of simulations have showed that hereditary properties of the liquid highly influence the scattered signal and must be accounted for at acoustic measurements of bubble population in polymeric liquids.
Section : 4