Advances in ultrasonic monitoring of oil-in-water emulsions

• Multiple scattering of thermal waves is analyzed.
• A new model formulation is presented for effective wavenumber of emulsions.
• Calculations show attenuation reduced due to thermal multi-mode scattering
• Results are compared with experimental data for an emulsion.

A modification to the multiple scattering model used to interpret ultrasonic measurements for emulsions is investigated. The new model is based on a development by Luppé, Conoir, and Norris (2012) which accounts for the effects of multiple mode conversions between thermal, shear and compressional modes. The model is here applied to the case of oil in water emulsions in which thermal effects are dominant. The additional contributions are expressed in terms of the scattering coefficients for conversion between compressional and thermal modes and vice versa. These terms are due to the effect of thermal waves produced at one particle being reconverted into the compressional mode at neighboring particles. The effects are demonstrated by numerical simulations for a sunflower oil in water emulsion which show that the additional terms are significant at low frequency and high concentrations. Comparison is also made with experimental data for a hexadecane in water emulsion. Although qualitative agreement is demonstrated, there are some quantitative differences, which are attributed to uncertainties in the physical properties, in the experimental data, or in the assumptions made in the model.

Figure optionsDownload as PowerPoint slide