Analysis on Nonlinearity of Ultrasonic Parameters in Biomaterial Engineering

Sonication with ultrasonic cavitation is one of effective and economical techniques for biomaterial processing in a lot of fields. Ultrasonic cavitation has become an important research subject. The latest research advances of ultrasonic cavitation and the reactions between cavitation and biomaterial are widely used in biomaterial engineering. Chinese traditional medicine extraction assisted with power ultrasound is one of the innovative techniques nowadays in point of fact. However, the nonlinearity and the spatio-temporal vicissitude of acoustic characters within the ultrasonic kettle are very complicated and variational. The nonlinearity of the acoustic characteristics makes the distribution of ultrasonic energy in the ultrasonic processor not symmetrical in spatial and time dimensions (x, y, z, t). So, the parameter nonlinearity causes some difficulties in the applied ultrasonic engineering. It must be well realized and dealt with seriously. Two respects of nonlinearity problems are introduced in the paper, which involve the nonlinearity analysis and nonlinear compensation methods. The topics are: (1) analysis on description methods of nonlinearity and research on some nonlinearity rules about the acoustic parameters of ultrasonic propagation in the mixture of biomaterials and mediums; (2) carry out experiments on nonlinearity of acoustic cavitation in fluid medium. The analysis methods are: (1) with mathematics, some rules of wave propagation and nonlinear relations of momentum in fluids are discussed; (2) in lossy and nonlinear media from arbitrary shaped sources, a free from paraxial approximation and efficient numerical algorithm capable of acoustic fields is described; (3) the nonlinearity of the spatial distribution of cavitation activity generated within ultrasonic processing vessel is studied. Based on the data of experiments, some applied biomaterial extraction vessels were set up for Chinese traditional herb medicine extraction. The results have been p- roved with experiments that the analyses on ultrasonic nonlinearity are practical and correct, and the methods of nonlinear compensation are proper, effective and useful for biomaterial extraction in practical engineering.