Numerical investigation of ultrasound focusing and bubble collapse

Evaluation of the effect of ultrasound-assisted hot air drying on the drying characteristics and physicochemical properties of cherries based on the entropy-weighted TOPSIS method

To address the challenges associated with prolonged traditional hot air drying (HAD) times and significant nutrient loss in cherries, this study employs ultrasound-assisted hot air drying (USA-HAD) technology. The study investigates the impacts of various ultrasound (US) frequencies, US powers, and hot air temperatures on the drying kinetics, physicochemical properties, texture attributes, and microstructure of cherries during drying. Cherry physicochemical quality serves as the evaluation criterion, with the entropy-weighted TOPSIS method used to identify the optimal drying parameters. The findings indicate that USA-HAD accelerates the drying process, reduces drying time, and enhances drying efficiency. In comparison to natural drying, USA-HAD significantly preserves polysaccharides, total phenolic content, total flavonoid content, and organic acids in cherries, while boosting antioxidant activity. Concurrently, it reduces color intensity, as well as the hardness, chewiness, and gumminess of dried cherry products. Microstructural observations under different drying methods reveal an increase in surface micropores and relatively intact tissue structure. Under conditions of 55°C, 48 W, and 28 kHz, cherries exhibit superior overall quality based on the TOPSIS relative closeness degree. This study offers practical insights for optimizing post-harvest processing of cherries. PRACTICAL APPLICATION: In this rapidly evolving era, the application of combination drying technology is clearly on the rise. The USA-HAD treated cherries had better nutritional and bioactive than HAD. The conclusions obtained indicate that the USA-HAD technology has more potential for development.

Numerical investigation of acoustic cavitation and viscoelastic tissue deformation

Acoustic cavitation and tissue deformation are studied by modifying a level-set method for compressible two-phase flows to consider viscoelastic tissue deformation. The numerical simulations performed using different shear moduli and bubble-tissue distances demonstrate various interactions between bubble and viscoelastic tissue, including inverted cone-shape bubbles, bubble migration, liquid jet formation, compressive and expansive tissue deformation, and tissue perforation. The bubble is observed to grow larger with increasing tissue bulk modulus and density. The maximum tissue deformation generally increases with decreasing initial bubble-tissue distance and with increasing tissue bulk modulus and density. The tissue shear modulus conditions that maximize tissue deformation are in the range of 1-10 MPa, unless the tissue density is very large.