Theoretical investigation of the levitation force generated by underwater squeeze action

Previous research has experimentally demonstrated the feasibility of near-field acoustic levitation (NFAL) in water. This paper proposes an analytical model of underwater NFAL to study its levitation performance. At first, the fluid's compressibility must be determined because it is significant to the model's accuracy. Therefore, the Reynolds equations describing the film pressure distribution are deduced based on fluid film lubrication theory for incompressible and compressible fluids. The calculated squeeze film forces for each case are compared with experimental observations from the literature to confirm the fluid's compressibility. The comparison results show that the theoretical numerical results under the compressible condition are closer than the incompressible condition to the experimental data. Further numerical results show that increasing the water temperature decreases the mean squeeze film force when the water temperature is higher than 20 degrees C. In addition, the mean squeeze film force is increased by increasing the vibration amplitude.

Automated summary

This study proposes an analytical model for underwater near-field acoustic levitation (NFAL) and investigates its levitation performance. The study deduces the Reynolds equations to describe the film pressure distribution and determine the compressibility of the fluid. The comparison of calculated squeeze film forces with experimental observations confirms the fluid's compressibility. The numerical results show that increasing the water temperature decreases the mean squeeze film force above 20 degrees C, while increasing the vibration amplitude increases the mean squeeze film force.