The purpose of this study is to investigate the effects of acoustic streaming and acoustic radiation force on particles motion in an ultrasonic standing wave. A flexural vibration plate with 4 nodes was designed, and it was shown that the amplitude at the antinode is proportional to the voltage. This means it is possible to conduct experiments with any amplitude. After confirming that a standing wave field was generated in closed space, an experiment was carried out to visualize acoustic streaming. Eight vortices were observed in the horizontal direction, indicating a Rayleigh acoustic flow. In addition, a vortex in perpendicular direction against the plate was generated when the height between vibration plate and acrylic surface was set at half wavelength. Then two vortexes were obtained at a wave length for the height. Simulations for acoustic pressure and streaming agreed with this experimental result. Finally, simulations on particle motion showed that acoustic flow dominates when particle diameter is less than 20 μm. On the other hand, the motion of over 20 μm particle is influenced by acoustic radiation force.

This study explores the applicability of computational fluid dynamics (CFD) simulation using the Moving Particle Simulation (MPS) method to the deformation behavior of food pastes during extrusion-based 3D food printing (3DFP). Rice flour pastes with varying viscosities were prepared and printed into cylindrical shapes using a custom-built 3DFP device. Corresponding simulations were conducted with commercial MPS software Particleworks, incorporating experimental rheological measurements. Three viscosity models, Power-law, Bingham, and Herschel-Bulkley were compared. While the Power-law model underestimated shape retention for high-viscosity samples, and the Bingham model overestimated viscosity for low-viscosity pastes, the Herschel-Bulkley model closely reproduced experimental results across all conditions. These findings demonstrate that the MPS method, combined with an appropriate viscosity model, can accurately simulate shape deformation in 3DFP processes. The approach provides a promising tool for optimizing material properties and printing conditions in food manufacturing, potentially reducing the need for trial-and-error experimentation.

The bulk ceramics with high functionality and reliability are not possible without microstructure morphology control. Since sintering is the phenomenon of forming physical bonds at the contact points of particles, the particle-assembled structure before densification is the basis of microstructure morphology and a process factor that must be controlled. The application of a high isotropic pressure of 1000 MPa not only improves the homogeneity and filling of the particle-assembled structure, but also increases the chemical potential, and promotes the dissolution of solid particles into the solvent without heating. This paper outlines a technology for densifying bulk ceramics at room temperature based on the control of the particle-assembled structure (Reaction Sintering with Cold Isostatic Press: RS-CIP). As an example of the application of this technique, fluorescent materials composed of nitride phosphor particles and a MgO matrix are also introduced.