The microfluid jet polishing (MFJP) process is a manufacturing technology in which small abrasive particles (such as diamond, alumina, and ceria) are premixed with a carrier fluid (typically water) to form a liquid suspension that is pressurized and expelled through a nozzle for material removal. The resulting microjet beam—with a typical nozzle exit diameter in the range from 0.1 to 1.0 mm—impinges the workpiece surface for material removal by erosion and/or abrasion and produces an ultraprecision surface. This work applies a computational fluid dynamics (CFD) model to analyze the key phenomena in the interaction of the liquid suspension and the workpiece surface. The liquid film characteristics (film height, minimum film height, positions of the minimum film height, and hydraulic jump) obtained from the CFD simulations are compared with the results derived from empirical formulations found in the literature. Subsequently, the numerical results are utilized to investigate the impact velocity, pressure distribution, and shear stress caused by the suspension on the workpiece surface. It is observed that the shear stress strongly depends on the injection pressure of the liquid suspension and is weakly dependent on the abrasive suspension concentration (the liquid suspension with different densities, viscosities, and surface tensions). Additionally, the particle behavior is investigated in order to estimate the impact velocity and to identify the impact and erosion zones of the liquid suspension on the workpiece surface. Numerical results indicate that ~50% of total particles are impinging the workpiece surface almost perpendicularly (with a mean impact angle of ~86 degrees) for the first time in the stagnation region, where they are strongly decelerated by the carrier fluid before they reach the workpiece surface. These particles, however, rebound on the surface and are reaccelerated by the carrier fluid, impinging the workpiece surface further in the radial direction.

Production of functional nanoparticles and nanoscaled powders is a key process in several recent industrial applications. In this work, the flame process in nanoparticle production in sprays is analyzed. Specific focus is on the flow behavior, the temperature distribution, and the residence-time of particles in the hot (reactive) regions in a flame spray reactor that are analyzed by numerical simulations using computational fluid dynamics techniques. The role of the co-flowing gas rate provided to the flame spray reactor and its effects on the spray behavior, flame morphology, and particle properties in an enclosed atmosphere is highlighted. The influence of different operational conditions on the reactor temperature and temperature-residence-time distribution of gas and particles is investigated. It is found that providing a reduced co-flowing gas rate to the flame spray reactor favors the recirculation of hot gas, and, consequently increases the residence-time of particles in the high-temperature regions. The numerical results of particle diameter and gas-phase temperature are compared to some existing experimental data.

Metalworking operations rely on the successful application of metalworking fluids (MWFs) for effective and efficient operation. Processes such as grinding or drilling often require the use of MWFs for cooling, lubrication, and chip removal. Electrochemical machining processes require electrolyte flow to operate. However, in those machining operations, a fundamental understanding of the mode of action of MWF is lacking due to the unknown flow dynamics and its interaction with the material removal during the process. Important information on the behaviour of MWFs during machining can be obtained from specific experimental flow visualisation studies. In this paper, promising flow visualisation analysis techniques applied to exemplary machining processes (grinding, sawing, drilling, and electrochemical machining) are presented and discussed. Shadowgraph imaging and flow measurements, e.g., particle image velocimetry, allow the identification of typical flow and MWF operating regimes in the different machining processes. Based on the identification of these regimes, efficient machining parameters and MWF applications can be derived. In addition, detailed experimental analyses of MWFs provide essential data for the input and validation of model development and numerical simulations within the Priority Programme SPP 2231 FluSimPro.