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Stream finishing is accepted as one of the post processing operations. It is not only capable of grinding but also offers polishing of additive manufactured components, having advantages of larger material removal rates and controllable toolpath. We have developed a stream finishing model through semi quantitative prediction via computational fluid dynamics (CFD) simulations. The scheme couples the granular flow field with the material removal scheme by solving the granular flow using a continuum-based method. For the rheology, the media viscosity is determined to resolve the flow field so the pressure induced by the media and the material removal rate can be predicted. The model calibration involves developing a tribometer and using it to measure the media pressure for several scenarios based on the rotational speed of the drum (30 rpm), radial distances of the tribometer (100, 250, 400 mm), submerged depths (100, 200, 250 mm) and its glancing angles (0, 15°, 30°, 45°, 60°, 75°, 90°). The work is extended to study the media flow for a simplified square work piece. The results indicate that the particle velocities on the surface of the work piece predicted by simulations are comparable to those of experiments. They show similar patterns and magnitudes for the parameters tested, which demonstrate the capability of the model to correctly predict the granular flow field.

Ultrasonic cavitation bubble phenomena play a key role in numerous medical procedures such as ultrasound-assisted lipoplasty, phacoemulsification, lithotripsy, brain tumor surgery, muscle and bone therapies and intraocular or transdermal drug delivery. This study investigates numerically the interaction of a bubble with a bio-material (fat, skin, cornea, brain, muscle, cartilage or bone) involved in the treatments mentioned when subjected to an ultrasound field. A range of frequencies is used to study the bubble behavior in terms of its growth and collapse shapes, and the maximum jet velocity attained. Simulation results show complex dynamic behaviors of the bubble. In several cases a jet is formed directed away from the bio-material while in others, toward it. In certain cases, the bubble eventually breaks into two, with or without the formation of opposite penetrating jets. Very high maximum velocities of jets directing away or toward the bio-materials can be observed in some cases (700 to 900 ms−1). (E-mail: mpekbc@nus.edu.sg)

The effect of nozzle shape, angle and length on the propulsive performance of continuously rotating detonation engine is numerically investigated in a three-dimensional annular chamber with the one-step chemical kinetics of a hydrogen and air mixture. The thrust and specific impulse of the rotating detonation engine with four different nozzles are evaluated to find out the best performance nozzle shape. This chosen nozzle shape is used as a baseline nozzle. In addition to the description of a detailed flowfield structure in the chamber with the baseline nozzle, the changes in flowfield properties at the chamber inlet and nozzle exit due to nozzle shapes are also investigated. With the baseline nozzle, the evaluation on the effect of nozzle angle and length is performed. The best engine performance and less total pressure loss are achieved in the divergent nozzle with the nozzle angle of 10 ◦ and the nozzle length of 0.04 m. However, the rotating detonation engine has the negligible nozzle effect on the propulsive performance, compared with that for pulse detonation engine.

High intensity soundwaves, such as shockwaves and HIFU, are widely used in biomedical applications, for example, extracorporeal shockwaves lithotripsy (ESWL) and HIFU prostate cancer treatment. The high pressure in the tissue and nearby fluid often causes formation of cavitation bubbles. Our previous simulation results via BEM approach show complex bubble ultrasound interactions: in certain cases a jet is formed directed away from the nearby tissue while in others, towards it [Fong et al., Ultrasound Biol. Med., 32(6), 925–942, 2006]. In the present work, pulsed ultrasound microbubble interaction is studied using the same code to provide further understanding to the jetting behavior of the bubbles near (different) biomaterial surface which is critical to the success of tissue ablation and the minimization of auxiliary damages. Separately, we have also simulated shockwave bubble interaction using the BEM code with excellent concurrence to other compressible numerical schemes such as arbitrary Lagrangian‐Eulerian and free Lagrange methods [Klaseboer et al., Comput. Methods Appl. Mech. Eng. 195, 4287–4302 (2006)] and experiments. It is suggested that the (primary) dynamic response of the bubble to soundwaves is mainly inertia controlled since compressibility of the fluid is not modeled.