The aim of this study was to evaluate the device performance of a new design by comparing with a typical commercial DPI. Computational fluid dynamics (CFD) coupled with the discrete element method (DEM) collision has been utilized in this study to characterize and examine the flow field and particle transportation, respectively. A typical commercial DPI and an in-house designed novel DPI with distinct design features were compared to explore their dispersion capabilities and suitability for delivery to the respiratory tract. For this exploration, realistic oral to larynx and tracheobronchial airway models consisting of bio-relevant features were adopted to enhance practical feasibility. Distinct aerosol performances were observed between the two DPIs in the respiratory tract, where the in-house DPI, in comparison with the commercial DPI, has shown approximately 30% lower deposition fraction in the mouth-throat region with approximately 7% higher escape rate in the tracheobronchial region under the identical inhalation condition. This observation demonstrates that a novel in-house designed DPI provides higher device efficiency over the selected typical commercial DPI.

Wire arc additive manufacturing (WAAM) is a metal additive manufacturing (AM) process attracting interest from the automotive, defence, aerospace, architecture/engineering/construction and other industries because of its ability to manufacture large metal parts cost-effectively. Nevertheless, problems such as part defects and process efficiency remain, and consequently, efforts to improve WAAM are continuing. The WAAM process involves physical phenomena that include fluid flow, heat transfer, phase changes including melting, solidification and vaporization, multi-phase interactions, and deformations resulting from residual stresses—so obtaining a complete understanding is challenging. While numerical modelling is widely used to understand and assist with developing processes, modelling of AM processes such as WAAM is sophisticated because of their multi-physics and multiscale nature. This review addresses the existing and likely future roles of numerical modelling in advancing WAAM technology. Consideration is given to the known problems with WAAM, the different types of numerical modelling, including computational fluid dynamics, the finite element method, and smoothed particle hydrodynamics, and their potential to address persistent issues. Additionally, this review seeks to provide an understanding of the physics associated with the WAAM process, examines the trends in the development of WAAM technology, and recommends possible future directions. These include the combination of different physics-based modelling approaches to overcome their individual shortcomings, and the inclusion of modelling as part of a digital twin of the WAAM process.

The autogenous manual gas tungsten arc welding (GTAW) process was used for cladding austenitic stainless steel 316L using a single pass with various contact tip-to-work distances (CTWDs). Immersion and electrochemical tests were used to evaluate the corrosion resistance of the welded specimens, and a microstructural analysis was conducted to investigate the chemical composition of the molten pool and the heat-affected zone of welding. The key findings of this study indicate that the corrosion resistance improved under a CTWD of 5 mm due to the optimal distribution of ferrite and a refined microstructure. Additionally, the highest hardness was observed in specimens with a CTWD of 3 mm, attributed to the increased ferrite content in the weld metal. As the CTWD increased, the ferrite fraction decreased, and the hardness also diminished. However, in the CTWD 7 mm case, the higher heat input influenced the microstructure and molten pool shape significantly through the Marangoni effect, resulting in a lower corrosion resistance. These results suggest that optimizing the CTWD can enhance the corrosion resistance of welded 316L stainless steel.