Efficient internal mixing stands as a pivotal requirement for droplet-based micro-reactors/micro-mixers facilitated by microfluidic systems. Among the various methods for their production, capillary-generated droplets emerge as a notable approach. Understanding the role of coaxiality within coflow microfluidic devices in influencing internal mixing remains a crucial aspect for optimizing these systems. Coaxiality within inserted cylindrical capillaries significantly affects mixing efficiency according to our experimental observations. Through numerical simulations, the intricate mixing dynamics of reagents inside droplet generated via a coflow capillary microfluidic system has been investigated. We demonstrate that coaxiality profoundly impacts the initial distribution of disperse phases within droplets, shaping subsequent internal mixing dynamics. Contrary to previous assumptions, our findings highlight the substantial impact of marginal deviations in coaxiality, around 20%, on optimizing mixing efficiency. This challenges prior beliefs and emphasizes the nuanced role of coaxiality in microfluidic systems. These insights advance our understanding of coaxiality's critical influence on enhancing mixing efficiency within coflow microfluidic devices, paving the way for improved design strategies and applications in diverse scientific fields.

The resistance of a large Pure Car Truck Carrier (PCTC) with a bulbous bow and a transom stern is evaluated in the present paper. Several cases at nine different ship speeds in calm water are simulated and results are compared with the experimental measurements. The maximum relative error is 0.93% at a Froude number (Fr) of 0.209. The total resistance coefficient of the ship in calm water shows a parabolic trend with increasing Fr, and it reaches a minimum value at Fr = 0.1794. Furthermore, the cases of the ship in regular waves with six different wavelengths and three wave heights are simulated. It is observed that the total resistance exhibits a quadratic relationship with the wavelength when the wave height is fixed. The wave-making resistance increases with the increase in wave height at any fixed wavelength, and it reaches a maximum value when the wave-length is 1.2 times the ship length (L_pp). Additionally, we also investigated the resistance in three different sea states at four different speeds. When the significant wave height of irregular waves is the same as regular waves, the wave-making resistance under irregular waves is much smaller than that of the regular waves. All of these results indicate that the bulbous bow and transom stern can reduce the wave-making and residuary resistances, which can provide a useful reference for the subsequent design and manufacturing of related ships.

Ship propulsion performance is important for navigating. This study aims to enhance the propulsion performance of a 9500 DWT ship by integrating PBCFs into the hull–rudder–propeller–coupled system. A total of 27 PBCF models with different fin installation angles, radius ratio, and tilt angles are designed in the study. The computational fluid dynamics method is employed and a propeller open-water test is also performed to optimize the PBCF design, which is integrated into different coupled systems. The numerical results show that the PBCFs exhibit differential enhancements of propeller performance across system configurations with their efficiency changing from 4.05% to 2.87%. Moreover, the reliability of ship self-propulsion simulation is mutually validated through the combined BF (body force) and MRF (multi-reference frame) methods. Then, simulations were conducted using these two methods for the self-propulsion of a 9500 DWT ship at three different speeds. Finally, the results from using the MRF method show that the incorporation of PBCFs can reduce delivered power to propeller by 1.32% at different F_r.