This study explores the efficacy of dimples in influencing the aerodynamic performance of a straight rectangular wing. Computational Fluid Dynamics based numerical simulations were performed to model turbulent flow and quantify the forces exerted on the wing. The k-ω Shear-Stress Transport turbulence model was chosen to solve the underlying equations. To ascertain reliability, the results of numerical simulations were compared with both experimental and simulation results of the previous studies. The impact of various dimple configurations, placed at 15%, 50% and 85% of the chord length, on the aerodynamic performance of the wing was investigated. The evaluation involved analyzing the drag coefficient (C_D), lift coefficient (C_L), lift-to-drag (L/D) ratio, streamlines and the flow field around wing in both chordwise and spanwise directions. The findings indicated that a wing with a dimpled surface could yield a reduced drag coefficient of up to 6.6% compared to the unmodified wing. This reduction is attributed to the dimples ability to sustain attached airflow and delay flow separation. The results demonstrated negligible deviation in the lift coefficient with the incorporation of dimples. The incorporation of dimples on the wing surface has been demonstrated to enhance the aerodynamic performance of lifting surfaces.

The integrated motor pump-jet (IMP) propulsion system is a form of modern underwater vehicle propulsion that uses a modular design paradigm. The integrated motor propulsor is a compact construction consisting of a permanent magnet (PM) and a pump-jet propulsor, as well as the propulsion and electrical systems. Compactness, great reliability, and low noise are the most significant features of this technology. The primary technology research status and main application configurations of propulsion devices with an integrated motor were examined based on the working principles and attributes of the devices. The theoretical and experimental research on the design, performance analysis, and control of IMPs is discussed, covering electric motors; bearing structures; hydrodynamic design; and hydrodynamic, electromagnetic, and bearing coupling design technology. This research investigates the most recent research goals, progress, and applications of IMPs, which includes their hydrodynamic performance, cavitation, and gap flow. Finally, the future essential technologies of high power, low vibration, water-lubricated bearings, electromagnetic and bearing coupling design, and IMP antipollution and antidamage capacity are summarized.

This paper aims to identify and study the blood flow and acoustics characteristics of different degrees of stenosis in the carotid artery. Blood flow will produce acoustics, but the presence of different levels of stenosis are expected to produce different acoustic characteristics. The blood flow and acoustic characteristics are simulated by using computational fluid dynamics software (CFD). Several three-dimensional models of carotid arteries that have different degrees of stenosis are used together with a normal/healthy carotid artery - i.e., 30% and 70% degrees of blockage. The geometry of 30% and 70% stenosed model are computationally generated from a normal carotid artery geometry. In addition, the blood viscosity level was also increased in this study to a value of 0.005 kgms-1 (from the normal viscosity of 0.004 kgms-1) to compare the effect of hyperglycaemia (i.e., diabetes mellitus) that may bring additional complications to blood flow. Pulsatile simulations are used for all cases in order to mimic the exact blood flow condition in which the inlet velocity and outlet pressure change with time. The present study shows that as the degree of stenosis increases at the common carotid artery (CCA), the velocity at the internal carotid artery (ICA) and external carotid artery (ECA) outlet increases. The maximum velocity changes for ICA at the systolic peak from normal to 70% degree of stenosis for carotid artery shows an increase by 8%, while an opposite trend is observed for the maximum velocity changes of ECA at the systolic peak, where a reduction by 3% occurs from normal to 70% degree of stenosis for carotid artery. In terms of viscosity, as the viscosity of the blood increases, the velocity of the blood flow decreases in all geometry carotid arteries and may potentially provide further complications on clinical problems. The acoustic simulation showed that the acoustic power increases by 5% and 20% for carotid artery geometry that has 30% and 70% degree of stenosis, respectively. The present study indicates potential for further developing non-invasive acoustic means to diagnose and measure stenosis in carotid arteries.

Considerable research has been conducted in the past decade and a half regarding the bio-lubricants potential to replace mineral-based lubricants as mainstream lubricants such as engine oil, hydraulic oil, compressor oil, and metalworking oil. This study studied several bio-lubricants (rapeseed oil, palm olein, and soybean oil) and a mineral-based lubricant, SAE40. The bio-lubricants have better physiochemical, tribological characteristics and environmental friendly nature, and are promising to replace mineral-based lubricants. In this study, a journal bearing test rig (JBTR) was developed in order to investigate the effect of journal speed on the temperature of oil film with time. Additionally, the load-carrying capacity of bio-oils was tested against the mineral-based lubricant SAE40 by adding a load on the journal. For all three speeds, i.e., 1000, 1500, and 2000 rpm, the bio-lubricants recorded minimum temperature. At 1000 rpm, rapeseed oil recorded a 9.2% lower temperature than SAE40. Similarly, at 2000 rpm, rapeseed oil recorded a minimum temperature that was 2.5% lower than SAE40; in comparison, at 1500 rpm, palm olein recorded a minimum temperature that was 1.8% less than SAE40. Overall, the results of this study revealed that bio-oils recorded a lower temperature rise than mineral oil. These results are very encouraging for further research in this area.

AISI 4340 is a medium-carbon low-alloy steel that has gained distinctive attention due to its advanced properties including high strength, high toughness, and heat resistance. This has led to its commercial usage in a wide variety of industries such as construction, automotive, and aerospace. AISI 4340 is usually machined in a hardened state through a hard-turning process, which results in high heat generation, accelerated tool wear, low productivity, and poor surface quality. The application of high-speed machining helps improve the material removal rate and surface finish quality, yet the elevated temperature at the cutting zone still poses problems to the tool’s lifespan. Apart from using advanced cutting tool materials, which is costly, researchers have also explored various cooling methods to tackle the heat problem. This paper presents a review of a sustainable cooling method known as minimum quantity lubrication (MQL) for its application in the high-speed turning of AISI 4340 steel. This study is centered on high-speed turning and the application of MQL systems in machining AISI 4340 steel. It has been observed that the hard part turning of materials with a hardness exceeding 45 HRC offers advantages such as improved accuracy and tighter tolerances compared to traditional grinding methods. However, this process leads to increased temperatures, and MQL proves to be a viable alternative to dry conditions. Challenges in optimizing MQL performance include fluid penetration and lubrication effectiveness.

Aerodynamics of vehicles account for nearly 80% of fuel losses on the road. Today, the use of the Intelligent Transport System (ITS) allows vehicles to be guided at a distance close to each other and has been shown to help reduce the drag coefficients of the vehicles involved. In this article, the aim is to investigate the effect of distances between a three car platoons, to their drag and lift coefficients, using computational fluid dynamics. To that end, a computational fluid dynamics (CFD) simulation was first performed on a single case and platoon of two Ahmed car models using the STAR-CCM+ software, for validation with previous experimental studies. Significant drop in drag coefficients were observed on platoon models compared to a single model. Comparison between the k-w and k-e turbulence models for a two car platoon found that the k-w model more closely approximate the experimental results with errors of only 8.66% compared to 21.14% by k-e turbulence model. Further studies were undertaken to study the effects of various car gaps (0.5L, 1.0L and 1.5L; L = length of the car) to the aerodynamics of a three-car platoon using CFD simulation. Simulation results show that the lowest drag coefficient that impacts on vehicle fuel savings varies depending on the car's position. For the front car, the lowest drag coefficient (CD) can be seen for car gaps corresponding to X1 = 0.5L and X2 = 0.5L, where CD = 0.1217, while its lift coefficient (CL) was 0.0366 (X1 and X2 denoting first to second and second to third car distance respectively). For the middle car, the lowest drag coefficient occurred when X1 = 1.5L and X2 = 0.5L, which is 0.1397. The lift coefficient for this car was -0.0611. Meanwhile, for the last car, the lowest drag coefficient was observed when X1 = 0.5L and X2 = 1.5L, i.e. CD = 0.263. The lift coefficient for this car was 0.0452. In this study, the lowest drag coefficient yields the lowest lift coefficient. The study also found that for even X1 and X2 spacings, the drag coefficient increased steadily from the front to the last car, while the use of different spacings were found to decrease drag coefficient of the rear car compared to the front car and had a positive impact on platoon driving and fuel-saving.