An Experimental and Numerical Investigation of Drag Reduction Through Biomimetic Modelling

This paper characterises flow around a circular cylinder and investigates the potential of a non-smooth surface to reduce air resistance in a Reynolds number range between Red = 8.09 104 and Red = 2.02 105. The two- and three-dimensional numerical simulations were performed using a steady-state solution and the Reynolds-averaged Navier-Stokes (RANS) approaches. Three different mesh designs and four turbulence models with various treatments were assessed and compared against experimental data. A total of 26 uneven preparations in the two-dimensional analysis and two riblet structures in the three-dimensional analysis were designed to investigate the effect of drag reduction. The results reported hold the potential of uneven structures to reduce the air resistance in the case of a circular cylinder. This research further demonstrates that engineering applications can benefit from mimicking nature's details and functions

A Numerical Bubbly Flow Investigation of Drag Reduction for Underwater Vehicles

This paper discusses the numerical investigation of dispersed bubbly flow within the boundary layer of a fully submerged axisymmetric body in horizontal position. The aim is to analyse the influence of injection position and bubble parameters on the drag reduction behaviour. The numerical study is conducted with the commercial CFD package ANSYS Fluent using the Eulerian-Eulerian modelling approach. Several sets of simulations are carried out with air injection velocities in the rage of 1 m/s to 15 m/s, injection locations between 0 and 0.5 m, and bubble diameters from 0.1 mm to 2 mm. In order to obtain the percentage drag reduction the results are correlated with a model without air injection. The simulations demonstrate a different behaviour between small and large bubble diameters of 0.1 mm and 2 mm respectively. Small bubbles archive drag reduction rates around 10% almost independent from the injection velocity and position, while large bubbles are highly affected by those parameters. The maximum drag reduction of 20.67% is achieved by injecting bubbles of 2 mm diameter with a velocity of 12.5 m/s at the tip of the prow nose. It is presented that the drag reduction increases with increasing injection velocity and bubble diameter. These parameters enable the bubbles to build up a continuous film across large parts of the hull which is required for a sufficient drag reduction

Numerical design and optimisation of a novel heatsink using ANSYS steady-state thermal analysis

This paper presents a numerical study of thermal performance on heatsink configurations for power electronic devices. The analysis was based on numerical modelling using the CFD software ANSYS 19.1 Steady-State Thermal. The heatsink geometrical features are investigated and compared with each other. The effects of material selection, total surface area, temperature uniformity and maximum surface temperature are assessed. The increase of surface area, implementation of geometrical features, and high thermal conductive material was found to reduce the maximum surface temperature and improve overall thermal dissipation capacity. With a constrained base (50mm × 50mm × 5mm), the novel designs incorporating secondary branches lead to best thermal performance, achieving up to 50% improvement in thermal efficiency. It was concluded that the implementation of nature inspired geometrical features and material configuration, studied in this work exhibits significant benefits for applications in heatsink for electronic devices

Numerical investigation and static structural analysis of deep groove ball bearings using ANSYS FEA

This paper provides a numerical investigation of material configurations for deep groove ball bearing. The static structural analysis was numerically modelled using ANSYS 18.2 FEA for deep groove 6210 ball bearing. Successful validation was achieved with theoretical and ANSYS values resulting in good agreement. The 6210 ball bearing is numerically investigated by implementing 4 different materials for respective components and a fixed radial load of 1 kN. The effects of total deformation, shear stress, equivalent Von-Mises stress, and equivalent stain are assessed theoretically and numerically. The adoption of different materials resulted in a hybrid ball bearing, achieving lowest total deformation of 5.6 µm, when compared with benchmark model. It was concluded that hybrid ball bearing incorporating different materials for key respective components studied in this work exhibited significant benefits for the application of deep groove ball bearings for electric drives

Conversion of Conventional Switching Mode Power Supply into a Photovoltaic Array Emulator

The paper discusses the development of a solar photovoltaic array emulator based on the conversion of a conventional switching mode power supply. The current-voltage characteristic of the power supply is adjusted according to the photovoltaic array model due to the injection of current into the junction of the feedback voltage divider circuit through an additional resistor. NI data acquisition device and Lab View software are used to build the emulator control system. The photovoltaic array model was implemented into the software algorithm as a look-up table to reduce the processing time and improve the system response. An “off-the-shelf” switching mode power supply having the flyback architecture and 230V ac input was selected for the practical experiment. The proposed approach to emulator development ensures rapid system prototyping at a low cost

Temperature gradient improvement of power semiconductor modules cooled using forced air heat sink

This paper discusses the improvement of operational reliability and lifetime of power electronic modules due to the reduction of the temperature gradient in the semiconductor structures. High temperature gradient in the power electronic modules having a large area of the semiconductor structure is a more affecting issue than the junction temperature. The improvement in the temperature gradient is achieved by varying/degrading the thermal resistance along the heat sink length. A conventional cooling system for three semiconductor modules based on a forced air heat sink was modelled and analysed to derive a reduction rate of the appropriate thermal resistances. Implementation of the forced air heat sink having non-uniformed thermal resistances along the heat sink length ensures the uniform temperature distribution across the power semiconductors and, therefore, the improved thermal gradient

Thin CdTe layers deposited by a chamberless inline process using MOCVD, simulation and experiment

The deposition of thin Cadmium Telluride (CdTe) layers was performed by a chamberless metalorganic chemical vapour deposition process, and trends in growth rates were compared with computational fluid dynamics numerical modelling. Dimethylcadmium and diisopropyltelluride were used as the reactants, released from a recently developed coating head orientated above the glass substrate (of area 15 × 15 cm2). Depositions were performed in static mode and dynamic mode (i.e., over a moving substrate). The deposited CdTe film weights were compared against the calculated theoretical value of the molar supply of the precursors, in order to estimate material utilisation. The numerical simulation gave insight into the effect that the exhaust’s restricted flow orifice configuration had on the deposition uniformity observed in the static experiments. It was shown that > 59% of material utilisation could be achieved under favourable deposition conditions. The activation energy determined from the Arrhenius plot of growth rate was ~ 60 kJ/mol and was in good agreement with previously reported CdTe growth using metalorganic chemical vapour deposition (MOCVD). Process requirements for using a chamberless environment for the inline deposition of compound semiconductor layers were presented

A test rig for thermal analysis of heat sinks for power electronic applications

This paper discusses the design and manufacture of a test rig for practical thermal analysis of the temperature distribution across forced air-cooled heat sinks. High-temperature gradients across power electronic modules that have a large area of semiconductor structure can result in premature failure of the components due to mechanical stress-related fatigue. Computer modelling and simulations predict the temperature distribution across the heat sink, but physical temperature measurements are required to validate these results. In order to acquire these temperature readings, a bespoke test rig is designed and manufactured. Temperature readings obtained using this test rig are applied for comparison to those obtained by computer simulation and, hence provide validation of the computer simulation results

Ubiquitous Control of a CNC Machine: Proof of Concept for Industrial IoT Applications

In this paper, an integrated system to control and manage a state-of-the-art industrial computer numerical control (CNC) machine (Studer S33) using a commercially available tablet (Samsung Galaxy Tablet S2) is presented as a proof of concept (PoC) for the ubiquitous control of industrial machines. As a PoC, the proposed system provides useful insights to support the further development of full-fledged systems for Industrial Internet of Things (IIoT) applications. The proposed system allows for the quasi-decentralisation of the control architecture of conventional programmable logic controller (PLC)-based industrial control systems (ICSs) through data and information exchange over the transmission control protocol and the internet protocol (TCP/IP) suite using multiple agents. Based on the TCP/IP suite, a network device (Samsung Galaxy Tablet S2) and a process field net (PROFINET) device (Siemens Simatic S7-1200) are interfaced using a single-board computer (Raspberry Pi 4). An override system mainly comprising emergency stop and acknowledge buttons is also configured using the single-board computer. The input signals from the override system are transmitted to the PROFINET device (i.e., the industrial control unit (ICU)) over TCP/IP. A fully functional working prototype is realised as a PoC for an integrated system designated for the wireless and ubiquitous control of the CNC machine. The working prototype as an entity mainly comprises a mobile (handheld) touch-sensitive human-machine interface (HMI), a shielded single-board computer, and an override system, all fitted into a compact case with physical dimensions of 300 mm by 180 mm by 175 mm. To avert potential cyber attacks or threats to a reasonable extent and to guarantee the security of the PoC, a multi-factor authentication (MFA) including an administrative password and an IP address is implemented to control the access to the web-based ubiquitous HMI proffered by the PoC

Review of low aspect ratio blade dynamics for electrical axial fans and compressors

The quest for lighter and shorter propulsion systems has led to the reduction of axial compressor and fan blade chord-lengths. Theoretical and experimental results show that the geometrical aspect-ratio criterion significantly affects the overall performance of axial flow compressors and fans. In conducting this review, it was found that the experimental results differ from one literature source to another. Highlighting that the way in which blade aspect ratio affects the performance of axial flow compressors and fans is still not fully understood. Nonetheless, the reviewed literature has still proven valuable for compressor and fan design. This paper focuses on creating a review of the available literature relating to how low aspect ratio blades may affect the performance of electrical axial compressors and fans