Vibration Performance of a Flow Energy Converter behind Two Side-By-Side Cylinders

Flow-induced vibrations of a flexible cantilever plate, placed in various positions behind two side-by-side cylinders, were computationally investigated to determine optimal location for wake-excited energy harvesters. In the present study, the cylinders of equal diameter D were fixed at center-to-center gap ratio of T/D = 1.7 and immersed in sub-critical flow of Reynold number ReD = 10, 000. A three-dimensional Navier-Stokes flow solver in an Arbitrary Lagrangian-Eulerian (ALE) description was closely coupled to a non-linear finite element structural solver that was used to model the dynamics of a composite piezoelectric plate. The cantilever plate was fixed at several positions between 0.5 < x/D < 1.5 and -0.85 < y/D < 0.85 measured from the center gap between cylinders, and their flow-induced oscillations were compiled and analyzed. The results indicate that flexible plates located at the centerline between the cylinder pairs experience the lowest mean amplitude of oscillation. Maximum overall amplitude in oscillation is predicted when flexible plates are located in the intermediate off-center region downstream of both cylinders. Present findings indicate potential to further maximize wake-induced energy harvesting plates by exploiting their favorable positioning in the wake region behind two side-by-side cylinders. © 2019 by the authors

Micropower system optimization for the telecommunication towers based on various renewable energy sources

This study investigates the technical and cost-effective performance of options renewable energy sources to develop a green off-grid telecommunication tower to replace diesel generators in Malaysia. For this purpose, the solar, wind, pico-hydro energy, along with diesel generators, were examined to compare. In addition, the modeling of hybrid powering systems was conducted using hybrid optimization model for energy (HOMER) simulation based on techno-economic analysis to determine the optimal economically feasible system. The optimization findings showed that the hybrid high-efficiency fixed photovoltaic (PV) system with battery followed by 2 kW pico-hydropower and battery are the optimal configurations for powering off-grid telecommunication towers in Malaysia with the lowest net present cost (NPC) and cost of energy (COE). These costs of NPC and COE are more down than diesel generator costs with battery by 17.45%, 16.45%, 15.9%, and 15.5%, respectively. Furthermore, the economic evaluation of the high-efficiency solar fixed PV panels system annual cash flow compared to the diesel generator with the battery system indicated a ten-year payback period

Melting performance enhancement of thermal storage system by utilizing shape and position of double fin

In present study, a 2D rectangular enclosure was considered as a latent thermal energy storage (LTES) system. Lauric acid was used as PCM material. The aim of this study was to use fins to enhance melting process of PCM. Position and shape of double fins were considered as investigating parameters. At first stage three different positions were considered for fins of rectangular shape. Results indicated that amongst aforementioned cases, best results were achieved when double fins were located at lower half of enclosure. Results revealed that up to 1800s could be saved during whole melting process. At second step, two trapezoidal form and one triangular shaped double fins were used to evaluate the effect of fin shape. In these cases, fins were placed at optimum position concluded from previous stage. Results presented that up to Fo = 0.15, best values of Nusselt numbers were related to triangular shaped fins. After Fo = 0.15, the case with triangular fin has least Nu number. The best melting performance was related to triangular fins at which 1000s less melting time was observed. Enhancement ratio results presented better performance for triangular fins after second of 2500

Simulation of various cross-section shapes of spring-wire as a turbulator for spiral-pipe

Spring-wire has been recently suggested as a turbulator for curved based helical and spiral tubes because of its flexibility nature. Spring-wire can be fabricated by twisting a wire around a rod. However, common circular wire is the only one normally employed in the fabrication process of the spring-wire while the outcomes of this research show that the other wire cross-section shapes can provide much higher thermal performance and Nu number. Novel wire cross-sections for such as triangular, hexagonal, square, and rectangular are numerically simulated in this research (see graphical abstract). All recommended shapes are evaluated from frictional, exergetic and thermal viewpoints for a selected range of Dean number. Nu number of triangular cross section is almost double compared to the common circular cross section. Pressure drop also increases which can be considered as an important criterion depending on the application of the heat exchanger. Interesting thermal-fluid behavior are found through the spiral pipe under the mentioned spring-wire turbulator all of which are reported in this paper

The compression effect on aerodynamic properties of sports fabrics

Generally, the surface textures of the sport fabrics influence the aerodynamic properties of the athletes in motion. On the other hand, the surface texture of sports garments largely depends on the applied stress while wearing. Therefore, the fitting of garments on athlete bodies can make the aerodynamic behaviour more complex. Additionally, the fabric at an appropriate level of stretching can provide an aerodynamic advantage. The primary objective of this study was to measure the aerodynamic properties of three commercially available sport fabrics using a standard cylinder methodology over a range of Reynolds numbers and stretch conditions alone with microscopic analysis. The results indicated that the surface texture of the fabric was changed under different stretched levels and these changes in the surface texture had a notable effect on the aerodynamic drag. The surface texture of fabrics caused transitional effect at lower speeds compared to the smooth bare cylinder providing almost 30% drag reduction

A Study on Aerodynamic Drag of a Semi-trailer Truck

AbstractThe primary objective of this study is to determine the aerodynamic impact of various fuel saving devices used in a commercial vehicle (i.e., semi-trailer truck). To measure the aerodynamic drag produced by the vehicle, a wind tunnel study was undertaken using a 1/10th scale model truck. The aerodynamic drags on the baseline vehicle including different external attachments (i.e., front faring, side skirting and gap filling) were measured for a range of vehicle operating speeds and yaw angles, and with different combinations. The results show that these external attachments (fairing and covering) have notable impact on aerodynamic drag as they can reduce up to around 26% aerodynamic drag over the baseline model depending on cross wind effects. The full-skirting (using the front fairing, side skirting and gap filling) has maximum impact whereas only front fairing has minimum impact on aerodynamic drag reduction