Computational Analysis of Symmetric and Cambered Blade Darrieus Vertical Axis Wind Turbine With Bio-Mimicked Blade Design

Vertical axis wind turbine suffers from low performance, and the need for improvement is a challenge. This work addresses this problem by using computational fluid dynamics. This chapter aims to analyze and compare symmetric and cambered Darrieus turbine. These analyses are usually carried for straight leading-edge blades, and cambered resembles more the natural shape of the wing of birds and other aquatic mammals, which helps them generate extra lift during movement. Moreover, recent studies suggest better performance was observed for NACA0018 symmetric aerofoil blades, and a similar trend has been observed for NACA2412 cambered aerofoil profiles. Turbine models having symmetric NACA0018 and cambered NACA2412 profiles have been studied. By comparing the symmetric model with cambered blade models, differences in coefficient of torque have been presented. OpenFOAM is used for performing the 2D simulation with dynamicOverset-FvMesh for motion solver with overset mesh method. Meshed geometry was constructed with GMSH codes and the simulation uses overPimpleDyMFoam algorithm as a solver.

Pulsed-flow microchannel heat sink: Simulation and experimental validation

Microchannel heat dissipation devices were first conceptualized in 1981 and since then are at the forefront of cooling techniques for a variety of applications, extending from computer chips and turbine blades to lasers and optical systems. However, much of the research is concentrated on steady flow of a cooling fluid through the channels. In this article, transient two-dimensional (2D) simulation for heat transfer in microchannels under a pulsed-flow condition is carried out. For validation of simulation results, a novel heat sink device is designed and fabricated, using milling and micro-electric discharge machining (EDM) technique. The fabricated device is then tested to evaluate the effect of a variable flow rate on the heat transfer characteristics when the flow is pulsating. It is found that the numerical results underpredict slightly as compared to actual experimental results. Results indicate a higher temperature at the outlet of the heat sink device for lower pulse frequency, and as pulse frequency increases, the outlet temperature decreases.

On the Temperature and Plasma Distribution of an Inductively Driven Xe-I2-Discharge

Inductively Coupled Plasma (ICP) discharges are part of intense research. Predicting different plasma parameters, like the distribution and temperature of the present species, is of great interest for many applications. Iodine- or halide-containing plasmas in particular have an important function, for example, in the development of mercury-free UV radiation sources. Therefore, a 2D simulation model of a xenon- and iodine-containing ICP was created by using the Finite Element Method (FEM) software COMSOL Multiphysics®. The included species and the used reactions are presented in this paper. To verify the simulation in relation to the plasma distribution, the results were compared with measurements from literature. The temperature of the lamp vessel was measured in relation to the temperature distribution and also compared with the results of the simulation. It could be shown that the simulation reproduces the plasma distribution with a maximal deviation of ≈6.5% to the measured values and that the temperature distribution in the examined area can be predicted with deviations of up to ≈24% for long vessel dimensions and ≈3% for shorter dimensions. However, despite the deviating absolute values, the general plasma behaviour is reproduced by the simulation. The simulation thus offers a fast and cost-effective method to estimate an effective geometrical range of iodine-containing ICPs.

Development of a new aerofoil profile with a high lift-to-drag ratio for wind turbines using a low fidelity accurate optimization flow solver

A significant amount of work is performed on various aerofoil profiles to improve their characteristics for wind turbine applications. The main purpose is to increase the power output of wind turbines by increasing the lift-to-drag ratio of the aerofoil blade sections. However, most of the developed aerofoil profiles work well only at their design angles of attack and for low Reynolds numbers with a very dramatic stall that could significantly influence the characteristics of the aerofoil profiles and the performance of wind turbines. The present paper is conducted to develop a new aerofoil profile with more gradual stall characteristics that works efficiently for different operational conditions (clean and rough working conditions) similar to those encountered by wind turbines in the free environment. The new aerofoil profile was developed based on a combination between experimental Box–Behnken design and XFOIL code, measurements, and 2D simulation conducted by computational fluid dynamics (CFD) method. The established aerofoil can be used for wind turbine blades because it gives high lift-to-drag-ratios with very smooth and gradual stall characteristics even under very rough operating conditions.

Evaluation of grain growth exponent by Monte Carlo simulation in polycrystalline materials

In metallurgy, the microstructure study is very important to evaluate the properties and performances of a material. The Monte Carlo method is applied in so many fields of Engineering Science and it is a very effective method to examine the topology of the computer-simulated structures and exactly resembles the static behavior of the atoms. The effective 2D simulation was performed to understand the grain growth kinetics, under the influence of second phase particles (impurities) is a base to control the microstructure. The matrix size and [Formula: see text]-states are optimized. The grain growth exponent was investigated in a polycrystalline material using the [Formula: see text]-state Potts model under the Monte Carlo simulation. The effect of particles present within the belly of grains and pinning on the grain boundaries are observed. The mean grain size under second phase particles obeys the square root dependency.

Improving Energy Performance of Historic Buildings through Hygrothermal Assessment of the Envelope

The intervention on historic buildings through building energy retrofitting has become one of the current challenges of improving energy efficiency. Nonetheless, this building typology presents certain complexities. Among them, one of the most relevant is the protection on their façades due to the historical and/or artistic values of a given façade and, therefore, the addition of external thermal insulation is restricted. However, at the same time, in several of those buildings indoor surfaces do not present that architectural value, and then internal thermal insulation becomes a promising strategy for improving their thermal performance. Nevertheless, its application must be carefully evaluated to avoid possible pathologies caused by moisture problems. This paper aims to identify constructive solutions for interior insulation of walls free from moisture problems. For this purpose, a comprehensive analysis of a series of constructive solutions based on internal insulation has been carried out through hygrothermal simulations. The results show how the application of water-repellent impregnation becomes essential to guaranteeing the integrity of the envelope. In addition, the combination of insulations with or without inner membranes, such as smart vapor retarders or vapor diffusion barriers, has been evaluated detecting the solutions that best fit the objective. Finally, taking advantage of the great potential of 2D simulation tools, the post-processing of the data has been performed to apply the wood decay model, and thus assess the behavior of a very conflictive point in this type of intervention, i.e., the wooden beam-ends. The results in this critical point have shown how the application of the proposed constructive solutions becomes essential to guarantee the integrity of the element and how the application of traditional solutions could lead to a hazard that must be avoided.