Low starting torque is considered as one of the major drawbacks of Darrieus type vertical axis wind turbine (VAWT). Design optimization to overcome this problem by modifying the airfoil geometry has received great attention by the wind energy community. Moreover, efforts have been directed towards augmenting the power coefficient of the turbine. In the present work, the effect of employing slotted airfoil as turbine blade on the performance and starting characteristics has been investigated. The slot parameters; slot location, angle of inclination, and dimensions, were optimized for NACA 0018 airfoil which is commonly used in Darrieus turbines. The flow over the turbine was modelled using ANSYS-FLUENT code. The main observations of the present study show that the VAWT with slotted Airfoil (SA) has a lower optimum tip speed ratio (TSR) compared with the Baseline (BL) turbine. This is associated with the ability to generate higher torque at lower rotational speeds. The analysis of the aerodynamic behavior of the SA turbine shows that the airfoil slot delays the separation at high angles of attack, and therefore improves the torque and power coefficient at low TSR.

Numerical investigation of Darrieus wind turbine with slotted airfoil blades

Effects of trailing-edge movable flap on aerodynamic performance and noise characteristics of VAWT

Computational evaluation of an optimum leading-edge slat deflection angle for dynamic stall control in a novel urban-scale vertical axis wind turbine for low wind speed operation

End of vehicle streamlined head was selected as the installation location, and aerodynamic behavior of trains with and without braking plates was compared to analyze the formation of the braking fo...

https://www.tandfonline.com/doi/pdf/10.1080/19942060.2020.1756414

Comparison of different configurations of aerodynamic braking plate on the flow around a high-speed train

Developments in the design of wind turbines with augmentation are advancing around the globe with the goal of generating electricity close to the user in built-up areas. This is certain to help lessen the power generation load as well as distribution and transmission network costs by reducing the distance between the user and the power source. The main objectives driving the development and advancement of vertical-axis wind turbines are increasing the power coefficient and the torque coefficient by optimizing the upstream wind striking on the rotor blades. Unlike horizontal-axis wind turbines, vertical axis turbines generate not only positive torque but also negative torque during operation. The negative torque generated by the returning blade is a key issue for vertical-axis wind turbines (VAWTs) that is counterproductive. Installation of wind deflectors for flow augmentation helps to reduce the negative torque generated by the returning blades as well as enhance the positive torque by creating a diversion in the upstream wind towards the forwarding blade during operation. This paper reviews various designs, experiments, and CFD simulations of wind deflectors reported to date. Optimization techniques for VAWTs incorporating wind deflectors are discussed in detail. The main focus of the review was on the installation position and orientation of the deflectors and their potential contribution to increasing the power coefficient. Topics for future study are suggested in the conclusion section of the paper.

https://www.mdpi.com/1996-1073/14/16/5140/pdf

Recent Development in the Design of Wind Deflectors for Vertical Axis Wind Turbine: A Review

Effects of leading edge slat on flow separation and aerodynamic performance of wind turbine

Wind energy is a widely used and developed the renewable energy, which has developed rapidly. At present, the design of the horizontal axis wind turbine blade mainly used Blade Element Momentum the...

Numerical optimization of horizontal-axis wind turbine blades with surrogate model:

The reliable folding of proteins is essential for their biological activities, while misfolding may lead to severe diseases, such as Alzheimer’s disease. However, our current knowledge of protein folding arises mainly from studies on small, single-domain proteins rather than multidomain proteins, although the latter make up most of proteins in the cell. Due to complex topological structures and potential interdomain interactions, the refolding of many multidomain proteins often passes through long-lived partially folded intermediates and exhibits complex kinetics. Here, we survey recent progress in understanding the folding and misfolding of multidomain proteins in vitro, with particular reference to theoretical aspects, and briefly summarize the researches on how ribosome regulates folding kinetics of nascent chains during translation in vivo, such as the environmental effects of the ribosome, translation rate effects, and self-interactions effects of polypeptide chain. In addition to these important advances, many questions are still waiting for answer, including: Can a purely structure-based model capture the complex folding kinetics of some multidomain proteins caused by the significant energetic frustration? Is the energy landscape of cotranslational folding still perfectly funnel-like? Are the observed principles that ribosome promotes the proper folding of proteins universal? To what extent does cotranslational folding affect nonnative interactions? Collectively, to address these issues, further innovation and improvement on both experimental techniques and the computational models are in great demand. 

The folding and misfolding mechanisms of multidomain proteins

Laser dry etching using a 248 nm KrF excimer laser was investigated for polydimethylsiloxane (PDMS) chips surface irradiation. Examination of the morphology in relation to ablation depth was emphasized, and a heat conduction model of laser photothermal interaction with PDMS surface was established. The transmittance and absorbance of PDMS at 248nm were validated clearly using UV-vis spectrum measurements. The influence of laser pulse number on the ablation morphology and depth during dry etching was also analyzed. The results showed that with the increase of pulse number, the heat accumulation effect around the etched hole was obvious, and the ablation residue increased. The ablation depth also increased with the pulse number. When the pulse number was 200, the etching depth reached 36.8 μm. This work provides a feasible basis for laser direct etching of PDMS microfluidic chip channels and will promote the development of microfluidic chip fabrication.

Excimer laser dry etching of PDMS applied for microfluidic chips

Laser direct writing technology was a convenient and efficient method in micromachining, which was widely used in polymer processing. In this paper, two kinds of excimer laser (193 nm and 248 nm) were used to irradiate vertically the surface of polydimethylsiloxane (PDMS) for ablation experiments. The experiments were carried out in atmospheric environment, and the ablated samples were characterized by optical microscope, laser confocal microscope, white light interferometer, scanning electron microscope, etc. to obtain their morphology. Analysis was performed on the effects of laser energy and pulse numbers on depth, roughness, and morphology. The outcomes demonstrated that, the crater depth and roughness increased as the number of pulses and energy increased, but that the bottom surface's roughness did not continuously increased with the ablation of a 248 nm laser. At low energy, the roughness remained constant as the number of pulses increased. When the laser operating voltage was adjusted to 23 kV, the roughness increased linearly with the number of pulses. As the laser energy and the number of pulses increased, the number of splashes deposited on the ablation surface increased. Cracks were generally observed across the PDMS surface after a 248 nm laser and the crater edges were rough. The morphology in the 193nm laser ablation showed better micromachining quality, reflected in a small number of pores, sharp edges, and smoother bottom surface.

Study on ablation properties of PDMS by 193 nm and 248 nm excimer laser

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