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1 – 10 of over 3000Mehran Masdari, Milad Mousavi and Mojtaba Tahani
One of the best methods to improve wind turbine aerodynamic performance is modification of the blade’s airfoil. The purpose of this paper is to investigate the effects of gurney…
Abstract
Purpose
One of the best methods to improve wind turbine aerodynamic performance is modification of the blade’s airfoil. The purpose of this paper is to investigate the effects of gurney flap geometry and its oscillation parameters on the pitching NACA0012 airfoil.
Design/methodology/approach
This numerical solution has been carried out for different cases of gurney flap mounting angles, heights, reduced frequencies and oscillation amplitudes, then the results were compared to each other. The finite volume method was used for the discretization of the governing equations, and the PISO algorithm was used to solve the equations. Also, the “SST” was adopted as the turbulence model in the simulation.
Findings
In this paper, the different parameters of gurney flap were investigated. The results showed that the best range of gurney flap height are between 1 and 3.2% of chord and the best ratio of lifting to drag coefficient is achieved in gurney flap with an angle of 90° relative to the chord direction. The dynamic stall angle of the airfoil with gurney flap decreases were compared to without gurney flap. Earlier LEV formation can be one of the main reasons for decreasing the dynamic stall angle of the airfoil with gurney flap. Increasing the reduced frequency and oscillation amplitude causes rising of maximum lift coefficient and consequently lift curve slope. Moreover, gurney flap with mounting angle has a lower hinge moment than the gurney flap without mounting angle but with the same vertical axis length. So, there is more complexity in structural design concerning the gurney flap without mounting angle.
Practical implications
Improving aerodynamic efficiency of airfoils is vital for obtaining more output power in VAWTs. Gurney flaps are one of the best mechanisms to increase the aerodynamic performance of the airfoil and increases the efficiency of VAWTs.
Originality/value
Investigating the hinge moment on the connection point of the airfoil, gurney flap and try to compare the gurney flap with and without angle.
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Hashwini Lalchand Thadani, Fadia Dyni Zaaba, Muhammad Raimi Mohammad Shahrizal, Arjun Singh Jaj A. Jaspal Singh Jaj and Yun Ii Go
This paper aims to design an optimum vertical axis wind turbine (VAWT) and assess its techno-economic performance for wind energy harvesting at high-speed railway in Malaysia.
Abstract
Purpose
This paper aims to design an optimum vertical axis wind turbine (VAWT) and assess its techno-economic performance for wind energy harvesting at high-speed railway in Malaysia.
Design/methodology/approach
This project adopted AutoCAD and ANSYS modeling tools to design and optimize the blade of the turbine. The site selected has a railway of 30 km with six stops. The vertical turbines are placed 1 m apart from each other considering the optimum tip speed ratio. The power produced and net present value had been analyzed to evaluate its techno-economic viability.
Findings
Computational fluid dynamics (CFD) analysis of National Advisory Committee for Aeronautics (NACA) 0020 blade has been carried out. For a turbine with wind speed of 50 m/s and swept area of 8 m2, the power generated is 245 kW. For eight trains that operate for 19 h/day with an interval of 30 min in nonpeak hours and 15 min in peak hours, total energy generated is 66 MWh/day. The average cost saved by the train stations is RM 16.7 mil/year with battery charging capacity of 12 h/day.
Originality/value
Wind energy harvesting is not commonly used in Malaysia due to its low wind speed ranging from 1.5 to 4.5 m/s. Conventional wind turbine requires a minimum cut-in wind speed of 11 m/s to overcome the inertia and starts generating power. Hence, this paper proposes an optimum design of VAWT to harvest an unconventional untapped wind sources from railway. The research finding complements the alternate energy harvesting technologies which can serve as reference for countries which experienced similar geographic constraints.
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Ahmed Benamor, Aissa Abidi-Saad, Ridha Mebrouk and Sarra Fatnassi
This study aims at investigating two-dimensional laminar flow of power-law fluids around three unconfined side-by-side cylinders.
Abstract
Purpose
This study aims at investigating two-dimensional laminar flow of power-law fluids around three unconfined side-by-side cylinders.
Design/methodology/approach
The numerical study is performed by solving the governing (continuity and momentum) equations using a finite volume-based code ANSYS Fluent. The numerical results have been presented for different combinations of the governing dimensionless parameters (dimensionless spacing, 1.2 = L = 4; Reynolds number, 0.1 = Re = 100; power-law index, 0.2 = n = 1.8). The dependence of the kinematic and macroscopic characteristics of the flow such as streamline patterns, distribution of the surface pressure coefficient, total drag coefficient with its components (pressure and friction) and total lift coefficient on these dimensionless parameters has been discussed in detail.
Findings
It is found that the separation of the flow and the apparition of the wake region accelerate as the dimensionless spacing decreases, the number of the cylinder increases and/or the fluid behavior moves from shear-thinning to Newtonian then to shear-thickening behavior. In addition, the distribution of the pressure coefficient on the surface of the cylinders presents a complex dependence on the fluid behavior index and Reynolds number when the dimensionless spacing between two adjacent cylinders is varied. At low Reynolds numbers, the drag coefficient of shear-thinning fluids is stronger than that of Newtonian fluids; this tendency decreases progressively with increasing of Re until a critical value; beyond the critical Re, the opposite trend is observed. The lift coefficient of the middle cylinder is null, whereas, the exterior cylinders experience opposite lift coefficients, which show a complex dependence on the dimensionless spacing, the Reynolds number and the power-law index.
Originality/value
The flow over bluff bodies is a practical engineering problem. In the literature, it can be seen that the previous studies on non-Newtonian fluids are limited to the flow over one or two cylinders (effect of an odd number of cylinders on each other). Besides that, the available results concerning the flow of Newtonian fluids over three cylinders are limited to the high Reynolds numbers region only. However, this work treats the flow of non-Newtonian power-law fluids past three circular cylinders in side-by-side arrangements under a wide range of Re. The outcome of the present study demonstrates that the augmentation of the geometry complexity to three cylinders (effect of pair surrounding cylinders on the surrounded ones in what concerns Von Karman Street phenomenon) causes a drastic change in the flow patterns and in the macroscopic characteristics. The present results may be used to predict the flow behavior around multiple side-by-side cylinders.
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Md Motiur Rahaman, Nirmalendu Biswas, Apurba Kumar Santra and Nirmal K. Manna
This study aims to delve into the coupled mixed convective heat transport process within a grooved channel cavity using CuO-water nanofluid and an inclined magnetic field. The…
Abstract
Purpose
This study aims to delve into the coupled mixed convective heat transport process within a grooved channel cavity using CuO-water nanofluid and an inclined magnetic field. The cavity undergoes isothermal heating from the bottom, with variations in the positions of heated walls across the grooved channel. The aim is to assess the impact of heater positions on thermal performance and identify the most effective configuration.
Design/methodology/approach
Numerical solutions to the evolved transport equations are obtained using a finite volume method-based indigenous solver. The dimensionless parameters of Reynolds number (1 ≤ Re ≤ 500), Richardson number (0.1 ≤ Ri ≤ 100), Hartmann number (0 ≤ Ha ≤ 70) and magnetic field inclination angle (0° ≤ γ ≤ 180°) are considered. The solved variables generate both local and global variables after discretization using the semi-implicit method for pressure linked equations algorithm on nonuniform grids.
Findings
The study reveals that optimal heat transfer occurs when the heater is positioned at the right corner of the grooved cavity. Heat transfer augmentation ranges from 0.5% to 168.53% for Re = 50 to 300 compared to the bottom-heated case. The magnetic field’s orientation significantly influences the average heat transfer, initially rising and then declining with increasing inclination angle. Overall, this analysis underscores the effectiveness of heater positions in achieving superior thermal performance in a grooved channel cavity.
Research limitations/implications
This concept can be extended to explore enhanced thermal performance under various thermal boundary conditions, considering wall curvature effects, different geometry orientations and the presence of porous structures, either numerically or experimentally.
Practical implications
The findings are applicable across diverse fields, including biomedical systems, heat exchanging devices, electronic cooling systems, food processing, drying processes, crystallization, mixing processes and beyond.
Originality/value
This work provides a novel exploration of CuO-water nanofluid flow in mixed convection within a grooved channel cavity under the influence of an inclined magnetic field. The influence of different heater positions on thermomagnetic convection in such a cavity has not been extensively investigated before, contributing to the originality and value of this research.
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Shian Li, Gongnan Xie and Bengt Sunden
The employment of continuous ribs in a passage involves a noticeable pressure drop penalty, while other studies have shown that truncated ribs may provide a potential to reduce…
Abstract
Purpose
The employment of continuous ribs in a passage involves a noticeable pressure drop penalty, while other studies have shown that truncated ribs may provide a potential to reduce the pressure drop while keeping a significant heat transfer enhancement. The purpose of this paper is to perform computer-aided simulations of turbulent flow and heat transfer of a rectangular cooling passage with continuous or truncated 45-deg V-shaped ribs on opposite walls.
Design/methodology/approach
Computational fluid dynamics technique is used to study the fluid flow and heat transfer characteristics in a three-dimensional rectangular passage with continuous and truncated V-shaped ribs.
Findings
The inlet Reynolds number, based on the hydraulic diameter, is ranged from 12,000 to 60,000 and a low-Re k-e model is selected for the turbulent computations. The local flow structure and heat transfer in the internal cooling passages are presented and the thermal performances of the ribbed passages are compared. It is found that the passage with truncated V-shaped ribs on opposite walls provides nearly equivalent heat transfer enhancement with a lower (about 17 percent at high Reynolds number of 60,000) pressure loss compared to a passage with continuous V-shaped ribs or continuous transversal ribs.
Research limitations/implications
The fluid is incompressible with constant thermophysical properties and the flow is steady. The passage is stationary.
Practical implications
New and additional data will be helpful in the design of ribbed passages to achieve a good thermal performance.
Originality/value
The results imply that truncated V-shaped ribs are very effective in improving the thermal performance and thus are suggested to be applied in gas turbine blade internal cooling, especially at high velocity or Reynolds number.
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Caroline C. Sullivan, Audrey Schewe, Emily Juckett and Heather Stevens
Effective discussion is inextricably linked to democracy. Social studies curriculum and instruction should engage students in practicing democratic skills and habits of mind. This…
Abstract
Effective discussion is inextricably linked to democracy. Social studies curriculum and instruction should engage students in practicing democratic skills and habits of mind. This case study provides a microanalysis of one U.S. History teacher’s commitment to fostering discussion in her classroom as a theorized pedagogical practice. A better understanding of what motivates teachers to engage students in classroom discussions paralleled with rich descriptions of how this teacher plans and implements discussion could encourage others to try this approach to teaching and learning.
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This study aims to present a numerical analysis of the behavior of the electric field and flow field characteristics under electrohydrodynamics (EHD) force. The influence of the…
Abstract
Purpose
This study aims to present a numerical analysis of the behavior of the electric field and flow field characteristics under electrohydrodynamics (EHD) force. The influence of the jet airflow under the EHD force is investigated when it impacts the inclined flat plate.
Design/methodology/approach
The high electrical voltage and angle of an inclined flat plate are tested in a range of 0–30 kV and 0–90°, respectively. In this condition, the air is set in a porous medium and the inlet jet airflow is varied from 0–2 m/s.
Findings
The results of this study show that the electric field line patterns increase with increasing the electrical voltage and it affects the electric force increasing. The angle of inclined flat plate and the boundary of the computational model are influenced by the electric field line patterns and electrical voltage surface. The electric field pattern is the difference in the fluid flow pattern. The fluid flow is more expanded and more concentrated with increasing the angle of an inclined flat plate, the electrical voltage and the inlet jet airflow. The velocity field ratio is increased with increasing the electrical voltage but it is decreased with increasing the angle of the inclined flat plate and the inlet jet airflow.
Originality/value
The maximum Reynolds number, the maximum velocity field and the maximum cell Reynolds number are increased with increasing the electrical voltage, the inlet jet airflow and the angle of the inclined flat plate. In addition, the cell Reynolds number characteristics are more concentrated and more expanded with increasing the electrical voltage. The pattern of numerical results from the cell Reynolds number characteristics is similar to the pattern of the fluid flow characteristics. Finally, a similar trend of the maximum velocity field has appeared for experimental and numerical results so both techniques are in good agreement.
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Jacques Abou Khalil, César Jiménez Navarro, Rami El Jeaid, Abderahmane Marouf, Rajaa El Akoury, Yannick Hoarau, Jean-François Rouchon and Marianna Braza
This study aims to investigate the morphing concepts able to manipulate the dynamics of the downstream unsteadiness in the separated shear layers and, in the wake, be able to…
Abstract
Purpose
This study aims to investigate the morphing concepts able to manipulate the dynamics of the downstream unsteadiness in the separated shear layers and, in the wake, be able to modify the upstream shock–boundary layer interaction (SBLI) around an A320 morphing prototype to control these instabilities, with emphasis to the attenuation or even suppression of the transonic buffet. The modification of the aerodynamic performances according to a large parametric study carried out at Reynolds number of 4.5 × 106, Mach number of 0.78 and various angles of attack in the range of (0, 2.4)° according to two morphing concepts (travelling waves and trailing edge vibration) are discussed, and the final benefits in aerodynamic performance increase are evaluated.
Design/methodology/approach
This article examines through high fidelity (Hi-Fi) numerical simulation the effects of the trailing edge (TE) actuation and of travelling waves along a specific area of the suction side starting from practically the most downstream position of the shock wave motion according to the buffet and extending up to nearly the TE. The present paper studies through spectral analysis the coherent structures development in the near wake and the comparison of the aerodynamic forces to the non-actuated case. Thus, the physical mechanisms of the morphing leading to the increase of the lift-to-drag ratio and the drag and noise sources reduction are identified.
Findings
This study investigates the influence of shear-layer and near-wake vortices on the SBLI around an A320 aerofoil and attenuation of the related instabilities thanks to novel morphing: travelling waves generated along the suction side and trailing-edge vibration. A drag reduction of 14% and a lift-to-drag increase in the order of 8% are obtained. The morphing has shown a lift increase in the range of (1.8, 2.5)% for angle of attack of 1.8° and 2.4°, where a significant lift increase of 7.7% is obtained for the angle of incidence of 0° with a drag reduction of 3.66% yielding an aerodynamic efficiency of 11.8%.
Originality/value
This paper presents results of morphing A320 aerofoil, with a chord of 70cm and subjected to two actuation kinds, original in the state of the art at M = 0.78 and Re = 4.5 million. These Hi-Fi simulations are rather rare; a majority of existing ones concern smaller dimensions. This study showed for the first time a modified buffet mode, displaying periodic high-lift “plateaus” interspersed by shorter lift-decrease intervals. Through trailing-edge vibration, this pattern is modified towards a sinusoidal-like buffet, with a considerable amplitude decrease. Lock-in of buffet frequency to the actuation is obtained, leading to this amplitude reduction and a drastic aerodynamic performance increase.
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Fariborz Karimi Talkhoncheh, Hongtao Xu, Zhiyun Wang, Mo Yang and Yuwen Zhang
– Unsteady simulation of forced convection of two heated horizontal cylinders confined in a 2D squared enclosure. The paper aims to discuss this issue.
Abstract
Purpose
Unsteady simulation of forced convection of two heated horizontal cylinders confined in a 2D squared enclosure. The paper aims to discuss this issue.
Design/methodology/approach
The finite-volume method is used to solve the transient heat transfer problem by employing quadrilateral mesh type. To solve the governing equations (conservations of mass, momentum and energy) on unstructured control volumes, a second-order quadratic upwind interpolation of convective kinematics scheme for the convection terms and the semi-implicit method for pressure-linked equations pressure correction algorithm were used.
Findings
The results indicate that the variation of the area-averaged Nusselt number strongly depends on the Reynolds number. On the contrary, the effect of cylinders’ space on heat transfer was found to be nearly negligible for Re < 460. It is also observed that steady state flow and heat transfer shift to periodical oscillation, and ultimately chaotic oscillation in non-dimensional cylinders distance of 0.1; however the sequence of appearing this route is completely different for higher cylinder spaces.
Research limitations/implications
Reynolds numbers between 380 and 550 and dimensionless horizontal distances of cylinders 0.1, 0.2 and 0.3.
Originality/value
Comprehensive knowledge of the effect of tube arrays flow regime on each other and in turn, heat transfer among them. Better understanding of convective heat transfer around an array of horizontal cylinders compared with from those around a single cylinder because of the mutual interaction of the buoyant plumes generated by the cylinders. Time-dependent phenomena of the problem including periodical oscillation or chaotic features.
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BIJAN FARHANIEH and BENGT SUNDÉN
Laminar fully developed periodic heat transfer and fluid flow characteristics in corrugated two‐dimensional ducts with constant cross‐sectional area are numerically investigated…
Abstract
Laminar fully developed periodic heat transfer and fluid flow characteristics in corrugated two‐dimensional ducts with constant cross‐sectional area are numerically investigated. The governing equations are solved numerically by a finite‐volume method for elliptic flows in complex geometries using colocated variables and Cartesian velocity components. The results were obtained for a uniform wall temperature for two inclination angles and three duct aspect ratios (H/L) and for Reynolds number ranging from 30 to 1200. The plot of the velocity vectors show a complex flow pattern. Unexpected high enhancement of the average Nusselt number was observed at low Reynolds number for H/L = ½ and ⅓. A moderate increase in Nusselt number was obtained as Reynolds number was increased further.
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