scholarly journals Ducted wind turbines in yawed flow: a numerical study

2021 ◽  
Vol 6 (5) ◽  
pp. 1263-1275
Author(s):  
Vinit Dighe ◽  
Dhruv Suri ◽  
Francesco Avallone ◽  
Gerard van Bussel
Keyword(s):  
Wind Turbines ◽  
Urban Areas ◽  
Numerical Study ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Actuator Disc ◽  
Duct Geometry ◽  
Wall Flow ◽  
Yaw Angle ◽  
Surface Discontinuities

Abstract. Ducted wind turbines (DWTs) can be used for energy harvesting in urban areas where non-uniform flows are caused by the presence of buildings or other surface discontinuities. For this reason, the aerodynamic performance of DWTs in yawed-flow conditions must be characterized depending upon their geometric parameters and operating conditions. A numerical study to investigate the characteristics of flow around two DWT configurations using a simplified duct-actuator disc (AD) model is carried out. The analysis shows that the aerodynamic performance of a DWT in yawed flow is dependent on the mutual interactions between the duct and the AD, an interaction that changes with duct geometry. For the two configurations studied, the highly cambered variant of duct configuration returns a gain in performance by approximately 11 % up to a specific yaw angle (α= 17.5∘) when compared to the non-yawed case; thereafter any further increase in yaw angle results in a performance drop. In contrast, performance of less cambered variant duct configuration drops for α>0∘. The gain in the aerodynamic performance is attributed to the additional camber of the duct that acts as a flow-conditioning device and delays duct wall flow separation inside of the duct for a broad range of yaw angles.

scholarly journals Ducted wind turbines in yawed flow: A numerical study

2019 ◽  
Author(s):  
Vinit Dighe ◽  
Dhruv Suri ◽  
Francesco Avallone ◽  
Gerard van Bussel
Keyword(s):  
Wind Turbines ◽  
Urban Areas ◽  
Numerical Study ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Flow Conditions ◽  
Actuator Disc ◽  
Duct Geometry ◽  
Yaw Angle ◽  
Surface Discontinuities

Abstract. Ducted Wind Turbines (DWTs) can be used for energy harvesting in urban areas where non-uniform flows are caused by the presence of buildings or other surface discontinuities. For this reason, the aerodynamic performance of DWTs in yawed flow conditions must be characterized. A numerical study to investigate the characteristics of flow around two DWT configurations using a simplified duct-actuator disc (AD) model is carried out. The analysis shows that the aerodynamic performance of a DWT in yawed flow is dependent on the mutual interaction between the duct and the rotor; an interaction that changes with duct geometry, AD loading and operating conditions. It is found that the duct cross-section camber not only offers insensitivity to yaw, but also a gain in performance up to a specific yaw angle; thereafter any further increase of yaw results in a performance drop.

scholarly journals Multi-element ducts for ducted wind turbines: A numerical study

2019 ◽  
Author(s):  
Vinit V. Dighe ◽  
Francesco Avallone ◽  
Ozer Igra ◽  
Gerard van Bussel
Keyword(s):  
Viscous Flow ◽  
Wind Turbines ◽  
Deflection Angle ◽  
Numerical Study ◽  
Aerodynamic Performance ◽  
Viscous Effects ◽  
Duct Geometry ◽  
Total Thrust ◽  
Flap Deflection ◽  
Radial Gap

Abstract. Multi-element ducts are used to improve the aerodynamic performance of ducted wind turbines (DWTs). Steady-state, two-dimensional computational fluid dynamics (CFD) simulations are performed for a multi-element duct geometry, consisting of a duct and a flap; goal is to evaluate the effects on the aerodynamic performance of the radial gap length and the deflection angle of the flap. Solutions from inviscid and viscous flow calculations are compared. It is found that increasing the radial gap length results in an augmentation of the total thrust generated by the DWT, whereas a larger deflection angle has an opposite effect. A reasonable to good agreement is seen between the inviscid and viscous flow calculations, except for multi-element duct configurations characterized by large flap deflection angles. The viscous effects become stronger at large flap deflection angles, and the inviscid calculations are incapable to take into account this phenomenon.

scholarly journals Multi-element ducts for ducted wind turbines: a numerical study

2019 ◽  
Vol 4 (3) ◽  
pp. 439-449 ◽  
Author(s):  
Vinit V. Dighe ◽  
Francesco Avallone ◽  
Ozer Igra ◽  
Gerard van Bussel
Keyword(s):  
Viscous Flow ◽  
Wind Turbines ◽  
Deflection Angle ◽  
Numerical Study ◽  
Aerodynamic Performance ◽  
Viscous Effects ◽  
Duct Geometry ◽  
Total Thrust ◽  
Flap Deflection ◽  
Radial Gap

Abstract. Multi-element ducts are used to improve the aerodynamic performance of ducted wind turbines (DWTs). Steady-state, two-dimensional computational fluid dynamics (CFD) simulations are performed for a multi-element duct geometry consisting of a duct and a flap; the goal is to evaluate the effects on the aerodynamic performance of the radial gap length and the deflection angle of the flap. Solutions from inviscid and viscous flow calculations are compared. It is found that increasing the radial gap length results in an augmentation of the total thrust generated by the DWT, whereas a larger deflection angle has an opposite effect. Reasonable to good agreement is seen between the inviscid and viscous flow calculations, except for multi-element duct configurations characterized by large flap deflection angles. The viscous effects become stronger at large flap deflection angles, and the inviscid calculations are incapable of taking this phenomenon into account.

scholarly journals Characterization of aerodynamic performance of ducted wind turbines: A numerical study

Wind Energy ◽  
2019 ◽  
Vol 22 (12) ◽  
pp. 1655-1666 ◽  
Author(s):  
Vinit V. Dighe ◽  
Gael Oliveira ◽  
Francesco Avallone ◽  
Gerard J. W. Bussel
Keyword(s):  
Wind Turbines ◽  
Numerical Study ◽  
Aerodynamic Performance

Computational Investigation of a Shrouded Vertical Axis Wind Turbine

2016 ◽  
Author(s):  
K. Vafiadis ◽  
H. Fintikakis ◽  
I. Zaproudis ◽  
A. Tourlidakis
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Urban Areas ◽  
Numerical Study ◽  
Flow Analysis ◽  
Vertical Axis ◽  
Green Energy ◽  
Vertical Axis Wind Turbine ◽  
Wide Range ◽  
Small Wind Turbines

In urban areas, it is preferable to use small wind turbines which may be integrated to a building in order to supply the local grid with green energy. The main drawback of using wind turbines in urban areas is that the air flow is affected by the existence of nearby buildings, which in conjunction with the variation of wind speed, wind direction and turbulence may adversely affect wind energy extraction. Moreover, the efficiency of a wind turbine is limited by the Betz limit. One of the methods developed to increase the efficiency of small wind turbines and to overcome the Betz limit is the introduction of a converging – diverging shroud around the turbine. Several researchers have studied the effect of shrouds on Horizontal Axis Wind Turbines, but relatively little research has been carried out on shroud augmented Vertical Axis Wind Turbines. This paper presents the numerical study of a shrouded Vertical Axis Wind Turbine. A wide range of test cases, were examined in order to predict the flow characteristics around the rotor, through the shroud and through the rotor – shroud arrangement using 3D Computational Fluid Dynamics simulations. The power output of the shrouded rotor has been improved by a factor greater than 2.0. The detailed flow analysis results showed that there is a significant improvement in the performance of the wind turbine.

scholarly journals Aerodynamic Performance Analysis of a Building-Integrated Savonius Turbine

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2636
Author(s):  
Zhaoyong Mao ◽  
Guangyong Yang ◽  
Tianqi Zhang ◽  
Wenlong Tian
Keyword(s):  
Performance Analysis ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
New Technology ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
High Rise ◽  
Turbine Performance ◽  
Cfd Method

The building-integrated wind turbine is a new technology for the utilization of wind energy in cities. Previous studies mainly focused on the wind turbines mounted on the roofs of buildings. This paper discusses the performance of Savonius wind turbines which are mounted on the edges of a high-rise building. A transient CFD method is used to investigate the performance of the turbine and the interaction flows between the turbine and the building. The influence of three main parameters, including the turbine gap, wind angle, and adjacent turbines, are considered. The variations of the turbine torque and power under different operating conditions are evaluated and explained in depth. It is found that the edge-mounted Savonius turbine has a higher coefficient of power than that operating in uniform flows; the average Cp of the turbine under 360-degree wind angles is 92.5% higher than the turbine operating in uniform flows. It is also found that the flow around the building has a great impact on turbine performance, especially when the turbine is located downwind of the building.

scholarly journals Numerical Study of Effect of Sawtooth Riblets on Low-Reynolds-Number Airfoil Flow Characteristic and Aerodynamic Performance

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2102
Author(s):  
Xiaopei Yang ◽  
Jun Wang ◽  
Boyan Jiang ◽  
Zhi’ang Li ◽  
Qianhao Xiao
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Numerical Study ◽  
Low Reynolds Number ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Viscous Drag ◽  
Airfoil Flow ◽  
Low Reynolds ◽  
Reduction Effect

Riblets with an appropriate size can effectively restrain turbulent boundary layer thickness and reduce viscous drag, but the effects of riblets strongly depend on the appearance of the fabric that is to be applied and its operating conditions. In this study, in order to improve the aerodynamic performance of a low-pressure fan by using riblet technology, sawtooth riblets on NACA4412 airfoil are examined at the low Reynolds number of 1 × 105, and the airfoil is operated at angles of attack (AOAs) ranging from approximately 0° to 12°. The numerical simulation is carried out by employing the SST k–ω turbulence model through the Ansys Fluent, and the effects of the riblets’ length and height on aerodynamic performance and flow characteristics of the airfoil are investigated. The results indicate that the amount of drag reduction varies greatly with riblet length and height and the AOA of airfoil flow. By contrast, the riblets are detrimental to the airfoil in some cases. The most effective riblet length is found to be a length of 0.8 chord, which increases the lift and reduces the drag under whole AOA conditions, and the maximum improvements in both are 17.46% and 15.04%, respectively. The most effective height for the riblet with the length of 0.5 chord is 0.6 mm. This also improves the aerodynamic performance and achieves a change rate of 12.67% and 14.8% in the lift and drag coefficients, respectively. In addition, the riblets facilitate a greater improvement in airfoil at larger AOAs. The flow fields demonstrate that the riblets with a drag reduction effect form “the antifriction-bearing” structure near the airfoil surface and effectively restrain the trailing separation vortex. The ultimate cause of the riblet drag reduction effect is the velocity gradient at the bottom of the boundary layers being increased by the riblets, which results in a decrease in boundary thickness and energy loss.

Through-Building Ducts for Mounting Wind Turbines: A Numerical Study

2021 ◽  
Author(s):  
Hadi Mirian ◽  
Morteza Anbarsooz ◽  
Abbas Hoshyar ◽  
Alireza ArabGolarcheh
Keyword(s):  
Wind Turbine ◽  
Wind Power ◽  
Wind Turbines ◽  
Pressure Difference ◽  
Urban Areas ◽  
High Speed ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Maximum Velocity ◽  
Maximum Pressure

Abstract Yet, several locations for mounting the wind turbines in urban areas have been proposed, which can be categorized into four main groups; (a) on the rooftops, (b) between the buildings, (c) integrated into the buildings’ skin and (d) inside a though-building hole. Through-building holes take advantage of the pressure difference between the windward and leeward facades of the building to generate a high-speed velocity zone for mounting the wind turbine. In the current study, three-dimensional numerical simulations of atmospheric turbulent boundary layer flow around high-rise buildings are carried out to determine the optimum location and size of the duct. For this purpose, square cross-section buildings (20 × 20 m) with heights of H0 = 60, 120 and 180 m are considered. Numerical results showed that the difference of the pressure coefficient on the windward and leeward facades of the building without the hole can predict the best location for mounting the wind turbine with acceptable accuracy. Then, circular holes with various diameters of D = 2.5, 5.0, 7.5, 10 and 12.5m are created at z/H0 = 0.8, where the maximum pressure difference is close to the maximum. It is found that the maximum velocity increment occurs for D = 10 m and it is 31% greater than the U10 velocity of the incident wind profile. This means that the available wind power inside the duct is 2.25 times greater than the incident wind power.

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