scholarly journals Numerical Investigations of the Savonius Turbine with Deformable Blades

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3717 ◽  
Author(s):  
Krzysztof Sobczak ◽  
Damian Obidowski ◽  
Piotr Reorowicz ◽  
Emil Marchewka
Keyword(s):  
Wind Direction ◽  
Solid Mechanics ◽  
Transient Flow ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Power Coefficient ◽  
Noise Emission ◽  
Computational Fluid Dynamics Cfd ◽  
Low Efficiency ◽  
Computational Solid Mechanics

Savonius wind turbines are characterized by various advantages such as simple design, independence of wind direction, and low noise emission, but they suffer from low efficiency. Numerous investigations were carried out to face this problem. In the present paper, a new idea of the Savonius turbine with a variable geometry of blades is proposed. Its blades, made of elastic material, were continuously deformed during the rotor revolution to increase a positive torque of the advancing blade and to decrease a negative torque of the returning blade. In order to assess the turbine aerodynamic performance, a two-dimensional numerical model was developed. The fluid-structure interaction (FSI) method was applied where blade deformations were defined by computational solid mechanics (CSM) simulations, whereas computational fluid dynamics (CFD) simulations allowed for transient flow prediction. The influence of the deformation magnitude and the position of maximally deformed blades with respect to the incoming wind direction were studied. The aerodynamic performance increased with an increase in the deformation magnitude. The power coefficient exceeded Cp = 0.30 for the eccentricity magnitude of 10% and reached 0.39 for the highest magnitude under study. It corresponded to 90% improvement in comparison to Cp = 0.21 in the case of the fixed-shape Savonius turbine.

scholarly journals Preliminary Performance Tests and Simulation of a V-Shape Roof Guide Vane Mounted on an Eco-Roof System

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2846 ◽  
Author(s):  
Xiaohang Wang ◽  
Wentong Chong ◽  
Kokhoe Wong ◽  
Liphuat Saw ◽  
Sinchew Poh ◽  
...  
Keyword(s):  
Power Generation ◽  
Guide Vane ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Roof System ◽  
Low Wind Speed ◽  
Computational Fluid Dynamics Cfd ◽  
Power Generation System ◽  
Low Efficiency

The technical and economic features of a patented V-shape roof guide vane (VRGV) with a solar and wind power generation system mounted on an eco-roof system are presented in this paper. Moreover, this innovative VRGV was investigated on for the purpose of improving the performance of a vertical axis wind turbine (VAWT), which was installed on an eco-roof system to solve the low-efficiency power generation problem of the wind turbines under the condition of a low wind speed. This paper proposes a preliminary study for the performance of the VAWT with the VRGV on a building. This research used a mock-up building with a double slope roof, where a five straight-bladed VAWT was mounted and tested under two conditions, with and without the VRGV. From the comparative experiments, the self-starting performance and rotational speed of the VAWT mounted above a double slope roof with the VRGV have been significantly improved compared to the VAWT without the VRGV. Further, the power coefficient (Cp) of the VAWT can be augmented to about 71.2% increment due to the VRGV design. In addition, numerical simulations by computational fluid dynamics (CFD) were proposed to verify the augmented effect of the Cp of the VAWT under the influence of the VRGV in the experiment. Besides, economic estimation of the VRGV was conducted.

Effect of the Number of Stages on the Performance of Savonius Vertical Axis Wind Turbines: Part II — Using Twisted Blades

2020 ◽  
Author(s):  
Ahmed S. Saad ◽  
Shinichi Ookawara ◽  
Ahmed Elwardany ◽  
Ibrahim I. El-Sharkawy ◽  
Mahmoud Ahmed
Keyword(s):  
Phase Angle ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Single Stage ◽  
Power Coefficient ◽  
Two Stage ◽  
Savonius Rotor ◽  
Vertical Axis Wind Turbines

Abstract Wind energy comprises one of several renewable resources of energy engineered to contain the global energy crisis. Although horizontal axis wind turbines (HAWTs) have proven to be effective in low turbulence and steady wind conditions, vertical axis wind turbines (VAWTs) potentially have the advantage in highly variable and turbulent regions. The Savonius vertical axis wind turbine has several advantages such as simple design, low manufacturing costs, low operating wind speed, low noise, and Omni-directional capability. However, the Savonius rotor requires further design optimization to improve its aerodynamic performance before becoming competitive with other turbine designs. Thus, the main objective of the current study is to numerically investigate the aerodynamic performance of a multistage Savonius rotor to enhance the power coefficient and the ability of self-starting. In the current study, one-, two-, three-, and four-stage Savonius rotors with twisted blades are investigated. In a two-stage rotor, one single-stage rotor is mounted over another single-stage with a phase angle of 90°. In a three-stage rotor, the three single-stage rotors are mounted one above the other with a phase angle of 60° relative to one another while with a phase angle of 45° for the four stage-rotor. The blades of the studied Savonius rotor are twisted with a twist angle (φ) of 45°. This is the first contribution to understand how multi-stages influence the aerodynamic performance of the twisted-bladed Savonius rotor. Moreover, variations of torque and power coefficients are computed for all the studied rotors with various numbers of stages. The developed numerical model is simulated using ANSYS Fluent and validated using the available experimental and numerical results. Results showed that the coefficients of torque (CT) and power (CP) increase with rising the number of stages. Increasing the number of stages from 1 to 2 significantly increases the CT and CP of the rotor. However, with a further increase in the number of stages to 3 and 4 stages, both the CT and CP remains almost the same as the rotor with 2 stages. The maximum coefficient of torque (CT, max) and power (CP, max) for a two-stage rotor are 0.42 and 0.253, respectively. The gain in the coefficient of power obtained by using the two-stage Savonius rotor with twisted blades is 53.5% compared to the conventional single-stage which has a coefficient of power 0.165 at a wind velocity of 6 m/s. Moreover, using multi-stages and twisted blades significantly smooth the variations in the generated torque and produce positive values at all rotor angles resulted in improving the self-starting ability of the Savonius rotor.

Development of a New Design Method for High Efficiency Swept Low Pressure Axial Fans With Small Hub/Tip Ratio

2014 ◽  
Author(s):  
Thore Bastian Lindemann ◽  
Jens Friedrichs ◽  
Udo Stark
Keyword(s):  
High Efficiency ◽  
Design Method ◽  
Tangential Velocity ◽  
Pressure Rise ◽  
Low Pressure ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Angle Distribution ◽  
Sweep Angle ◽  
Reduced Pressure

For a competitive low pressure axial fan design low noise emission is as important as high efficiency. In this paper a new design method for low pressure fans with a small hub to tip ratio including blade sweep is introduced and discussed based on experimental investigations. Basis is an empirical axial and tangential velocity distribution at the rotor outlet combined with a distinctive sweep angle distribution along the stacking line. Several fans were designed, built and tested in order to analyze the aerodynamic as well as the aeroacoustic behavior. For the aerodynamic performance particular attention was paid to compensate the influence of reduced pressure rise and efficiency due to increasing blade sweep. This was achieved by a method of increasing the blade chord depending on the local sweep angle which is based on single airfoil data. The tested fans without this compensation revealed a significant noise reduction effect of up to approx. 6 dB(A) for a tip sweep angle of 64° which was accompanied by an unsatisfactory effect of reduced overall aerodynamic performance. The second group of fans did not only confirm the method of the aerodynamic compensation by a nearly unchanged pressure rise and efficiency characteristic but also revealed an increased aeroacoustic benefit of in average 9.5 dB(A) compared to the unswept version. Beside the overall characteristics the individual differences between the designs are also discussed using results of wall pressure measurements which show some significant changes of the blade tip flow structure.

scholarly journals DEUFRABASE: A Simple Tool for the Evaluation of the Noise Impact of Pavements in Typical Road Geometries

Environments ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. 27 ◽  
Author(s):  
Michel Bérengier ◽  
Judicaël Picaut ◽  
Bettina Pahl ◽  
Denis Duhamel ◽  
Benoit Gauvreau ◽  
...  
Keyword(s):  
Traffic Noise ◽  
Emission Spectra ◽  
Low Noise ◽  
Noise Emission ◽  
Simple Method ◽  
Acceptable Error ◽  
The Road ◽  
Noise Impact ◽  
On The Road ◽  
The Impact

Traffic noise is considered by people as one of the most important sources of environmental discomfort. A way to limit the traffic noise is to reduce the noise emission, for example, by using specific low noise pavements, particularly in suburban areas. However, in real situations, it can be difficult to evaluate the impact of a given pavement, because it depends, for example, on the road geometry, the meteorological conditions, or the distance of the receiver position. Finally it can be difficult to select the most appropriate pavement for a given noise reduction objective. In this paper, a simple method is proposed to evaluate the noise impact of a pavement, in typical road geometries and environmental conditions. The proposed approach uses two databases, the first one based on measurements of emission spectra of road vehicles on several typical pavements, the second one made of pre-calculations of noise propagation for typical road configurations. Finally, the method is implemented in an interactive web tool, called DEUFRABASE, which allows one to obtain a fast estimation of the L Aeq (1 h or 24 h) and L den noise levels for various pavements and road configurations, as functions of the traffic flow and composition. By comparing the method with measurements, it is showed that the tool, although based on a restricted number of pavements and on several simplifications, can predict the noise impact of typical road configurations, with an acceptable error, most often less than 2 dB.

Expansion joints with low noise emission

2008 ◽  
pp. 51-52
Author(s):  
C O’Suilleabhain ◽  
G Moor ◽  
T Spuler
Keyword(s):  
Low Noise ◽  
Noise Emission ◽  
Expansion Joints

URANS Simulations and Experimental Investigations on Unsteady Aerodynamic Effects in the Blade Tip Region of a Shrouded Fan Configuration

2017 ◽  
Author(s):  
Gi-Don Na ◽  
Frank Kameier ◽  
Nils Springer ◽  
Michael Mauß ◽  
C. O. Paschereit
Keyword(s):  
Applied Sciences ◽  
Numerical Simulations ◽  
Aerodynamic Performance ◽  
Design Parameters ◽  
Experimental Investigations ◽  
Acoustic Measurements ◽  
Noise Emission ◽  
Industrial Partner ◽  
University Of Applied Sciences ◽  
Blade Tip

The acoustical characteristics of cooling fans are an essential criterion of product quality in the automotive industry. Fan modules have to suffice growing customer expectations which are reflected in the comfort requirements set by car manufacturers around the world. In order to locate dominant acoustic sources and to reduce the noise emission generated by a shrouded fan configuration, numerical simulations and experimental investigations are performed. The working approach considers variously modified fan geometries and their evaluation regarding arising vortex flow phenomena and their effect on a decreased sound pressure level (SPL) in consideration of an improvement or the constancy of aerodynamic fan performance. Particular emphasis lies on the analysis of secondary flows in the blade tip region by post-processing CFD-results. Due to the large number of geometrical modifications investigated and the importance of highly resolved eddy structures, a hybrid approach is chosen by applying the SAS-SST turbulence model in URANS simulations. The SAS (Scale Adaptive Simulation) delivers LES (Large Eddy Simulation) content in unsteady regions of a RANS-simulation and exhibits not nearly the high computational effort needed to perform a full scale LES. An assessment of the actual propagation of noise emission into the far-field is made by performing experimental investigations on the most promising modifications. The acoustic measurements are carried out in a fan test stand in the anechoic chamber of Duesseldorf University of Applied Sciences. The aerodynamic performance is measured in a fan test rig with an inlet chamber setup in accordance to ISO 5801. The measured acoustical and aerodynamic performances are validated by the industrial partner. The results of the acoustic measurements are in turn utilized to determine indicators of noise radiation in the numerical simulation. Within this work an innovative geometry modification is presented which can be implemented into shrouded fan configurations with backward-skewed blades. The new design exhibits a reduced SPL (A-weighted) of approx. 4 dB over the entire operating range while showing no significant deterioration on the aerodynamic performance. While the design was registered for patent approval cooperatively by the industrial partner and Duesseldorf University of Applied Sciences, further investigations regarding variations of design parameters are performed and presented in this paper. All numerical simulations are performed with ANSYS CFX, a commercial solver widely spread in the industry. Methods similar to those shown in this work can be implemented in the design phase of axial fans in order to develop acoustically optimized fan geometries.

scholarly journals Influence of Wind Speed, Wind Direction and Turbulence Model for Bridge Hanger: A Case Study

Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1633
Author(s):  
Yang Ding ◽  
Shuang-Xi Zhou ◽  
Yong-Qi Wei ◽  
Tong-Lin Yang ◽  
Jing-Liang Dong
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Wind Field ◽  
Solid Mechanics ◽  
Von Mises Stress ◽  
Long Span Bridges ◽  
High Rise ◽  
Long Span ◽  
Cfd Models ◽  
Von Mises

Wind field (e.g., wind speed and wind direction) has the characteristics of randomness, nonlinearity, and uncertainty, which can be critical and even destructive on a long-span bridge’s hangers, such as vortex shedding, galloping, and flutter. Nowadays, the finite element method is widely used for model calculation, such as in long-span bridges and high-rise buildings. In this study, the investigated bridge hanger model was established by COMSOL Multiphysics software, which can calculate fluid dynamics (CFD), solid mechanics, and fluid–solid coupling. Regarding the wind field of bridge hangers, the influence of CFD models, wind speed, and wind direction are investigated. Specifically, the bridge hanger structure has symmetrical characteristics, which can greatly reduce the calculation efficiency. Furthermore, the von Mises stress of bridge hangers is calculated based on fluid–solid coupling.

scholarly journals Double multiple stream tube theory coupled with dynamic stall and wake correction for aerodynamic investigation of vertical axis wind turbine

2020 ◽  
Vol 23 (4) ◽  
pp. 771-780
Author(s):  
Anh Ngoc VU ◽  
Ngoc Son Pham
Keyword(s):  
Wind Turbine ◽  
Shape Function ◽  
Vertical Axis ◽  
Transformation Method ◽  
Aerodynamic Performance ◽  
Dynamic Stall ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Stream Tube ◽  
Aerodynamic Investigation

This study describes an effectively analytic methodology to investigate the aerodynamic performance of H vertical axis wind turbine (H-VAWT). An in-house code based on double multiple stream tube theory (DMST) coupled with dynamic stall and wake correction is implemented to estimate the power coefficient. Design optimization of airfoil shape is conducted to study the influences of the dynamic stall and turbulent wakes. Airfoil shape is universally investigated by using the Class/Shape function transformation method. The airfoil study shows that the upper curve tends to be less convex than the lower curve in order to extract more energy of the wind upstream and generate less drag of the blade downstream. The optimal results show that the power coefficient increases by 6.5% with the new airfoil shape.

Optimized Small Vertical Axis Wind Turbine (VAWT), Phase I

2021 ◽  
Author(s):  
Moshe Zilberman ◽  
Abdelaziz Abu Sbaih ◽  
Ibrahim Hadad
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Cost Effective ◽  
Clean Energy ◽  
Vertical Axis ◽  
Low Noise ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Different Types

Abstract Wind energy has become an important resource for the growing demand for clean energy. In 2020 wind energy provided more than 6% of the global electricity demand. It is expected to reach 7% at the end of 2021. The installation growth rate of small wind turbines, though, is relatively slow. The reasons we are interested in the small vertical axis wind turbines are their low noise, environmentally friendly, low installation cost, and capable of being rooftop-mounted. The main goal of the present study is an optimization process towards achieving the optimal cost-effective vertical wind turbine. Thirty wind turbine models were tested under the same conditions in an Azrieli 30 × 30 × 90 cm low-speed wind tunnel at 107,000 Reynolds number. The different types of models were obtained by parametric variations of five basic models, maintaining the same aspect ratio but varying the number of bucket phases, the orientation angles, and the gaps between the vanes. The best performing turbine model was made of one phase with two vanes of non-symmetric bipolynomial profiles that exhibited 0.2 power coefficient, relative to 0.16 and 0.13 that were obtained for symmetrical polynomial and the original Savonius type turbines, respectively. Free rotation, static forces and moments, and dynamic moments and power were measured for the sake of comparison and explanation for the variations in performances of different types of turbines. CFD calculations were used to understand the forces and moment behaviors of the optimized turbine.

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