2D and 2.5D Numerical Simulations for Vortex-Induced Vibration (VIV) of a 1.5:1 Rectangular Cylinder

2021 ◽  
Author(s):  
Bowen Yan ◽  
Yangjin Yuan ◽  
Dalong Li ◽  
Ke Li ◽  
Qingshan Yang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Numerical Simulations ◽  
Phase Difference ◽  
Vortex Shedding ◽  
Lift Force ◽  
Small Scale ◽  
Aerodynamic Damping ◽  
Displacement Response ◽  
Wind Speeds ◽  
Rectangular Cylinder

The semi-periodic vortex-shedding phenomenon caused by flow separation at the windward corners of a rectangular cylinder would result in significant vortex-induced vibrations (VIVs). Based on the aeroelastic experiment of a rectangular cylinder with side ratio of 1.5:1, 2-dimensional (2D) and 2.5-dimensional (2.5D) numerical simulations of the VIV of a rectangular cylinder were comprehensively validated. The mechanism of VIV of the rectangular cylinder was in detail discussed in terms of vortex-induced forces, aeroelastic response, work analysis, aerodynamic damping ratio and flow visualization. The outcomes showed that the numerical results of aeroelastic displacement in the cross-wind direction and the vortex-shedding procedure around the rectangular cylinder were in general consistence with the experimental results by 2.5D numerical simulation. In both simulations, the phase difference between the lift and displacement response increased with the reduced wind speed and the vortex-induced resonance (VIR) disappeared at the phase difference of approximately 180∘. The work done by lift force shows a close relationship with vibration amplitudes at different reduced wind speeds. In 2.5D simulations, the lift force of the rectangular cylinder under different wind speeds would be affected by the presence of small-scale vortices in the turbulence flow field. Similarly, the phase difference between lift force and displacement response was not a constant with the same upstream wind speed. Aerodynamic damping identified from the VIV was mainly dependent on the reduced wind speed and negative damping ratios were revealed at the lock-in regime, which also greatly influenced the probability density function (PDF) of wind-induced displacement.

scholarly journals Wind Power potential in Kigali and Western provinces of Rwanda

2015 ◽  
Vol 2 (1) ◽  
pp. 25-36
Author(s):  
Otieno Fredrick Onyango ◽  
Sibomana Gaston ◽  
Elie Kabende ◽  
Felix Nkunda ◽  
Jared Hera Ndeda
Keyword(s):  
Wind Speed ◽  
Probability Density ◽  
Wind Power ◽  
Wind Direction ◽  
Small Scale ◽  
Energy Potential ◽  
Wind Speeds ◽  
Mean Wind Speed ◽  
Wind Energy Potential ◽  
Low Wind Speeds

Wind speed and wind direction are the most important characteristics for assessing wind energy potential of a location using suitable probability density functions. In this investigation, a hybrid-Weibull probability density function was used to analyze data from Kigali, Gisenyi, and Kamembe stations. Kigali is located in the Eastern side of Rwanda while Gisenyi and Kamembe are to the West. On-site hourly wind speed and wind direction data for the year 2007 were analyzed using Matlab programmes. The annual mean wind speed for Kigali, Gisenyi, and Kamembe sites were determined as 2.36m/s, 2.95m/s and 2.97m/s respectively, while corresponding dominant wind directions for the stations were ,  and  respectively. The annual wind power density of Kigali was found to be  while the power densities for Gisenyi and Kamembe were determined as and . It is clear, the investigated regions are dominated by low wind speeds thus are suitable for small-scale wind power generation especially at Kamembe site.

Direct Numerical Simulations of Horizontally Oblique Flows Past Three-Dimensional Circular Cylinder Near a Plane Boundary

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Chunning Ji ◽  
Zhimeng Zhang ◽  
Dong Xu ◽  
Narakorn Srinil
Keyword(s):  
Circular Cylinder ◽  
Numerical Simulations ◽  
Vortex Shedding ◽  
Lift Force ◽  
Three Dimensional ◽  
Direct Numerical Simulations ◽  
Plane Boundary ◽  
Hydrodynamic Drag ◽  
Vibration Prediction ◽  
Inclination Angles

Abstract Understanding hydrodynamics of a free-spanning pipeline subjected to omni-directional flows is important to engineering design. In this study, horizontally oblique flows past a three-dimensional circular cylinder in the vicinity of a plane boundary are numerically investigated using direct numerical simulations. Parametric studies are carried out at the normal Reynolds number of 500, a fixed gap-to-diameter ratio of 0.8 and five flow inclination angles (α) ranging from 0 deg to 60 deg with an increment of 15 deg. Two distinct vortex-shedding modes are observed: parallel (α ≤ 15 deg) and oblique (α ≥ 30 deg) vortex shedding. The wake evolution is further divided into two or three stages depending on α. The occurrence of the oblique vortex shedding is accompanied by the base pressure gradient along the cylinder span and the resultant axial flows near the cylinder base. The total hydrodynamic drag and lift force coefficients decrease from being the parallel mode to the oblique mode, owing to the intensified three-dimensionality of wake flows and the phase differences in the spanwise vortex shedding. The independence principle (IP) is found to be valid in predicting hydrodynamic forces and wake patterns when α ≤ 15 deg. This IP might produce unacceptable errors when α > 15 deg. In comparison with the mean drag force, the fluctuating lift force is more sensitive to the inclination angle. The IP validity range is substantially smaller than that in the case of flow past a wall-free cylinder. Such finding would be practically useful for vortex-induced vibration prediction.

scholarly journals An Evaluation of Hurricane Superintensity in Axisymmetric Numerical Models

2019 ◽  
Vol 76 (6) ◽  
pp. 1697-1708 ◽  
Author(s):  
Raphaël Rousseau-Rizzi ◽  
Kerry Emanuel
Keyword(s):  
Wind Speed ◽  
Numerical Simulations ◽  
Turbulent Mixing ◽  
Numerical Models ◽  
Surface Wind ◽  
Inviscid Limit ◽  
Carnot Cycle ◽  
Wind Speeds ◽  
Gradient Wind ◽  
Hurricane Wind

Abstract Potential intensity (PI) is an analytical bound on steady, inviscid, axisymmetric hurricane wind speed. Studies have shown that simulated hurricane azimuthal wind speed can greatly exceed a PI bound on the maximum gradient wind. This disparity is called superintensity (SI) and has been attributed to the contribution of the unbalanced flow to the azimuthal wind. The goals of this study are 1) to introduce a new surface wind PI (PIs), based on a differential Carnot cycle and bounding the magnitude of the surface winds; 2) to evaluate SI in numerical simulations with respect to diagnostic PI bounds on gradient wind (PIg), azimuthal wind (PIa), and surface wind (PIs); and 3) to evaluate the validity of each PI bound based on the SI computations. Here, we define superintensity as the normalized amount by which each version of PI is exceeded by the quantity it bounds. Axisymmetric tropical cyclone simulations are performed while varying the parameterized turbulent mixing as a way of estimating SI in the inviscid limit. As the mixing length decreases, all three bounded wind speeds increase similarly from a sub-PI state to a marginally superintense state. This shows that all three forms of PI evaluated here are good approximations to their respective metrics in numerical simulations.

Optimization of the Wind Turbine Designs for Areas With Low Wind Speeds

2015 ◽  
Author(s):  
Mohammed S. Mayeed ◽  
Adeel Khalid
Keyword(s):  
Energy Consumption ◽  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Small Scale ◽  
Wind Speeds ◽  
Low Wind Speed ◽  
Average Wind ◽  
The World

Wind energy has been identified as an important source of renewable energy. In this study, several wind turbine designs have been analyzed and optimized designs have been proposed for low wind speed areas around the world mainly for domestic energy consumption. The wind speed range of 4–12 mph is considered, which is selected based on the average wind speeds in the Atlanta, GA and surrounding areas. These areas have relatively low average wind speeds compared to various other parts of the United States. Traditionally wind energy utilization is limited to areas with higher wind speeds. In reality a lot of areas in the world have low average wind speeds and demand high energy consumption. In most cases, wind turbines are installed in remote offshore or away from habitat high wind locations, causing heavy investment in installation and maintenance, and loss of energy transfer over long distance. A few more advantages of small scale wind turbines include reduced visibility, less noise and reduced detrimental environmental effects such as killing of birds, when compared to traditional large turbines. With the latest development in wind turbine technology it is now possible to employ small scale wind turbines that have much smaller foot print and can generate enough energy for small businesses or residential applications. The low speed wind turbines are typically located near residential areas, and are much smaller in sizes compared to the large out of habitat wind turbines. In this study, several designs of vertical and horizontal axes wind turbines are modeled using SolidWorks e.g. no-airfoil theme, airfoil blade, Savonius rotor etc. Virtual aerodynamic analysis is performed using SolidWorks Flow simulation software, and then optimization of the designs is performed based on maximizing the starting rotational torque and ultimate power generation capacity. From flow simulations, forces on the wind turbine blades and structures are calculated, and used in subsequent stress analysis to confirm structural integrity. Critical insight into low wind speed turbines is obtained using various configurations, and optimized designs have been proposed. The study will help in the practical and effective utilization of wind energy for the areas around the globe having low average wind speeds.

Methods for Improving Lift Force of Wind Turbine Aerofoil Blades during Low Wind Speed Conditions – A Review

2015 ◽  
Vol 787 ◽  
pp. 134-137
Author(s):  
S.P.R. Febi Ponwin ◽  
S. Rajkumar
Keyword(s):  
Reynolds Number ◽  
Renewable Energy ◽  
Wind Speed ◽  
Laminar Flow ◽  
Wind Turbine ◽  
Lift Force ◽  
Renewable Energy Sources ◽  
Small Scale ◽  
Good Efficiency ◽  
Low Wind Speed

Wind energy is one of the promising renewable energy resources. The challenges in utilizing the renewable energy sources are making them reliable with good efficiency. Wind turbine plays a major role in industrial power supply during heavy wind conditions. However, in domestic applications, the small scale wind turbine has major issue of low starting torque due to low wind speed near the ground surface. These conditions make the air motion as laminar flow with the Reynolds number less than 5x105. Hence, in some adverse condition there is a laminar flow separation which increases the drag and consequently reduces the lift force. This paper gives a comprehensive review on the investigations that are being carried out on low Reynolds number regime aerofoil and laminar separation bubble to enhance the lift force especially at low wind speed conditions.

Designing Wind Turbines for Areas With Low Wind Speeds

2014 ◽  
Author(s):  
Mohammed S. Mayeed ◽  
Adeel Khalid
Keyword(s):  
Energy Consumption ◽  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbines ◽  
Small Scale ◽  
Wind Speeds ◽  
Low Wind Speed ◽  
Average Wind ◽  
The World ◽  
Low Wind Speeds

Today’s wind turbines are designed in a wide range of vertical and horizontal axis types. In this study, several wind turbines are designed for low wind speed areas around the world mainly for domestic energy consumption. The wind speed range of 4–12 mph is considered, which is selected based on the average wind speeds in the Atlanta, GA and surrounding areas. These areas have relatively low average wind speeds compared to various other parts of the United States. Wind energy has been identified as an important source of renewable energy. Traditionally wind energy utilization is limited to areas with higher wind speeds. In reality a lot of areas in the world including Atlanta, GA., have low average wind speeds and demand high energy consumption. In most cases, wind turbines are installed in remote offshore or away from habitat locations, causing heavy investment in installation and maintenance, and loss of energy transfer over long distances. Therefore, the main focus of this study is to extract wind energy domestically at low wind speeds. A few more advantages of small scale wind turbines include reduced visibility, less noise and reduced detrimental environmental effects such as killing of birds, when compared to traditional large turbines. With the latest development in wind turbine technology it is now possible to employ small scale wind turbines that have much smaller foot print and can generate enough energy for small businesses or residential applications. The low speed wind turbines are typically located near residential areas, and are much smaller in sizes compared to the large out of habitat wind turbines. In this study, several designs of wind turbines are modeled using SolidWorks. Virtual aerodynamic analysis is performed using SolidWorks Flow simulation software, and then optimization of the designs is performed based on maximizing the starting rotational torque and acceleration. From flow simulations, forces on the wind turbine blades and structures are calculated, and used in subsequent stress analysis to confirm structural integrity. Critical insight into the low wind speed turbine design is obtained using various configurations and the results are discussed. The study will help identify bottlenecks in the practical and effective utilization of low speed wind energy, and help devise possible remedial plans for the areas around the globe that get low average wind speeds.

scholarly journals Investigation on the Performance of a Portable Power Generation System with a Low-Cost Vertical Axis Wind Turbine

2021 ◽  
Vol 11 (6) ◽  
pp. 7809-7813
Author(s):  
M. F. Basar ◽  
A. M. Norazizi ◽  
I. Mustaffa ◽  
C. T. Colin ◽  
S. N. S. Mirin ◽  
...  
Keyword(s):  
Power Generation ◽  
Wind Speed ◽  
Wind Turbine ◽  
Low Cost ◽  
Public Awareness ◽  
Vertical Axis ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Wind Speeds ◽  
Portable Power

The purpose of this project was to develop an innovative, small-scale, and portable vertical axis wind turbine for power generation. The wind turbine was simple in design and economical. Wind speeds ranging from 2.0ms-1 to 7.0ms-1 were tested on the proposed wind turbine. The experiments revealed that the turbine required a minimum wind speed of 3.9ms-1 to operate. According to the results, the proposed turbine achieved its maximum power output of 5.6W at a rotational speed of 65rpm when the wind speed was 7.0m/s. Additionally, voltage and current increased proportionately with increasing wind speed. The proposed system showed an average coefficient factor between 0.10 and 0.12. This portable wind turbine potentially revolutionizes industry while raising public awareness about clean and renewable energy.

scholarly journals DESIGN OF VERTICAL AXIS SAVONIUS WINDMILL FOR GENERATING ELECTRICITY USING PERMANENT MAGNET

Tibuana ◽  
2020 ◽  
Vol 3 (01) ◽  
pp. 61-66
Author(s):  
Sagita Rochman
Keyword(s):  
Wind Speed ◽  
Permanent Magnet ◽  
Large Scale ◽  
Electrical Energy ◽  
Vertical Axis ◽  
Small Scale ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Low Wind Speed ◽  
Wind Potential

At present the use of wind energy in Indonesia is still relatively low, but has enormous potential. One reason is because the average wind speed in the territory of Indonesia is classified as low wind speed, which ranges from 3 m / s to 5 m / s making it difficult to produce electrical energy on a large scale. However, the wind potential in Indonesia is available almost all year long, making it possible to develop small-scale power generation systems. Innovations in modifying windmills need to be developed so that in conditions of low wind speeds can produce electrical energy. In this research, a prototype was developed by designing a vertical axis windmill power plant model Savonius using a permanent magnet generator, which can produce optimal electrical energy by utilizing relatively low wind speeds.From the generator test it was found that with a rotor rotation of 50 rpm up to 500 rpm can produce an electrical voltage of 0.02V to 10V and an electric current of 0.60A to 4.53A.

scholarly journals Second Wind: Extending the official wind gust records with citizen science observations

2021 ◽  
Author(s):  
Kirien Whan ◽  
Kate Saunders
Keyword(s):  
Quality Control ◽  
Wind Speed ◽  
Citizen Science ◽  
Small Scale ◽  
Wind Gust ◽  
High Quality ◽  
Data Set ◽  
Wind Speeds ◽  
Wind Gusts ◽  
Extreme Wind

<p>Extreme wind gusts have severe socio-economic impacts, so any source of extra information on this variable is invaluable for mitigating associated damages and<br />protecting vulnerable communities. Unfortunately, networks of ocial measurement stations are limited in their ability to observe wind gusts. Official stations<br />are separated by vast distances, so extreme wind gusts often go unobserved due to the highly localised nature of these events. A wealth of additional observa-<br />tions is available from personal weather stations (PWSs) and could be used in combination with official observations to observe extreme gust events. However,<br />concerns about underlying data quality have to date prevented the usage of gust data from PWSs.</p> <p>Research for other meteorological variables has demonstrated that with appropriate quality control PWSs can contribute high-quality observations that complement ocial measurements. It is well known that PWSs can provide useful and reliable temperature and precipitation observations. For crowd-sourced wind variables, the situation is more dicult. Crowd-sourced wind observations have di erent sources of error that pose signi cant challenges to quality control. For example, instrumentation is non-standard which results in di erent sensor sensitivities, and non-standard station placements introduce severe spatial in-consistencies and result in censoring of low wind speeds. Chen et al. (2021) recently developed a  exible approach to quality control and bias adjustment (QC/BA) that addresses this for wind speeds. They incorporate QC steps for official stations and develop new QC/BA steps to address the novel challenges posed by crowd-sourced data. Chen et al. (2021) showed after QC/BA, the wind speed climatology of a network of PWSs matched well with the climatology of ocial stations, and the wind speed variability between PWSs was similar to that of official  tations. Additionally, subsequent analysis has shown that the quality controlled and bias adjusted data from PWSs is able to detect small scale extreme wind speeds  ssociated with thunderstorms, that were not observed at official stations. No attempt has yet been made to quality control crowd-sourced observations of wind gusts  espite how impractical it is to obtain widespread observations of wind gusts using standard techniques.</p> <p>In this project we will develop the necessary methods and software for the QC/BA of wind gusts. As part of this, we will develop inter-variable consistency checks between crowd-sourced wind speeds, wind gusts and wind directions. We will also produce an open-source, high-quality wind gust data set from PWSs that can be used to improve forecasts, warnings, and veri cation of extreme gusts.</p> <p><strong>References</strong></p> <p>Chen, J., Saunders, K. & Whan, K. (2021), `Quality control and bias correction of citizen science wind observations', <em>Quarterly Journal of the Royal Meteo-</em><br /><em>rological Society (under review) </em>.</p>

scholarly journals Technical Assessment of Wind Energy Potentiality in Malaysia Using Weibull Distribution Function

2021 ◽  
Vol 86 (1) ◽  
pp. 1-13
Author(s):  
Abdul Rashid Shoib ◽  
Djamal Hissein Didane ◽  
Akmal Nizam Mohammed ◽  
Kamil Abdullah ◽  
Mas Fawzi Mohd Ali
Keyword(s):  
Distribution Function ◽  
Wind Speed ◽  
Wind Energy ◽  
Weibull Distribution ◽  
Wind Power ◽  
Maximum Energy ◽  
Small Scale ◽  
Weibull Distribution Function ◽  
Average Value ◽  
Wind Speeds

In this paper, an assessment of the wind characteristics and wind power potentials in three different stations (Chuping, Kuantan and Melaka) in Malaysia has been analyzed at 80 m height. The assessment technique was based on the two-parameter Weibull distribution function over three recent consecutive years (2018-2020) while aiming to establish the potentiality of the wind as a source of power generation in these sites. The results demonstrate that the monthly highest mean wind speeds were 4.42 m/s, 2.96 m/s and 2.17 m/s at Melaka, Kuantan and Chuping, respectively. The highest most probable wind speed was 4.70 m/s and the wind speed carrying maximum energy was 1.74 m/ both speeds occurred at Maleka in 2019. The yearly highest Weibull shape parameter was 1.69 and the scale parameter was 2.96 m/s. Among the three stations, Melaka has shown the highest wind power potentials with an average value of 26.10 W/m2 followed by Kuantan with 12.71 W/m2 and Chuping with 6.80 W/m2 wind power density. The corresponding wind energy densities were 595.58 kWh/m2/year, 111.37 kWh/m2/year and 228.65 kWh/m2/year for Chuping, Kuantan and Melaka station, respectively. The prevailing wind directions are northeast at both Kuantan and Melaka station, west and southwest direction at Chuping station. It is therefore concluded that the potentiality of the wind power of the sites covered in the present study is only feasible for small-scale power generations.

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