BEM Theory Research Articles

Implementation of a New Actuator Disk Model based on BEM Theory in SU2 CFD SOFTWARE

Implementation of a New Actuator Disk Model based on BEM Theory in SU2 CFD SOFTWARE

Implementation of a new actuator disc model based on BEM theory in SU2 CFD software

Implementation of a new actuator disc model based on BEM theory in SU2 CFD software

Representation of Masculinity and Femininity Values on “Kucumbu Tubuh Indahku” by Garin Nugroho 2019

AbstractMasculinity and femininity are synonymous with stereotypes created by society and culture in general. The values contained in masculine and feminine can be seen with an open and conceptual mind. This study aims to determine the classification of masculinity and femininity and the representation of values displayed in Juno's masculinity and femininity according to Bem's perspective.This study uses a qualitative research type with the theory of BSRI (Bem Sex Role Inventory) as an indicator of data collection and the theory of semiotics of Charles Sanders Pierce as a method of data analysis. And, using the opinion of Sachiko Murata as a supporting theory. The data collection technique used is documentation by analyzing text, audio and visuals.mThe results of the study found that there are 15 masculinity personalities of Juno's character from 20 personalities according to Bem's theory, and 17 feminity personalities from 20 personalities according to Bem's theory. Classification of masculine and feminine according to Bem's theory, traditionally, Juno is considered a feminine man, so that the representation of Juno's masculinity and femininity values has a negatif self-adjustment. And non-traditionally, Juno is considered a masculine and feminine man, so that the representation of Juno's masculinity and femininity values has positive and negatif adjustments.Keywords: Masculine, Feminine, Values.

A BEM theory adaption for inclusion of hub ratio effects in HAWT rotor design and analysis

A large hub ratio in a horizontal axis wind turbine (HAWT) rotor can provide aerodynamic and structural design benefits, but the flow effects are not accounted for in the classical Blade Element Momentum Method (BEMM). Research into the effect of HAWT rotor hub ratio, necessitated development of an adaption to the BEMM, so that rotors with large hub ratios, could be designed to be aerodynamically efficient, and so that the flow effects could be included in performance prediction. Results from the BEMM with large-hub adaption were compared with results from using the classical BEMM and with results from CFD simulation. Two sets of rotors were analysed, one set in a viscous flow regime and the other in a turbulent flow regime. The BEMM with large-hub adaption, was found to provide rotor designs with better performance and provided a more accurate prediction of relative rotor power than the classical BEMM.

Aerodynamic Performance Investigation of a Small Horizontal Axis Wind Turbine with Multi-Airfoil Blade Profiles of SD2030 and E231 Using Wind Tunnel Experiments and BEM Theory Method

The goal of this study is to investigate the performance of a small horizontal axis wind turbine blade at wind speeds of lower than 5 m/sec numerically and experimentally. The rotor blade has a diameter of 0.7m and consists of two airfoils profile: the thin airfoil SD2030 selected at the outboard region, and the thick airfoil E231 at the inboard region. The former airfoil, SD2030, is highly recognized for aerodynamic performance as it is suitable for low Reynolds number (Re), while the latter airfoil E231 is likewise appropriate for low Re flow but has a higher thickness-to-chord ratio which acts as structural support and good strength at the hub. The selected airfoils were analyzed using QBlade software based on XFOIL and Blade Element Theory (BEM) for different Reynolds number. Using a low-speed wind tunnel and Reynolds number ranging from 1x105 to 5x105, experiments at pitch angles of 5ο were conducted to determine the variation in torque and predict blade performance. The results reveal that the turbine with two hybrid different airfoil profiles have achieved a better start-up response at low wind speed of 1.5 m/s and a high-power coefficient of 0.34 with 3.7 tip speed ratio. The turbine can be used to generate a power of 0.5W at 1.5 m/s and a maximum power harvest of up to 20W at a wind speed of 7m/sec. The turbine's performance compared to other small wind turbines from the literatures demonstrate good performance and the results obtained from wind tunnel data were found in satisfactory agreement with the results provided by the BEM code.

NACA2412 airfoil based method for design and aerodynamic analysis of small HAWT using modified BEM approach

Efficient utilization of wind energy depends on careful selection and suitable design of Wind Turbine (WT) blades. Small scale Wind Turbines (SWT) normally operate in the low range of Angle of Attack (AoA). This makes the task even more difficult for designing and optimization of WT blades. This article deals with an airfoil based computational approach to design the blade for a standalone small scale Horizontal Axis Wind Turbine (HAWT). A procedure has been proposed to find the important parameters and analyze the performance characteristics for a three bladed HAWT operating under the wake rotation. Computational code has been written to find optimum blade profile. Twist angle variation, chord length and other related parameters are determined with the help of program. Comparison between different types of airfoil has been made to figure out the most suitable one. Airfoil selection and design approach are intended to make Wind Turbine blade efficient specially under low range of AoA. Characteristics of the Wind Turbine obtained analytically from this procedure are compared with several other reported earlier in some of the literatures. The result obtained by the proposed procedure is simpler and more efficient than BEM theory – a method normally employed for blade design.

New Actuator Disk Model for the Analysis of Wind Turbines Wake Interaction with the Ground

Wake models based on Actuator Disk theory are usually applied to optimize the wind farm layouts and improve their overall efficiency and expected AEP. Despite the effectiveness of the existing models, most Actuator Disk approaches are based on the flow axisymmetric assumption, without considering the ground effect on the wake behavior. However, it has been shown that the mast’s height, or distance from the wind turbine to the ground, has an influence on the wake expansion on both hub’s side and at downstream of the wind turbine. Therefore, in this study, a hybrid CFD-BEM-Actuator Disk approach is developed to address the lack of the existing models. In the proposed model, the 3D wind rotor is modeled by a set of blade elements. Then, the local lift and drag forces acting on each blade element are calculated using BEM theory and incorporated into the momentum equation. This BEM-AD model is implemented in a User Defined Function (UDF) that is loaded into the CFD software. Thereby, ground effects are considered to be a wall boundary and defining a wind boundary layer profile at the inlet boundary, which describes the Atmospheric Boundary Layer (ABL). For the validation of this new Actuator Disk model, an enhanced experimental study is conducted at the Dynfluid Laboratory wind tunnel (ENSAM School Paris Tech). The Particle Image Velocimetry (PIV) measurements are used for the experimental wake explorations applied to a miniature two-bladed wind turbine. The wake developments are analyzed at two different hub heights ratio, h/D = 0.7 and 1.0 (where h is the hub height, and D is the wind rotor diameter). The analysis of the outcomes showed that the numerical simulations are in good correlation with the experimental measurements of the ENSAM wind tunnel. The numerical results show that for h/D=0.7, the upper half of the rotor operates within the boundary layer whereas the lower tip vortices are mainly developed in the horizontal direction with lower intensity compared to the upper tip vortices. This effect was not observed for the case h/D=1.0 where the rotor operates outside of the boundary layer; however, the wake centerline is upward deflected at about 0.3D. The main conclusion is that a distance above 7D must be observed between wind turbines to optimize the wind farm performance and over 1D hub height be required to limit the influence of the ground boundary layer effect.

To be assertive or not to be assertive: That is the question! Students' reactions to sexual harassment in academia.

IntroductionIn the literature, no integrated definition of sexual harassment (SH) occurs but there is clear unanimity about SH being offensive, humiliating, and intimidating behavior. Within academic settings, SH has severe negative effects on students' physical or emotional wellbeing as well as on their ability to succeed academically.MethodsThe aim of this study was to investigate the relationship between sex, gender roles, and the ways to manage SH (assertive and nonassertive reactions) in university students. It was hypothesized that female students would report more nonassertive reactions compared to male students. In addition, following the Bem theory on gender roles and using the self-report tool by the same author, it is hypothesized that female and male students, who are classified as feminine, will report more nonassertive responses, whereas male and female students, who are classified as masculine, will report more assertive responses. Our hypothesis was tested with a sample of 1,415 university students (593 men, 41.9%, and 822 women, 58.1%) who completed a questionnaire approved by the local ethical review board for research from the end of January 2019 to the first half of February 2019.ResultsContrary to our hypothesis, results showed that women react more than men in both assertive and nonassertive modalities. In addition, our results confirmed the main effect of both sex and gender roles on students' assertive and nonassertive reactions to SH in academia.ConclusionEducational programs about SH may prove useful in preventing its occurrence. Gender equality plans in academia can improve a nonsexist and safe environment for students. It is urgent to improve transparency and accountability of policies on the management of SH: academic institutions need to formulate a procedure to facilitate SH reporting, considering the sensitive balance of confidentiality and transparency issues. Support for the victims (social services, healthcare, legal representation, and advice concerning career/professional development) must be included.

Performance evaluation of an airfoil under ice accretion using CFD simulations

The profiles used in wind turbine blades have a great effect on aerodynamic behavior. The incorporation in engineering methods of the three-dimensional and rotation effects obtained through numerical simulations has allowed to substantially improve the design of the blades. A further advance in the improvement of the models is the modification of the surface state of the profile due to environmental effects. The presence of erosion, dirt, or snow on the leading edge reduces the aerodynamic behavior of the profiles. Therefore, incorporating its effects would improve predictions. However, the implementation of these effects in numerical models is complex. In this work, only the effect of the ice/snow accretion will be taken into account. The study is made using the NREL PHASE VI experimental horizontal-axis turbine with the S809 profile. The BEM theory is applied to conduct accurate 2D numerical simulations firstly, of a clean profile (unmodified) and afterwards of accreted profile. The latter is constructed by the modification of the profile in advance, following indications of the Icing ANSYS Fluent tool. Simulations are conducted under a RANS numerical approach through an SST k-ω model, which properly predicts boundary layer behavior. CFD results are evaluated at different sections of the profile and compared against predictions from other authors in terms of aerodynamic coefficients. The simulations consistently predict an increase in the drag coefficient (CD +33%), and a decrease in the lift coefficient (CL -9%). The presence of ice accretion affects the airfoil performance along the whole blade span, being slightly more pronounced towards the root of the blade. This work presents a new engineering methodology able to accurately predict airfoil performance under ice accretion at a reduced computational cost.

Review of Study on the Coupled Dynamic Performance of Floating Offshore Wind Turbines

Floating offshore wind turbines (FOWT) have attracted more and more attention in recent years. However, environmental loads on FOWTs have higher complexity than those on the traditional onshore or fixed-bottom offshore wind turbines. In addition to aerodynamic loads on turbine blades, hydrodynamic loads also act on the support platform. A review on the aerodynamic analysis of blades, hydrodynamic simulation of the supporting platform, and coupled aero- and hydro-dynamic study on FOWTs, is presented in this paper. At present, the primary coupling method is based on the combination of BEM theory and potential flow theory, which can simulate the performance of the FOWT system under normal operating conditions but has certain limitations in solving the complex problem of coupled FOWTs. The more accurate and reliable CFD method used in the research of coupling problems is still in its infancy. In the future, multidisciplinary theories should be used sufficiently to research the coupled dynamics of hydrodynamics and aerodynamics from a global perspective, which is significant for the design and large-scale utilization of FOWT.

A blade element momentum model for dual-rotor wind turbines considering inter-rotor velocity interferences

A blade element momentum model for predicting the aerodynamic performance of dual-rotor wind turbines (DRWTs) as an aerodynamic design tool is introduced in this paper. The model considers the inter-rotor axial velocity reduction and the tangential velocity components in the front rotor’s wake to model the inter-rotor velocity interferences for the inflow velocity as the input of the BEM theory. A DRWT with two NREL 5MW rotors is studied using the present model and CFD simulations. Results from the two methods show good agreements with each other in the trends of power, thrust, and aerodynamic loads on the blades despite the error in near-tip regions. The present DRWT configurations have lower optimum tip speed ratios and a wider range of high-CP speeds. The maximum efficiency of the present turbine is improved by only 5%, indicating that a dedicated blade design for DRWT aerodynamics is required to enhance power output and lower the aerodynamic loads.

Tidal current turbine blade optimisation with improved blade element momentum theory and a non-dominated sorting genetic algorithm

Tidal current energy has the advantage of predictability over most of the other renewable energy resources. However, due to the harsh operating environment and complicated site conditions, developments in this domain have been gradual. Paramount to these points is device design and optimisation of hydrodynamic performance. Recent developments in the correction models of BEM theory have further improved the accuracy of the prediction model. Using an improved blade element momentum theory model that is capable of accurately capturing the downwash angle and combining it with a well-developed and reliable non-dominated sorting genetic algorithm model, an effective and efficient tidal current turbine blade optimisation tool has been developed and is presented in this paper. This novel work incorporated a NACA generator that is capable of reproducing any NACA profile, such a tool allows the solver to analyse each and every profile used in each spanwise blade element. As a result, the model is very effective at producing tidal current turbine blades that have been optimised not only for local twist angle and chord length, but also for the suitable NACA profiles to be used at a particular spanwise blade element. The use of the non-dominated sorting genetic algorithm in this work allows the model to efficiently explore a wide range of solutions, outputting a number of tidal current turbine blades suitable for a specified operating condition. The accuracy of the performance prediction of the improved BEM model is validated against an experimentally validated tidal current turbine blade. The coefficient of determination (R2) values for power and thrust coefficient are 0.99828 and 0.99488 respectively when comparing this work with experimental measurements found in the literature. Furthermore this proves that the improved BEM model is capable of efficiently predicting hydrodynamic performance of a tidal current turbine blade to a high degree of accuracy. Further work includes implementing computational fluid dynamics for further validation and evaluation.

FEMININITY PORTRAYED IN DANTE CHARACTER IN ARISTOTLE AND DANTE DISCOVER THE SECRET OF UNIVERSE NOVEL

The purposes of this research were to find the femininity characteristics and identity developments as a homosexual in the character of Dante of Aristotle and Dante Discover the Secret of Universe novel. This research was categorized as descriptive qualitative research and was using content analysis approach. The researcher used Aristotle and Dante Discover the Secret of Universe novel as the source of data. The data were taken from the dialogues between characters and narrations that indicating Dante’s femininity characteristics based on Bem theory and his identity development as a homosexual based on Cass theory. From the finding of this research, it reveals that the character of Dante possess 16 out of 20 femininity characteristics which are affectionate, cheerful, childlike, compassionate, eager to soothe hurt feelings, feminine, gentle, gullible, sensitive of the needs of others, loyal, soft spoken, sympathetic, tender, understanding, warm, and yielding. Dante also fulfills 4 out of 6 identity developments which are identity of confusion, comparison, tolerance and acceptance. The character of Dante has femininity characteristics and he experiences the identity development phases to be a homosexual.

Experimental investigations and aerodynamic shape optimization of small horizontal-axis wind turbine blades

This study aims to optimize and investigate small horizontal-axis wind turbine blades at low wind speeds. The objective of this study is to explain the design method based on BEM theory for 0.2 m blade rotors with constant, variable, and linear chord with twisted blade geometry. MATLAB and Xfoil programs were used to apply BEM principles on wind turbines with SG6043 airfoil. Numerical and experimental studies were carried out to examine the impact of rotor solidity values from 0.057 to 0.207 and the number of blades from 3 to 7. The experimental blades were developed using a 3D printing additive manufacturing technique. The rotors were investigated in an open wind tunnel at wind speeds ranging from 2 to 8 m/s. The initial investigation range included tip speed ratios from 2 to 8 and angles of attacks from 2° to 20°. Subsequently, these parameters were varied in Matlab and Xfoil software to optimization and investigate the power coefficient, blade geometry, number of blades, and blade pitch angle. It was found that a rotor solidity of 0.055–0.085 displayed better performance.

A novel computational approach for design and performance investigation of small wind turbine blade with extended BEM theory

Blade is an important part in wind turbine system because of its vital role in extraction of energy from wind. In order to extract maximum possible energy, blade should be judiciously designed, for which it is supposed to be divided into several smaller sections (airfoil). SG6043 is selected for this work on account of its few merits over others existing airfoils. The article throws light on basis of blade element momentum theory and adopts its extended form to overcome its limitation in blade design and performance prediction while taking effect of wake into the account. This work investigates the performance of horizontal axis wind turbine (HAWT) in general, with emphasis on small HAWT over wide range of tip-speed ratio considering several effect on wind turbine. Results are validated with other experimental results published in various past literatures.

Design and optimization of a small horizontal axis wind turbine using BEM theory and tip loss corrections

In this paper, an optimization approach of a small horizontal axis wind turbine based on BEM theory including De Vries and Shen et al. tip loss corrections is proposed. The optimal blade geometry was obtained by maximizing the power coefficient along the blade using the optimal angle of attack and the optimal tip speed ratio. The Newton’s iterative method applied to axial induction factor was used to solve the problem. This study was conducted for a NACA4418 small wind turbine, at low wind velocity. Among the two used tip loss corrections, the De Vries correction was found to be the most suitable for this blade optimization method. The optimal design was obtained for a tip speed ratio of 5 and has recorded a power coefficient equal to 0.463.

Development of a wind turbine simulator to design and test micro HAWTs

The development of a micro wind turbine simulator is presented in the current study. The simulator is employed to test and assess the design and the performance of micro horizontal axis wind turbines (HAWT). These turbines can be used as micro wind turbines being utilized for household applications. The main system consists of a wind simulator, models of rotor blades, a tower model with a nacelle at the top. In this study, nacelle comprises a low-power step motor directly coupled with the turbine’s axis at its input and a designed circuit at its output to measure the generated power. As an innovative part of the simulator, the fan of the simulator is mounted within a guiding slide which can enable the user to change the yaw angle while maintaining the same distance from the HAWT. To calibrate the simulator, the results obtained from experimental investigations (i.e. wind simulator) were compared with BEM theory, CFD simulation as well as wind tunnel measurements. In addition, different conditions including yawed rotor and rotors with blades extending from the uniform inflow of the fan are experimentally assessed. Overall, the results show satisfactory response of the system in reproducing the characteristics of a given micro turbine at various conditions particularly when the tip speed ratio is close to the design value.

On the upscaling approach to wind tunnel experiments of horizontal axis hydrokinetic turbines

In this work, we proposed an upscaling methodology to extrapolate results from wind tunnel experiments with small-scale model to the full-size hydrokinetic turbine. Small-scale 1:20 wind tunnel experiments ( $${\hbox {Re}}\sim 10^4$$ ), with a three-blade horizontal axis turbine, were carried out looking to identify the characteristic curves of a full-size turbine operating in water ( $${\hbox {Re}}\sim 10^6$$ ). The lack of dynamic similarity due to unmatched Reynolds numbers is analyzed in the framework of blade element momentum theory arguments. A new semi-empirical power-law equation is achieved, uniquely based on the BEM theory which relates the power coefficients of model and full-size turbine to the Reynolds numbers and a power factor, specific to each turbine. Computational fluid dynamic CFD simulations for the same rotor geometry, simulating different runners with varying diameters from small-scale model to full-scale turbine are carried out to validate the upscaling arguments, and to verify the accuracy of the power coefficient curves predicted by proposed methodology.

Geometrical Design of a Rotor Blade for a Small Scale Horizontal Axis Wind Turbine

In the present study, Blade Element Momentum theory (BEMT) has been implemented to heuristically design a rotor blade for a 2kW Fixed Pitch Fixed Speed (FPFS) Small Scale Horizontal Axis Wind Turbine (SSHAWT). Critical geometrical properties viz. Sectional Chord ci and Twist distribution θTi for the idealized, optimized and linearized blades are analytically determined for various operating conditions. Results obtained from BEM theory demonstrate that the average sectional chord ci and twist distribution θTi of the idealized blade are 20.42% and 14.08% more in comparison with optimized blade. Additionally, the employment of linearization technique further reduced the sectional chord ci and twist distribution θTi of the idealized blade by 17.9% and 14% respectively, thus achieving a viable blade bounded by the limits of economic and manufacturing constraints. Finally, the study also reveals that the iteratively reducing blade geometry has an influential effect on the solidity of the blade that in turn affects the performance of the wind turbine.

Hydraulically actuated horizontal axis wind turbine pitch control by model free adaptive controller

In the present work a model free fuzzy feedforward PID controller has been developed for pitch control application of the horizontal axis wind turbine through electrohydraulic pitch actuation system. The controller has been designed to achieve maximum power tracking and protect from high wind gusts even with fault in the actuating system. Electrohydraulic pitch actuating system has high power to weigh ratio, self-lubricating property, good controllability etc. as its merit of application. Nonlinear mathematical model of small horizontal axis wind turbine along with proportional valve controlled electrohydraulic pitch actuating system has been developed. The BEM theory has been used to estimate aerodynamic load on the turbine blade and pitch for maximum power capture by the turbine with the variation of the wind speed. The present model has been validated with experimental results. The performance of the proposed fuzzy feedforward PID controller has been investigated with various test signals as well as predicted pitch demand from wind data for maximum power tracking and to save from high wind gusts. The performance index of proposed fuzzy feedforward PID controller has been found as 0.08606, 0.08849 and 0.09809 with normal leakage, high leakage and very high leakage respectively.