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1

Rotors of vertical-axial wind turbines assembled in bearings and aerodynamic characteristics of a blade with unclosed wing profile

Panda Anton, Rozhkova Lyudmila, Kuznetsov Eduard, Nahornyi Volodymyr

Management Systems in Production Engineering

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2022

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nr 4 (30)

298--303

EN

In world practice, traditional blades used in high-speed wind turbines, both horizontal-axial and vertical-axial, have a wing-shaped profile. However, for horizontal-axial wind turbines, blades with such a profile have a fairly narrow range of operating values of the angle of attack of the incoming air flow and a low value of the moment of pulling from place. As for vertical-axial wind turbines, the self-starting of the rotor with wing blades is completely absent and additional devices are needed to start the rotor into operation. In order to ensure the selfstarting of the rotor and the operation of the wind turbine at high and low wind speeds, a new shape of the blade profile was developed, called non-closed wing profile. The concept of the development is that the blade should have a configuration in which the pulling force is involved at the beginning of the movement, and then, with the establishing of the movement, a lifting force would arise, which acquires a prevailing character in the operating mode. The article presents the results of experimental studies of the aerodynamic characteristics of the developed non-closed wing blades. One of the results obtained is to determine the effect of the thickness of the blade profile on the range of values of subcritical angles of attack of the incoming air flow and the differences between the nature and range of changes in the coefficients of lifting force and pulling force in a traditional wing blade and a blade with a non-closed wing profile. Studies of the rotor model of a vertical-axial wind turbine with non-closed wing blades have confirmed the presence of its self-starting and operability even at low wind speeds.

2

Study of flow pattern on a hydrofoil with structural and profile modification

Chada Jithendra Sai Raja, Rao B. S. V. Rama

Journal of Mechanical and Energy Engineering

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2022

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Vol. 6, No 1

27--31

EN

Moving through water takes much more effort than walking through air, and this explains why ships travel much more slowly than automobiles and aircraft. Water is almost 1000 times denser than air, so most of the energy produced by a boat is taken up by dragging (water resistance). Hydrofoils travel much more quickly than ordinary boats, not by pushing through water but by raising the hull (the main body) of the boat upward so it can glide above the waves. Hydrofoil is one of the typical factors that affect the vortex structure and flow characteristics of hydraulic machinery. In order to enhance the utilisation efficiency of hydraulic machinery in marine energy, parallel grooves are proposed and applied to the hydrofoil. Following that, a numerical analysis is performed using the SST k- turbulence model, and the effects of the hydrofoil profile, the angle of attack and the flow are investigated. The profiles of NACA 0066, NACA 8412, NACA M2 and RAE 104 are considered for the study. The performance is analysed based on the lift to drag ratio. The best model from this is given with surface modification and the flow study is carried out at different angles of attack. The modified profile of NACA 8412 with parallel groves has shown the highest lift to drag ratio at a 12 degree angle of attack.

3

Numerical analysis and optimization of a winglet sweep angle and winglet tip chord for improvement of aircraft flight performance

Al-Khafaji Ali J. Dawood, Panatov Gennady S., Boldyrev Anton S.

Diagnostyka

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2022

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Vol. 23, No. 2

art. no. 2022210

EN

In this paper, a study of the effect of winglet sweep angle and winglet tip chord of the aircraft wing on the aerodynamics performances and how to improve it are carried out, assuming Cant angle 60°, winglet height = 3.5 m, Toe angle = -5°, and Twist angle = +5°. Different sweep angles tested (-25°, -15°, 0°, +15°, +25°, +35°, and +45°) and winglet tip chord (0.25, 0.375, and 0.5 m). Four Angle of attack is presented (0°, 3°, 6°, and 9°). The aerodynamics properties of the wing were measured in terms of calculated lift to drag ratio to decide which wing has a high value of lift and lower drag. All models of a wing (eighty-four models) are drawn for 3D using the SOLIDWORKS program. Boeing 737-800 wing dimensions were used. All models of a wing were analyzed using ANSYS FLUENT. The results showed that sweep angle and winglet tip chord of the winglet by changing their configuration can improve aerodynamic performance for various attack angles. The maximum value of the lift to drag ratio was obtained with a sweep angle -15°, winglet tip chord 0.375m, and angle of attack 3°.

4

Heat transfer and friction factor correlation for inclined spherical ball roughened solar air heater

Murmu Ramesh, Kumar Parmanand, Singh Hari N.

Archives of Thermodynamics

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2020

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Vol. 41, no 2

3--34

EN

Flow mechanism under roughened solar air heater is quite complex. This paper is an effort towards determining the governing equations for heat transfer and friction factor for inclined spherical balls roughened ducts. With the availability of these equations, it is easier to predict the thermal and thermohydraulic performance of such roughened solar air heaters. The governing equations are derived based on the experimental data generated under actual outdoor condition at the test rig designed and fabricated at the terrace of the Mechanical Engineering Department, the National Institute of Technology Jamshedpur in India, in terms of roughness and flow parameters. Maximum augmentation in Nusselt number and friction factor for varying relative roughness pitch, relative roughness height, spherical ball height to diameter ratio, and angle of attack was respectively found to be of the order of 2.1 to 3.54 times, 1.87 to 3.21 times, 2.89 to 3.27 times and 1.74 to 3.56 times for Nusselt number and 0.84 to 1.79 times, 1.46 to 1.91 times, 1.67 to 2.34 times and 1.21 to 2.67 times for friction factor in comparison to non-roughened duct. The optimum roughness parameters under present investigation have been found.

5

Experimental and Theoretical Study on a Wind Energy Unit

Abusamaha Hanan M., Dawoud Farah, Al-Qalab B., Ayadi O.

Journal of Ecological Engineering

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2019

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Vol. 20, nr 6

207--214

EN

The conversion process in the wind turbine, from mechanical (kinetic) energy to electrical energy, is affected by many factors that increase or decrease the useful output of the wind energy convertor. In this paper, three factors were studied experimentally on a Horizontal Axis Wind Energy Unit “EEEC” in laboratory-scale. The aim of this experiment was to study the influence of the number of blades, the angle of attack and the incident angle on the wind energy unit parameters to optimize its efficiency. For this purpose, the effect of the number of blades was studied firstly, in order to select the number of blades where the maximum inputs obtained at lab ambient temperature 25 °C and atmospheric pressure. Then, different readings of the incident angle and angle of attacks were taken. The data was analyzed using Microsoft Excel software. The results show that the maximum parameters of wind unite energy that produce the maximum efficiency, namely: voltage (volt), current (ampere) and rotational speed (rpm) are obtained when the number of blades is 4, the incident angle is 0° (when the rotor direction is with wind direction) and the angle of attack is 75°. Finally, these results were implemented in a simulation program (HOMER software) that uses this turbine in a resident along with storage to cover the needs of a selected house.

6

The effect of angle of attack on the generated wave propagation

Javanmardi M., Binns J., Izham M. I. C., Rafieshahraki J.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2017

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nr 50 (122)

36--41

EN

The presented work is an experimental investigation into the waves generated by a pressure source moving in a straight channel. Wave fields generated by the moving pressure source are described and the effects of angle of attack on the generated wave height, surfable wave quality, drag and vertical forces are presented. The main objective of this study was to investigate the relationship between the angle of attack and the generated wave height across the towing tank width and the surfable wave quality. The investigations were conducted at the Australian Maritime College towing tank on a wavedozer at four different attack angles at various speeds. Three wave probes were installed across the channel to record the generated wave heights. Based on the experimental results, it was concluded that smaller angles of attack produced higher quality surfable waves compared to larger angles of attack, while the height of the generated wave has a direct relationship with the angle of attack. By comparing the forces for different models, it was concluded that the pressure source with the lowest angle of attack has the minimum drag but maximum displacement.

7

The Effect of Angle of Attack and Flow Conditions on Turbulent Boundary Layer Noise of Small Wind Turbines

Afanasieva N.

Archives of Acoustics

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2017

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Vol. 42, No. 1

83--91

EN

The article aims to solve the problem of noise optimization of small wind turbines. The detailed analysis concentrates on accurate specification and prediction of the turbulent boundary layer noise spectrum of the blade airfoil. The angles of attack prediction for a horizontal axis wind turbine (HAWT) and the estimation based on literature data for a vertical axis one (VAWT), were conducted, and the influence on the noise spectrum was considered. The 1/3-octave sound pressure levels are obtained by semi-empirical model BPM. Resulting contour plots show a fundamental difference in the spectrum of HAWT and VAWT reflecting the two aerodynamic modes of flow that predefine the airfoil self-noise. Comparing the blade elements with a local radius of 0.875 m in the HAWT and VAWT conditions the predicted sound pressure levels are the 78.5 dB and 89.8 dB respectively. In case of the HAWT with predicted local angle of attack ranging from 2.98º to 4.63º, the acoustic spectrum will vary primarily within broadband frequency band 1.74–20 kHz. For the VAWT with the local angle of attack ranging from 4º to 20º the acoustic spectrum varies within low and broadband frequency bands 2 Hz – 20 kHz.

8

Experimental determination of aerodynamic characteristics of the plane's wing with the volume generators

Lemko O. L., Molodchyk A., Predachenko K.

Prace Instytutu Lotnictwa

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2016

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Nr 4 (245)

79--86

EN

This paper is devoted to the results of studies in a wind tunnel model aircraft mounted with the vortex generators on the wing leading edge. The article presents away to improve the aerodynamic characteristics with vortex generators on the leading edge in the direct flow. It is shown that the vortex generators increase the lift force and the critical angle of attack due to the impact of large-scale vortices on the flow separation. Experimental data of studies of the wing in the wind tunnel showed rationality of use of volume generators - there usage enlarges the range of flight angles of attack and significantly increases lift-to-drag ratio.

PL

Niniejsza praca poświęcona jest wynikom badań w tunelu aerodynamicznym modelu samolotu wyposażonemu w generatory wirów na krawędzi natarcia skrzydła. W artykule przedstawiono sposób na poprawę właściwości aerodynamicznych samolotu z generatorami wirów na krawędzi natarcia w bezpośrednim strumieniu powietrza. Wykazano, że generatory wirów prowadzą do zwiększenia siły nośnej i krytycznego kąta natarcia z powodu wpływu dużych wirów na rozdzielenie przepływu. Dane doświadczalne badania skrzydła w tunelu aerodynamicznym wykazały, racjonalność wykorzystania generatorów wirów. Wykorzystanie powiększa zakres kątów natarcia i znacznie zwiększa współczynnik siły nośnej.

9

Investigations of Strouhal numbers of iced cable models of cable-supported bridges with respect to angle of wind attack

Górski P., Tatara M., Pospišil S., Kuznetsov S., Marušić A.

Czasopismo Techniczne. Budownictwo

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2015

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Y. 112, iss. 2-B

417--432

EN

The influence of the ice accretion, angle of attack and Reynolds number on the flow field around iced cables of cablesupported bridges is not clearly understood. The Strouhal number is one of the most important parameters which is necessary for an analysis of the vortex excitation response of slender structures. This paper presents the method and results of wind tunnel investigations of the Strouhal number of stationary iced cable models of cable-supported bridges. The investigations were conducted in a climatic wind tunnel laboratory of the Czech Academy of Sciences in Telč. The methodology leading to the experimental icing of the inclined cable model in the climatic section of the laboratory was prepared. The shape of the ice on the cable was registered by photogrammetry and numerical evaluation. For the aerodynamic investigations, the iced cable model in a smaller scale was reproduced using a 3D printing procedure. The Strouhal number was determined within the range of the Reynolds number between 2.4·104 and 16.4·104, based on the dominant vortex shedding frequency measured in the flow behind the model. The model was orientated at three principal angles of wind attack for each of the Reynolds number values. In order to recognize the tunnel blockage effect, the Strouhal number of a smooth circular cylinder was tested. Strong agreement with the generally reported value in the subcritical Reynolds number range for a circular cylinder was obtained.

PL

Wpływ oblodzenia, kąta natarcia wiatru i liczby Reynoldsa na zjawisko opływu powietrza wokół oblodzonych cięgien mostów podwieszonych nie został dotychczas dobrze poznany. Liczba Strouhala jest jednym z ważniejszych parametrów, którego znajomość jest niezbędna na etapie analizy odpowiedzi smukłych konstrukcji na wzbudzenie wirowe. W artykule przedstawiono sposób i wyniki badań liczby Strouhala nieruchomych modeli oblodzonych cięgien mostów podwieszonych. Badania wykonano w tunelu aerodynamicznym z komorą klimatyczną Laboratorium Czeskiej Akademii Nauk w Telč. W komorze klimatycznej wykonano doświadczalne oblodzenie modelu cięgna o osi nachylonej pod kątem 30° do płaszczyzny poziomej. Kształt oblodzonej powierzchni zarejestrowano metodą fotogrametrii cyfrowej. Do badań w tunelu aerodynamicznym wykonano nowy model sekcyjny oblodzonego cięgna metodą druku 3D. Liczbę Strouhala wyznaczono w zakresie wartości liczby Reynoldsa od 2,4·104 do 16,4·104 na podstawie pomiaru częstości odrywania się wirów w śladzie aerodynamicznym za modelem. Badania wykonano przy trzech podstawowych kierunkach napływającego powietrza. W celu określenia wpływu zjawiska blokowania tunelu na wyniki pomiarów wykonano badanie liczby Strouhala gładkiego walca kołowego. Otrzymane wartości były zgodne z wartościami podanymi w literaturze przedmiotu w zakresie podkrytycznym liczby Reynoldsa.

10

Wykorzystanie nawigacji inercjalnej i satelitarnej do estymacji kąta natarcia

Popowski S., Dąbrowski W.

Pomiary Automatyka Robotyka

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2011

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R. 15, nr 2

774-782

PL

W referacie przedstawiono problemy związane z estymację kąta natarcia na obiektach latających. Szczegółowo zaprezentowano metody estymacji kąta natarcia, które wykorzystują pomiary składowych prędkości liniowych obiektu w układzie związanym z ziemią oraz kąty orientacji obiektu. Oba te pomiary są dostępne w systemie nawigacji inercjalnej, a jeden z nich, pomiar prędkości, w systemie nawigacji satelitarnej. Przedstawiono koncepcję wykorzystania nawigacji inercjalnej i satelitarnej do estymacji kąta natarcia. Praktyczne porównanie takiej metody z pomiarem skrzydełkowym czujnikiem kąta natarcia dokonano na samolocie Iryda. Przedstawiono również propozycje rozwinięcia tych metod.

EN

The paper presents problems of angle of attack estimation on flying object board. There are in detail presented angle of attack estimation methods which are applying measurements of linear velocities components of object at the Earth coordinates and attitude angles of object. Both of these measurements are inertial navigation system origin, and one of them, velocity measurement, is satellite navigation system origin. Idea of use making of inertial and satellite navigation for angle of attack estimation is depicted. The in practice comparison of this method to pivoted van method has been conducted on aircraft Iryda board. The development proposals of these methods are presented, too.

11

Dylematy wykolejeń do wewnątrz łuków

Bałuch M.

Zeszyty Naukowo-Techniczne Stowarzyszenia Inżynierów i Techników Komunikacji w Krakowie. Seria: Materiały Konferencyjne

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2010

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Nr 95, z. 154

23--38

PL

W artykule omówiono rzadki przypadek wykolejenia pojazdu szynowego do wewnątrz łuku przy małej prędkości jazdy. Skupiono się głównie na dwóch aspektach, tj. znaczeniu nadmiernego zużycia kół w ich części środkowej oraz niekorzystnym wpływie małych prędkości pociągów, które w pewnych przypadkach mogą zwiększyć ryzyko wykolejeń. Przedstawiono również przykład obliczeń kątów nabiegania na tok wewnętrzny w łuku o złym stanie utrzymania.

EN

The paper describes a rare case of a rail vehicle derailment inside a curve at low speeds. It focuses mainly on two aspects as meaning of excessive wheel wear in its middle part and bad influence of train’s low speed, which could increase the risk of derailments in some cases. The paper also presents an example of calculation of angles of attack on the low rail on the curve of a bad condition of maintenance.

12

Prediction of transonic wind tunnel test section geometry - a numerical study

Selerowicz W. C.

Archive of Mechanical Engineering

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2009

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Vol. LVI, nr 2

113-130

EN

The paper presents numerical simulations related to the problem of how to obtain correct results in transonic wind tunnel during tests at high airfoil angles of attack. At this flow conditions, significant pressure losses appear in the test section, what leads to significant errors in measured data. Regarding the possible ways of tunnel reconstruction, we examined three different possibilities of changing the test section configurations: an increase of the test section height, displacement of the airfoil below the tunnel centreline and, finally, introduction of divergent test section walls. It was shown that neither the use of higher test section, nor the change of the airfoil location, gives any significant improvement in reference to the existing tunnel configuration. Only after divergent test section walls were introduced, the distributions of pressure coefficient became well consistent with their expected values.

PL

W pracy przedstawiono studium numeryczne dotyczące wstępnego definiowania ustawienia przestrzeni pomiarowej tunelu transonicznego podczas pomiarów profili lotniczych ustawionych pod bardzo dużymi kątami natarcia. W takich przypadkach duże straty ciśnienia w tunelu, spowodowane dławieniem przepływu przez model, ślad aerodynamiczny i warstwę przyścienną na ściankach przestrzeni pomiarowej powodują znaczne błędy mierzonych wielkości. Uwzględniając konstrukcję tunelu oraz wynikające stąd ograniczenia przedstawiono różne sposoby zminimalizowania tych niepożądanych efektów. Wykorzystując symulacje numeryczną przedstawiono rozkłady ciśnień wzdłuż ścianki górnej i dolnej przestrzeni pomiarowej oraz rozkłady współczynnika ciśnienia na profilu dla różnych konfiguracji. Dla przestrzeni pomiarowej z rozbieżnymi ściankami uzyskano zadawalające wyniki, zbieżne z wynikami dla opływu w przestrzeni swobodnej.

13

Modelowanie sił i momentów sił aerodynamicznych wywołanych prędkością kątową samolotu - rozwinięcie klasycznej metody pasowej dla dużych kątów natarcia

Maryniak J., Pyrz J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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1998

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z. 6

249-254

PL

W pracy został przedstawiony sposób wyznaczania sił i momentów aerodynamicznych wywołanych prędkością kątową samolotu w oparciu o rozwinięcie klasycznej metody pasowej. Sposób wyprowadzenia wzorów pozwala na stosowanie tej metody w pełnym zakresie kątów natarcia. W celach porównawczych wyznaczono kilka bezwymiarowych współczynników i momentów sił przy pomocy prezentowanej metody oraz ESDU dla skrzydła samolot 1-22 IRYDA M93 jako obiektu testowego.

EN

This paper presents aerodynamic forces and moments of forces calculation method develop by airplane angular velocity supported by developing classical strip method. Method of derive formulas allows uses it in full range the angle of attack. We presented few dimensionless coefficients forces and moments of forces calculated by this method and ESDU for 1-22 Iryda M93 wing as a test object.