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1

Evaluation of wind effects on buildings using design codes and numerical wind tunnel tests

Hossain Imam, Islam Jahidul, Amin Al

Structure and Environment

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2023

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Vol. 15, no. 2

73--81

EN

The evaluation of wind effect on the regular shape and simple diaphragm buildings and structures due to wind load has been calculated by several international codes and standards where wind gust nature and dynamic effect could not capture. Bangladesh National Building Code (BNBC) provides the tools for engineers to calculate the wind pressures for the design of a regular-shaped structure with a height to width ratio of less than 5.0, a simple diaphragm, and no unusual geometrical irregularity. If these conditions do not satisfy a wind tunnel testing is required. In this study, a comparative study between two codes in Bangladesh (BNBC-2006 and BNBC-2020), and wind tunnel test results are conducted. An investigation is carried out on four typical buildings with variable heights located within Dhaka, Bangladesh. A computational fluid dynamics (CFD) program RWIND is used to calculate the wind loads on buildings and are compared with those obtained by Bangladesh National Building Codes. Storey shear of four different building models is compared. Between BNBC-2006 and BNBC-2020, there is up to a 53% difference in storey shear. Whereas, up to 30% variation in storey shear is observed between the numerical wind tunnel test data and the data calculated using the BNBC-2020 equations. Finally, this study will help in improving BNBC code provisions for wind load calculations.

PL

Kalkulację wpływu wiatru na budynki i budowle o regularnych kształtach i prostych konstrukcjach pod obciążeniem wiatrem przedstawiono w kilku normach międzynarodowych, w których jednak nie uwzględniono charakteru podmuchów wiatru i efektu dynamicznego. Bangladeska Krajowa Norma Budowlana (BNBC) zapewnia inżynierom narzędzia do obliczania ciśnienia wiatru przy projektowaniu konstrukcji o regularnym kształcie, o stosunku wysokości do szerokości mniejszym niż 5,0, prostej konstrukcji oraz bez nietypowych nieregularności geometrycznych. Jeśli warunki te nie są spełnione, wymagane jest przeprowadzenie testów w tunelu aerodynamicznym. W niniejszym opracowaniu przeprowadzono badanie porównawcze między dwiema normami obowiązującymi w Bangladeszu (BNBC-2006 i BNBC-2020) oraz wynikami testów w tunelu aerodynamicznym. Badanie przeprowadzono na czterech typowych budynkach o różnej wysokości zlokalizowanych w Dhace w Bangladeszu. Program RWIND do obliczeń i symulacji dynamiki płynów (CFD) został wykorzystany do obliczenia obciążeń wiatrem na budynkach i porównany z wynikami uzyskanymi według bangladeskich norm budowlanych. Porównano ścinanie kondygnacji czterech różnych modeli budynków. W tym względzie różnice pomiędzy BNBC-2006 i BNBC-2020 wynoszą do 53%. Natomiast między danymi z numerycznego testu w tunelu aerodynamicznym a danymi obliczonymi przy użyciu równań BNBC-2020 zaobserwowano do 30% różnic w odniesieniu do ścinania kondygnacji. Badanie to pomoże też ulepszyć przepisy norm BNBC dotyczące obliczeń obciążenia wiatrem.

2

Experimental and numerical analyses of airflow around two cylinders angled to the direction of wind

Padewska-Jurczak Agnieszka, Szczepaniak Piotr, Walentyński Ryszard

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 1

art. no. e144578

EN

The analyses aim to determine aerodynamic force coefficients in the case of airflow around two smooth or rough cylinders positioned at different angles to the direction of wind velocity. Such systems, for instance, may be part of a tubular water slide. The results were compared with the values of the interference coefficient of the cylinders arranged in a row included in Eurocode EN 1991 part 4. The aerodynamic forces of the cylinder systems were determined on the basis of experimental tests conducted in a wind tunnel. To verify the above results, CFD (computational fluid dynamics) simulations were prepared. An important observation is that for the angle of yaw β = 0◦, the negative component of the lift force (lateral) fy is shown, while for the other cases, the situation is opposite and the lateral force points outside the gap (upward). The second is that the results of aerodynamic drag for rough cylinders arranged in a row and calculated according to EN 1991 part 4 may be underestimated. The flow around the pair of smooth cylinders is quite different from that of the rough ones, because during the experiment the first falls into the critical flow regime, while the second has supercritical characteristics.

3

Construction and dynamic identification of aeroelastic test models for flexible roofs

Rizzo Fabio, Sadhu Ayan, Abasi Ali, Pistol Aleksander, Flaga Łukasz, Venanzi Ilaria, Ubertini Filippo

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e16, 2023

EN

The aeroelastic wind tunnel testing of flexible roofs made of hyperbolic paraboloid cable nets is a challenging task for designers and researchers, with very limited documented experiences in the literature. The reduced-scale model construction and its dynamic identification are the main issues to address when approaching this problem, mainly because of (i) the very small mass of the roof, (ii) the strict aeroelastic criteria to satisfy and (iii) a large number of very closely spaced significant natural frequencies. To suggest an approach to follow to investigate the wind-structure interaction for this structural typology, this paper discusses the aeroelastic scaling, the aeroelastic model construction, the dynamic modal identification and the FEM predictive numerical modelling of hyperbolic paraboloid roofs (HPRs) with square, rectangular and circular plan shapes and two different curvatures. Modal identification is especially challenging due to the presence of several closely spaced modes and it is here tackled by different methods such as Welch’s method, random decrement technique (RDT), Empirical mode decomposition with a time-varying filter (TVF-EMD) and frequency domain decomposition method (FDD). The satisfying accuracy of the aeroelastic scaling has been verified by comparing the wind-induced vertical displacements of the prototypes against those of the experimental models. Furthermore, an extensive qualitative investigation of the natural mode shapes has been carried out revealing that test models reproduce most of the prototype modes.

4

Wind tunnel experiment of multi-mode arc sail device

Zhang Huawu, Hu Yihuai, He Jianhai

Polish Maritime Research

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2021

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nr 4

20--29

EN

A ship’s wind energy utilization device with multi-mode arc-shaped sails is designed, which have different working modes for sail-assisting or wind power generation according to the ship’s navigation. The structural characteristics and working principles of this device are firstly described in this paper. Three sets of arc-shaped sails with different thickness (4.5 cm, 11.3 cm, 21.7 cm) were designed. Wind tunnel experiments were carried out in the respects of sail-assisting performance and wind-power generation to determine the best sail blade shape and to verify the energy-saving effect of this device. Experiments show that the sail with the smallest thickness (4.5 cm) has a better boosting effect than others, and the sail with the largest thickness (21.7 cm) has the best wind power generation performance. Considering the lateral force and the structural strength of the support, in the case of the comprehensive evaluation for the boosting and power generation performance, it is considered that the intermediate thickness (11.3 cm) is the best choice. The device has a good comprehensive energy utilization effect and has development and application value.

5

Model tests of global stability of two types of lightning protection masts under wind action

Flaga Andrzej, Kłaput Renata, Kocoń Agnieszka

Technical Transactions

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2019

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Vol. 116, iss. 1

93--112

EN

The paper presents results of wind tunnel experiments of wind action on two free-standing lighting protection masts: cantilevered and tripod. Own similarity criteria concerning phenomenon of global stability loss were used in these tests. It was determined whether masts fulfill the requirements of overturning and shift global stability in range of base wind velocities adequate for Poland and different categories of terrain roughness according to the Eurocode [13]. Two possible forms of the loss of the global stability of lighting protection masts in strong wind were considered: overturning a mast and shifting of mast as a whole structures. The measurements were conducted for eight directions of wind attack, five positions of masts on the roof, two settings of the mast for tripod mast and one for cantilevered mast, two categories of terrain roughness. Conducted tests allowed to determine whether it is safe to locate tripod mast in all wind zones in Poland. Cantilevered mast can be located safely in I and II wind zone in Poland.

PL

W artykule przedstawione zostały wyniki badań oddziaływania wiatru na dwa wolnostojące maszty odgromowe: pojedynczy i na trójnogu. W badaniach tych zastosowano własne kryteria podobieństwa dotyczące zjawiska globalnej utraty stateczności. Określono, czy maszty spełniają warunki stateczności globalnej na obrót i przesuw w zakresie prędkości bazowych wiatru adekwatnych dla Polski i różnych kategorii chropowatości terenu według Eurokodu [13]. Rozpatrywano dwie możliwe formy utraty globalnej stateczności masztów przy silnym wietrze: wywrócenie masztu (jako całości) i przesunięcie masztu (jako całości). Pomiary przeprowadzono dla ośmiu kierunków natarcia wiatru, pięciu położeń masztu na dachu, dwóch ustawień masztu na trójnogu i jednego ustawienia masztu pojedynczego, dwóch kategorii chropowatości terenu. Przeprowadzone badania pozwoliły na stwierdzenie, czy bezpiecznie jest ustawić maszt na trójnogu we wszystkich strefach wiatrowych w Polsce. Wykazano, że maszt pojedynczy może być ustawiony w I i II strefie wiatrowej w Polsce.

6

Wind tunnel tests of wind pressure distributions for four different tent halls

Flaga A., Kłaput R., Kocoń A.

Technical Transactions

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2018

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Vol. 115, iss. 3

91--105

EN

This papers concerns measurements of wind pressure distributions on the roofs and side walls of tent hall models. Four tent halls of different shapes and constructions were investigated in the boundary layer wind tunnel at Cracow University of Technology, Poland. On the basis of these measurements, different schemes of wind pressure coefficient distributions for these structures were determined, including mean and extreme values of the coefficients. The obtained results, their analyses and comparisons are of great importance from a structural design point of view for such types of structures.

PL

Praca zawiera wyniki badań rozkładu ciśnienia wiatru na dachach i ścianach bocznych hal namiotowych. W tunelu aerodynamicznym Politechniki Krakowskiej przebadano cztery hale namiotowe różnych kształtów. Na podstawie tych pomiarów określono schematy rozkładów współczynników ciśnienia wiatru oraz średnie i ekstremalne wartości współczynników. Otrzymane wyniki oraz ich analizy i porównania mają duże znaczenie z punktu widzenia projektowania tego typu konstrukcji.

7

Experimental and computational studies of stall on a helicopter rotor airfoil

Surmacz K.

Journal of KONES

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2016

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Vol. 23, No. 3

511--517

EN

In the case of forward flight of a helicopter, the flow field around rotating blades of a rotor is highly threedimensional and very complex. Helicopter blades work across a wide range of angles of attack and airspeed. The stall occurs on the retreating blade in forward flight and causes dissymmetry of lift on a rotor disc. The investigation of the stall phenomenon has been performed using experimental and computational methods. Experimental analysis was made at the Ohio State University 6’’x 22’’ unsteady transonic wind tunnel. Research in the wind tunnel was performed using two methods: oil visualization (over a wide range of alpha and Ma) and pressure measurements. Computational part of the research has been done using Computational Fluid Dynamics tool. 2- and 3-dimensional calculations performed using ANSYS FLUENT software. In both experimental and computational cases, the 3D flow around a section of a rotor blade based on the SSC-A09 airfoil was analysed. The test article of the research was a section, which was located in the tip region of the main rotor blade of UH-60M Black Hawk helicopter. The research was conducted for a wide range of angles of attack and at several velocities. The most interesting part of the analysis concerned on unsteady flow conditions corresponding to stall.

8

Model tests of wind turbines in wind tunnels

Flay R. G. J.

Czasopismo Techniczne. Budownictwo

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2015

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Y. 112, iss. 2-B

63--81

EN

This paper describes methods for testing model wind turbines in wind tunnels based on published data and the experience gained by the author through having tested many different wind turbines in wind tunnels at the University of Auckland. Wind tunnels can be used to determine the performance of small wind turbines at full scale, or larger wind turbines at reduced scale. Such experiments need to be done with care as one needs to be aware of issues regarding blockage, the effect of Reynolds number, and being able to control the speed of the turbine so that is power coefficient can be obtained over a suitable range of tip speed ratios. With rotating machinery, it is also important to have a regard to safety, so the models have to be made with care and a stress analysis carried out to ensure that the material properties are not exceeded during the testing. It is found that wind tunnel testing is a useful way of determining experimentally the performance of wind turbines in order to predict the power output, and for obtaining data to validate theoretical or numerical model predictions.

PL

W poniższym artykule opisano metody testowania modeli turbin wiatrowych w tunelach aerodynamicznych na podstawie opublikowanych danych oraz doświadczenia autora uzyskanego w wyniku badań wielu turbin wiatrowych przeprowadzonych w tunelach aerodynamicznych Uniwersytetu w Auckland. Tunele aerodynamiczne mogą być wykorzystywane do wyznaczania wydajności małych turbin wiatrowych w pełnej skali, albo większych turbin w skali zredukowanej. Takie doświadczenia muszą być przeprowadzane bardzo starannie, ze zwróceniem uwagi na takie problemy, jak efekt blokady, efekt liczby Reynoldsa. Trzeba także mieć możliwość kontrolowania prędkości turbiny, tak aby współczynnik mocy mógł być uzyskany w odpowiednim zakresie współczynnika szybkobieżności. W przypadku maszyn wirnikowych ważne jest zapewnienie bezpieczeństwa, tak aby modele były wykonane z należytą starannością na podstawie przeprowadzonej wcześniej analizy wytrzymałościowej, co pozwala upewnić się, że odpowiednie charakterystyki materiałowe nie zostaną przekroczone w trakcie badań. Stwierdzono, że badania w tunelu aerodynamicznym to użyteczna metoda doświadczalnego wyznaczania wydajności turbin wiatrowych. Pozwalają one przewidzieć moc wyjściową oraz inne dane umożliwiające walidację modeli teoretycznych i numerycznych.

9

Aerodynamics of small wind turbine: a new game on old ground

Izmaylov R. A., Dudnikov S. Y., Lebedev A. A., Khoroshev E. N., Chumakov Y. S., Melnikov Y. B.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2011

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nr 140

97-104

EN

A new design of small wind turbine is presented. The proposed system consists of axial flow turbine, located in aerodynamically profiled ring shroud, and modern alternating current generator. Results of CFD three-dimensional modeling of the system operation are presented. System prototype (diameter 0.5 m) was tested in open air on a moving car and in wind tunnel of SPSTU. Experiments were carried out at different air velocities with the measurements of flow using hotwire anemometer and pressure pick-ups. The results confirm preliminary estimations and open possibilities to produce small wind turbine up to diameter 10m.

10

Advanced dynamic methods for structural evaluation of TV towers

Osterrieder P., Beirow B.

Zeszyty Naukowe. Budownictwo / Politechnika Opolska

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2003

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z. 47

103-115

EN

On the background of the demand for an extended transmission capacity, the principles of static and dynamie behaviour of reinforced TV and telecommunication towers were investigated exemplarily at the Cottbus tower. The experimental part of the investigations is based on wind tunnel tests and permanent long-time measurements by a monitoring system acquiring data of wind situation and vibration velocity. The numerical part of the investigations was covered by conventional stochastic and deterministic methods for the calculation of the structural response due to along-wind and vortex shedding as well as by a new, hybrid and more close to reality numerical method based on neural networks. It could be shown that the serviceability of the Cottbus tower is actually not subjected to danger. The largest inclinations concerning permanent operation of transmission facilities result from along-wind and nonuniform temperature loadings over the shafts cross-section. As the most critical loading, with regard to questions of comfort and long-time behaviour, vortex shedding at the aerial antenna could be identified. Moreover, considerable reserves with a view to an extension of transmission facilities could be proved. Nevertheless, it was shown that these extensions cause a considerable increase in along-wind loadings, which could effect a critical structural response in case of towers having a lower stiffness. In order to avoid any risk from the outset, a strategy for planning operational changes was proposed on principle.

11

Wpływ komór wyrównawczych przestrzeni pomiarowej na właściwości tunelu aerodynamicznego

Knap T.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2000

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nr 117, vol. 2

207-212

PL

W tunelach aerodynamicznych o zamkniętych PP i stałym poprzecznym przekroju następuje zmniejszenie przekroju strumienia spowodowane obecnością modelu oraz narastającej grubości warstwy przyściennej na ściankach tunelu. Występuje wzrost prędkości przepływu i ujemny gradient ciśnienia statycznego. Czynniki te zmieniają własności opływowe badanych modeli zarówno statyczne jak i dynamiczne. W pracy przedstawiono wyniki badań eksperymentalnych wpływu komór wyrównawczych na wyniki pomiarów w tunelach aerodynamicznych.

EN

The presence of model in closed test section of wind tunnel causes blockage effect of the test section. The reduction of effective section of stream core results in increase of mean velocity, and hence in negative gradient of pressure. This results in change of pressure distribution on body surface, and so-called buoyancy drag. One of possible methods of the effect is application of the slotted test section, connected with compensation chambers. The paper presents results of investigation of influence of compensation chambers on static pressure gradient in test section and its influence on drag of spheres and circular cylinders placed in the test section.