Artigos de revistas: "Bluff bodie"

1

KIYA, Masaru, Hitoshi ISHIKAWA e Osamu MOCHIZUKI. "Aerodynamics of Three-dimensional Bluff Bodie". Wind Engineers, JAWE 2000, n.º 83 (2000): 11–18. http://dx.doi.org/10.5359/jawe.2000.83_11.

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Herrera, P. A., L. G. Closs e M. L. Silberman. "Alteration and geochemical zoning in Bodie Bluff, Bodie mining district, eastern California". Journal of Geochemical Exploration 48, n.º 2 (julho de 1993): 259–75. http://dx.doi.org/10.1016/0375-6742(93)90007-9.

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3

Dalbir Singh, Dalbir Singh, M. M. Gaud M.M. Gaud e Jaswinder Singh Jaswinder Singh. "Fundamental Control of Wake Behind Bluff Bodies : A Review". International Journal of Scientific Research 2, n.º 8 (1 de junho de 2012): 134–35. http://dx.doi.org/10.15373/22778179/aug2013/45.

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4

Wygnanski, Israel. "ON ACTIVE CONTROL OF SEPARATION FROM BLUFF BODIES(Keynote Lecture)". Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF) 2005 (2005): 15–24. http://dx.doi.org/10.1299/jsmeicjwsf.2005.15.

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5

Teimourian, Amir, e Hanifa Teimourian. "Vortex Shedding Suppression: A Review on Modified Bluff Bodies". Eng 2, n.º 3 (27 de julho de 2021): 325–39. http://dx.doi.org/10.3390/eng2030021.

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Vortex shedding phenomenon behind bluff bodies and its destructive unsteady wake can be controlled by employing active and passive flow control methods. In this quest, researchers employed experimental fluid dynamics (EFD), computational fluid dynamics (CFD) and an analytical approach to investigate such phenomena to reach a desired outcome. This study reviews the available literature on the flow control of vortex shedding behind bluff bodies and its destructive wake through the modification of the geometry of the bluff body. Various modifications on the bluff body geometries namely perforated bluff bodies, permeable and porous mesh, corner modification and wavy cylinder have been reviewed. The effectiveness of these methods has been discussed in terms of drag variation, wake structure modifications and Strouhal number alteration.

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6

Thompson, Mark C., Thomas Leweke e Kerry Hourigan. "Bluff Bodies and Wake–Wall Interactions". Annual Review of Fluid Mechanics 53, n.º 1 (5 de janeiro de 2021): 347–76. http://dx.doi.org/10.1146/annurev-fluid-072220-123637.

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This review surveys the dramatic variations in wake structures and flow transitions, in addition to body forces, that appear as the motion of bluff bodies through a fluid occurs increasingly closer to a solid wall. In particular, we discuss the two cases of bluff bodies translating parallel to solid walls at varying heights and bluff bodies impacting on solid walls. In the former case, we highlight the changes to the wake structures as the flow varies from that of an isolated body to that of a body on or very close to the wall, including the effects when the body is rotating. For the latter case of an impacting body, we review the flow structures following impact and their transition to three-dimensionality. We discuss the issue of whether there is solid–solid contact between the bluff body and a wall and its importance to body motion.

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7

Mat Ali, Mohamed Sukri, Sheikh Ahmad Zaki Shaikh Salim, Mohamad Hafz Ismail, Sallehuddin Muhamad e Muhammad Iyas Mahzan. "Aeolian Tones Radiated from Flow Over Bluff Bodies". Open Mechanical Engineering Journal 7, n.º 1 (18 de outubro de 2013): 48–57. http://dx.doi.org/10.2174/1874155x01307010048.

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Bluff body is a simple but a central shape for many engineering applications. The geometry shape of the bluff body characterises the behaviour of the flow over the bluff body, where a more complex flow structure is found near downstream. Shear layer separation is mainly responsible for the periodic global phenomena, that includes the generation of sound. The magnitude of the aerodynamically generated sound is dominated by the fluctuations of aerodynamics forces, i.e., drag and lift. The study also shows that the sound pressure field is shaped by the aeolian tones that is related strongly to the lift fluctuations of the bluff body. Amplitude and frequency of the fluctuating lift change naturally with the shape of a particular bluff body. Triangular cylinder exhibits the largest sound pressure level (41.9 dB) followed by ellipse and circular shapes. Square cylinder emits the lowest sound pressure level (36.7 dB). This corresponds to the longest downstream vortex formation length at which for a square cylinder the long vortex formation length provides space for more vortex to dissipate.

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8

Sarioglu, Mustafa, e Tahir Yavuz. "Subcritical Flow Around Bluff Bodies". AIAA Journal 40, n.º 7 (julho de 2002): 1257–68. http://dx.doi.org/10.2514/2.1792.

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Abdullah, Makola M., Kenneth K. Walsh, Shannon Grady e G. Dale Wesson. "Modeling Flow around Bluff Bodies". Journal of Computing in Civil Engineering 19, n.º 1 (janeiro de 2005): 104–7. http://dx.doi.org/10.1061/(asce)0887-3801(2005)19:1(104).

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10

Matsumoto, Masaru, Yoshiyuki Daito, Fumitaka Yoshizumi, Yasuo Ichikawa e Tadahiro Yabutani. "Torsional flutter of bluff bodies". Journal of Wind Engineering and Industrial Aerodynamics 69-71 (julho de 1997): 871–82. http://dx.doi.org/10.1016/s0167-6105(97)00213-4.

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Sarioglu, M., e T. Yavuz. "Subcritical flow around bluff bodies". AIAA Journal 40 (janeiro de 2002): 1257–68. http://dx.doi.org/10.2514/3.15221.

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12

Mollamahdi, Mahdi, e Seyed Abdolmehdi Hashemi. "A numerical study on the flame characteristics and pollutant emissions in a premixed burner: Comparison between porous and solid bluff bodies". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 234, n.º 3 (15 de julho de 2019): 353–64. http://dx.doi.org/10.1177/0957650919861839.

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The effects of porous and solid bluff bodies in the combustion chamber on flame stability limits, gas and solid temperature distributions, pressure drop, methane conversion rate, and CO and NO emissions are examined numerically. The porous and solid bluff bodies are made of SiC with the inner diameter of 50 mm, the outer diameter of 90 mm, and the length of 22 mm. In this study, Renormalization Group k–ε is used for modeling of turbulence. Eddy dissipation concept is selected for modeling of the interaction between turbulence and chemistry. A reduced mechanism based on GRI 3.0 consisting of 16 species and 41 reactions is employed to model methane combustion. The results indicate that the upper flame stability limit can be diminished by adding porous bluff body in the combustion chamber instead of the solid bluff body. Besides, the pressure drop, CO and NO emissions in the combustion chamber with solid bluff body are higher than those of porous bluff body, while the methane conversion rate increases by replacing porous bluff body instead of solid bluff body in the combustion chamber.

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13

Siddiqui, Naseeb Ahmed, e Martin Agelin-Chaab. "Nature-inspired solutions to bluff body aerodynamic problems: A review". Journal of Mechanical Engineering and Sciences 15, n.º 2 (10 de junho de 2021): 8095–140. http://dx.doi.org/10.15282/jmes.15.2.2021.13.0638.

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This review investigates the nature-inspired techniques for the optimization of the aerodynamic forces on bluff bodies. To provide a rich understanding of these nature-inspired phenomena, three distinct zones of the species fishes (nektons), birds (avians) and the fast running land animals are considered. This allows contextualizing different capabilities of the species in different environmental necessities. The review follows a trend in which drag reduction capabilities of individual parts of these species, including body shape & size, tails, fins, surface structure, wings, and wingtips, have been explored in detail. By focusing on specific parts, the review examined the methods and physics involved, which provides space to narrate the development of ideas and our current understanding of the nature-inspired drag reduction and their application to bluff body aerodynamics. Consequently, nature-inspired promising areas for future endeavor related to the bluff body has been discussed in detail. It was found that, though, aerospace field has found several bird inspired application but the bluff body flow modification have only few. Similar is the case with fishes and land animals which have not been explored yet for aerodynamic use on the bluff bodies. The crucial importance of passive devices are also highlighted along with the review of their application on the bluff bodies inspired by nature. Furthermore, several of nature-inspired techniques are proposed and compared to facilitate the research in this direction. It provides a fundamental method to develop nature-inspired flow control devices for the bluff bodies.

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14

Bhattacharjee, Somnath, Arindam Mandal, Rabin Debnath e Snehamoy Majumder. "Experimental Investigation of the Effect of Single and Twin Bluff Bodies on the Turbulent Flow in an Asymmetric Rectangular Diffuser". International Journal on Applied Physics and Engineering 1 (31 de dezembro de 2022): 48–59. http://dx.doi.org/10.37394/232030.2022.1.7.

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Experimental investigation of the effect of bluff bodies on the turbulent flow through an asymmetric diffuser has been carried out. The rectangular diffuser is designed and made keeping similarity to that used by Buice and Eaton, [1], having an inclination angle of 10°. Three geometrical configurations have been selected for the experimentation. (I) At first the experiment has been carried out for the validation of the present results with Buice and Eaton, [1], placing no bluff body at all. (II) Thereafter measurements have been carried out by placing a single bluff body on the horizontal floor of the diffuser to estimate the effect of the bluff body on the downstream flow. (III) Finally, two identical bluff bodies are placed on the horizontal floor of the diffuser and experimental work has been carried out in order to investigate the effect of the existence of two bluff bodies on the downstream flow through the diffuser. The present results agree well with the results of Buice and Eaton, [1], to show that the recirculation zone appears just adjacent to the inclined plane when there is no bluff body in a diffuser. Also, the detailed investigation for velocity of flow field, distribution of skin friction factor along with uncertainty analysis as well as the correlation between friction factor and Reynolds Number have been carried out in the research paper.

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15

Balachandar, R., e A. S. Ramamurthy. "Blockage Effects on Cavitation Inception Characteristics of Bluff Bodies". Proceedings of the Institution of Mechanical Engineers, Part C: Mechanical Engineering Science 205, n.º 6 (novembro de 1991): 415–19. http://dx.doi.org/10.1243/pime_proc_1991_205_139_02.

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The study deals with the prediction of cavitation inception in the wake of two-dimensional bluff bodies subject to wall interference effects. Corrections are included in the model to account for flow entrainment effects and loss of circulation in the vortices shed from the bluff body. Experimental results are also presented to verify the proposed model over a range of blockages.

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16

NISHIO, Shun, Kouko HORIKAWA e Hitoshi ISHIKAWA. "Flow Visualization of Axisymmetric Bluff Bodies". Proceedings of Conference of Kanto Branch 2021.27 (2021): 10D15. http://dx.doi.org/10.1299/jsmekanto.2021.27.10d15.

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17

Hangan, H., e B. J. Vickery. "Buffeting of two-dimensional bluff bodies". Journal of Wind Engineering and Industrial Aerodynamics 82, n.º 1-3 (agosto de 1999): 173–87. http://dx.doi.org/10.1016/s0167-6105(99)00003-3.

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18

Nakamura, Yasuharu, e Katsuya Hirata. "Critical geometry of oscillating bluff bodies". Journal of Fluid Mechanics 208 (novembro de 1989): 375–93. http://dx.doi.org/10.1017/s0022112089002879.

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Measurements are presented of the mean pressures around rectangular and D-section cylinders, with a flat front face normal to the flow, forced to oscillate transversely at an amplitude of 10% of the length of the front face. The ratio of depth (streamwise dimension) to height (cross-stream dimension) of the cross-section ranges from 0.2 to 1.0 for rectangular cylinders and from 0.5 to 1.5 for D-section cylinders. The range of reduced velocities investigated, 3 to 11, includes the vortex-resonance region. When increasing the depth, an oscillating bluff cylinder shows a critical depth where base suction attains a peak. The value of a critical depth is lowered with decreasing reduced velocity. In particular, an extraordinarily low critical depth with a very high base suction is obtained on cylinders oscillating at vortex resonance. For cylinders with depths beyond the critical, a reattachment-type pressure distribution is established on the afterbody due to the shear-layer/edge direct interaction. The shear-layer/edge direct interaction can also occur on oscillating cylinders with a fixed splitter plate. At low reduced velocities, the reattachment-type pressure distributions on cylinders with and without a splitter plate are similar except for the mean level. A remark is made on the critical geometry of bluff bodies under various flow conditions.

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19

Prud'homme, Simon, Frederic Legeron e Andre Laneville. "Transient flutter analysis of bluff bodies". Journal of Wind Engineering and Industrial Aerodynamics 145 (outubro de 2015): 139–51. http://dx.doi.org/10.1016/j.jweia.2015.06.013.

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20

Royles, Rodney, e Jun Kanda. "Alongwind dynamic effects on bluff bodies". Strain 24, n.º 2 (maio de 1988): 57–65. http://dx.doi.org/10.1111/j.1475-1305.1988.tb00003.x.

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21

Leweke, T., L. Schouveiler, M. C. Thompson e K. Hourigan. "Unsteady flow around impacting bluff bodies". Journal of Fluids and Structures 24, n.º 8 (novembro de 2008): 1194–203. http://dx.doi.org/10.1016/j.jfluidstructs.2008.08.003.

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22

Fang, Xingjun, e Mark F. Tachie. "Flows over surface-mounted bluff bodies with different spanwise widths submerged in a deep turbulent boundary layer". Journal of Fluid Mechanics 877 (27 de agosto de 2019): 717–58. http://dx.doi.org/10.1017/jfm.2019.617.

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The spatio-temporal dynamics of separation bubbles induced by surface-mounted bluff bodies with different spanwise widths and submerged in a thick turbulent boundary layer is experimentally investigated. The streamwise extent of the bluff bodies is fixed at 2.36 body heights and the spanwise aspect ratio ($AR$), defined as the ratio between the width and height, is increased from 1 to 20. The thickness of the upstream turbulent boundary layer is 4.8 body heights, and the dimensionless shear and turbulence intensity evaluated at the body height are 0.23 % and 15.8 %, respectively, while the Reynolds number based on the body height and upstream free-stream velocity is 12 300. For these upstream conditions and limited streamwise extent of the bluff bodies, two distinct and strongly interacting separation bubbles are formed over and behind the bluff bodies. A time-resolved particle image velocimetry is used to simultaneously measure the velocity field within these separation bubbles. Based on the dynamics of the mean separation bubbles over and behind the bluff bodies, the flow fields are categorized into three-dimensional, transitional and two-dimensional regimes. The results indicate that the low-frequency flapping motions of the separation bubble on top of the bluff body with $\mathit{AR}=1$ are primarily influenced by the vortex shedding motion, while those with larger aspect ratios are modulated by the large-scale streamwise elongated structures embedded in the oncoming turbulent boundary layer. For $\mathit{AR}=1$ and 20, the flapping motions in the wake region are strongly influenced by those on top of the bluff bodies but with a time delay that is dependent on the $AR$. Moreover, an expansion of the separation bubble on the top surface tends to lead to an expansion and contraction of separation bubbles in the wake of $\mathit{AR}=20$ and 1, respectively. As for the transitional case of $\mathit{AR}=8$, the separation bubbles over and behind the body are in phase over a wide range of time difference. The dynamics of the shear layer in the wake region of the transitional case is remarkably more complex than the limiting two-dimensional and three-dimensional configurations.

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23

Umyshev, Dias, Abay Dostiyarov, Andrey Kibarin, Galya Tyutebayeva, Gaziza Katranova e Darkhan Akpanbetov. "Experimental investigation of distance between v-gutters on flame stabilization and NOx emissions". Thermal Science 23, n.º 5 Part B (2019): 2971–81. http://dx.doi.org/10.2298/tsci180503007u.

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Blow-off performance and NOx emissions of the propane and air mixture in a rectangular combustion chamber with bluff bodies were investigated experimentally and numerically. The effects of distance between bluff bodies on NOx emissions, the blow-off limit, and exhaust gas temperature were examined. It was observed that NOx emissions are highly dependent on distance between V-gutters. The re-circulation zone behind the bluff body expands in width based on the decrease of distance between V-gutters, and expands in length with the increase of inlet velocity. The temperature fields behind the bluff body show a similar change, the temperature behind the bluff body reaches its highest when the distance between V-gutters reaches 20 mm, meaning it has better flame stability. The blow-off limit is significantly improved with the decrease of distance between V-gutters. The blow-off limit is greatly improved by reducing the distance between the V-gutters. Maximum blow-off limit of 0.11 is reached in the case of 20 mm, compared with 0.16 at 50 mm at a speed of 10 m/s.

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24

Triyogi, Y., D. Suprayogi e E. Spirda. "Reducing the drag on a circular cylinder by upstream installation of an I-type bluff body as passive control". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 223, n.º 10 (5 de junho de 2009): 2291–96. http://dx.doi.org/10.1243/09544062jmes1543.

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The bluff body cut from a small circular cylinder that is cut at both sides parallel to the y-axis was used as passive control to reduce the drag of a larger circular cylinder. The small bluff body cut is called an I-type bluff body, which interacts with a larger one downstream. I-type bluff bodies with different cutting angles of θs = 0°(circular), 10°, 20°, 30°, 45°, 53°, and 65° were located in front and at the line axis of the circular cylinder at a spacing S/ d = 1.375, where their cutting surfaces are perpendicular to the free stream velocity vector. The tandem arrangement was tested in a subsonic wind tunnel at a Reynolds number (based on the diameter d of the circular cylinder and free stream velocity) of Re = 5.3×104. The results show that installing the bluff bodies (circular or sliced) as a passive control in front of the large circular cylinder effectively reduces the drag of the large cylinder. The passive control with cutting angle θs = 65° gives the highest drag reduction on the large circular cylinder situated downstream. It gives about 0.52 times the drag of a single cylinder.

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25

MIYATA, Masafumi. "0120 Aerodynamic Sound Emitted from Bluff Bodies". Proceedings of the Fluids engineering conference 2009 (2009): 43–44. http://dx.doi.org/10.1299/jsmefed.2009.43.

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26

Ramamurthy, A. S., R. Balachandar e Diep Ngoc Vo. "Blockage Correction for Sharp‐Edged Bluff Bodies". Journal of Engineering Mechanics 115, n.º 7 (julho de 1989): 1569–76. http://dx.doi.org/10.1061/(asce)0733-9399(1989)115:7(1569).

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27

Mittal, Sanjay, Satya Prakash Singh, Bhaskar Kumar e Rahul Kumar. "Flow past bluff bodies: effect of blockage". International Journal of Computational Fluid Dynamics 20, n.º 3-4 (março de 2006): 163–73. http://dx.doi.org/10.1080/10618560600789735.

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28

YOKOTA, Rio, Norihiko TOKAI e Shinnosuke OBI. "Vortex flow simulation of multiple bluff bodies". Proceedings of The Computational Mechanics Conference 2004.17 (2004): 731–32. http://dx.doi.org/10.1299/jsmecmd.2004.17.731.

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29

Tsai, Chou-Jiu, e Ger-Jyh Chen. "Numerical Investigation of Flow Around Bluff Bodies". Journal of Mechanics 14, n.º 3 (setembro de 1998): 153–59. http://dx.doi.org/10.1017/s1727719100000186.

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ABSTRACTIn this study, fluid flow around bluff bodies are studied to examine the vortex shedding phenomenon in conjuction with the geometrical shapes of these vortex shedders. These flow phenomena are numerically simulated. A finite volume method is employed to solve the incompressible two-dimensional Navier-Stokes equations. Thus, quantitative descriptions of the vortex shedding phenomenon in the near wake were made, which lead to a detailed description of the vortex shedding mechanism. Streamline contours, figures of lift coefficent, and figures of drag coefficent in various time, are presented, respectively, for a physical description.

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30

ZANNETTI, LUCA. "Vortex equilibrium in flows past bluff bodies". Journal of Fluid Mechanics 562 (14 de agosto de 2006): 151. http://dx.doi.org/10.1017/s0022112006001054.

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31

Leder, A., e D. Geropp. "Analysis of Unsteady flows past bluff bodies". Journal of Wind Engineering and Industrial Aerodynamics 49, n.º 1-3 (dezembro de 1993): 329–38. http://dx.doi.org/10.1016/0167-6105(93)90028-m.

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32

Wang, Lei, Mirko Salewski, Bengt Sundén, Andreas Borg e Hans Abrahamsson. "Endwall convective heat transfer for bluff bodies". International Communications in Heat and Mass Transfer 39, n.º 2 (fevereiro de 2012): 167–73. http://dx.doi.org/10.1016/j.icheatmasstransfer.2011.10.006.

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33

Gowda, B. H. L., H. J. Gerhardt e C. Kramer. "Pressure field around three-dimensional bluff bodies". Applied Scientific Research 42, n.º 3 (1985): 245–63. http://dx.doi.org/10.1007/bf00539343.

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MATSUMOTO, M. "VORTEX SHEDDING OF BLUFF BODIES: A REVIEW". Journal of Fluids and Structures 13, n.º 7-8 (outubro de 1999): 791–811. http://dx.doi.org/10.1006/jfls.1999.0249.

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Wolochuk, M. C., M. W. Plesniak e J. E. Braun. "The Effects of Turbulence and Unsteadiness on Vortex Shedding From Sharp-Edged Bluff Bodies". Journal of Fluids Engineering 118, n.º 1 (1 de março de 1996): 18–25. http://dx.doi.org/10.1115/1.2817501.

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Motivated by a desire to evaluate vortex shedding flow meters for measuring velocity in unsteady turbulent flow applications, the objective of our work was to study the effects of flow disturbances on vortex shedding from sharp-edged bluff bodies. In particular, the combined effects of turbulence and unsteadiness were examined, as well as their separate effects using controlled wind tunnel tests. After causing an initial and sudden decrease in the Strouhal number, increasing turbulence intensity from 2.5 to 10 percent resulted in only a 2.4 percent increase in the Strouhal number, for turbulence with a length scale of 0.5 bluff body diameters. Turbulence integral length scale had a significant influence on the Strouhal number, with the greatest effect exhibited for length scales near 3 bluff body diameters. Turbulence of this length scale caused a 26 percent decrease in the Strouhal number, as compared to a low-turbulence base case. Fluctuating pressure amplitude and signal-to-noise ratio were also affected by turbulence, and decreased significantly when the integral length Kali was increased from 0.25 to 0.75 bluff body diameters for a turbulence intensity of 10 percent. Unsteadiness caused lock-on for forcing at the Strouhal frequency, twice and four times the Strouhal frequency, while no lock-on was observed for forcing at half the Strouhal frequency. The range of lock-on increased with increasing perturbation amplitude and was asymmetric about the resonant frequency. For the cases investigated, the effects of combined turbulence and unsteadiness were additive, with the turbulence shifting the Strouhal frequency, and the unsteadiness causing lock-on about the shifted Strouhal frequency. The results of this study suggest that vortex shedding flow meters should be calibrated in turbulent flows and turbulence length scale must be controlled at the bluff body. Lock-on can be avoided by sizing the bluff body so that the shedding frequency is always much greater than any disturbance frequency in the flow.

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Gajewska, Karolina, Paweł Niegodajew, Renata Gnatowska e Witold Elsner. "Effect of the upstream cylinder shape on the flow around the downstream rectangular object in tandem configuration". Journal of Physics: Conference Series 2367, n.º 1 (1 de novembro de 2022): 012022. http://dx.doi.org/10.1088/1742-6596/2367/1/012022.

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Abstract The paper presents an experimental investigation of air flow around bluff bodies in tandem configurations. The first one concerns two square cylinders and in the second one a triangular cylinder was used as an upstream object. Experiment was performed for two different Reynolds number for the fixed distance between bluff bodies. To have an insight into the fluid flow, particle image velocimetry method was used. Particular attention was paid to examine the effect of the upstream cylinder shape on the flow around the downstream body.

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Brackston, R. D., J. M. García de la Cruz, A. Wynn, G. Rigas e J. F. Morrison. "Stochastic modelling and feedback control of bistability in a turbulent bluff body wake". Journal of Fluid Mechanics 802 (10 de agosto de 2016): 726–49. http://dx.doi.org/10.1017/jfm.2016.495.

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A specific feature of three-dimensional bluff body wakes, flow bistability, is a subject of particular recent interest. This feature consists of a random flipping of the wake between two asymmetric configurations and is believed to contribute to the pressure drag of many bluff bodies. In this study we apply the modelling approach recently suggested for axisymmetric bodies by Rigaset al.(J. Fluid Mech., vol. 778, 2015, R2) to the reflectional symmetry-breaking modes of a rectilinear bluff body wake. We demonstrate the validity of the model and its Reynolds number independence through time-resolved base pressure measurements of the natural wake. Further, oscillating flaps are used to investigate the dynamics and time scales of the instability associated with the flipping process, demonstrating that they are largely independent of Reynolds number. The modelling approach is then used to design a feedback controller that uses the flaps to suppress the symmetry-breaking modes. The controller is successful, leading to a suppression of the bistability of the wake, with concomitant reductions in both lateral and streamwise forces. Importantly, the controller is found to be efficient, the actuator requiring only 24 % of the aerodynamic power saving. The controller therefore provides a key demonstration of efficient feedback control used to reduce the drag of a high-Reynolds-number three-dimensional bluff body. Furthermore, the results suggest that suppression of large-scale structures is a fundamentally efficient approach for bluff body drag reduction.

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Modi, V. J., E. Shih, B. Ying e T. Yokomizo. "Drag reduction of bluff bodies through momentum injection". Journal of Aircraft 29, n.º 3 (maio de 1992): 429–36. http://dx.doi.org/10.2514/3.46179.

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Péntek, Áron, James B. Kadtke e Gianni Pedrizzetti. "Dynamical control for capturing vortices near bluff bodies". Physical Review E 58, n.º 2 (1 de agosto de 1998): 1883–98. http://dx.doi.org/10.1103/physreve.58.1883.

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40

Utsunomiya, H., F. Nagao, Y. Ueno e M. Noda. "Basic study of blockage effects on bluff bodies". Journal of Wind Engineering and Industrial Aerodynamics 49, n.º 1-3 (dezembro de 1993): 247–56. http://dx.doi.org/10.1016/0167-6105(93)90020-o.

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41

Cremona, Christian, e Xavier Amandolese. "Numerical Analysis of Flow Loading on Bluff Bodies". Structural Engineering International 15, n.º 4 (novembro de 2005): 252–57. http://dx.doi.org/10.2749/101686605777962955.

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Nakamura, Y. "VORTEX SHEDDING FROM BLUFF BODIES WITH SPLITTER PLATES". Journal of Fluids and Structures 10, n.º 2 (fevereiro de 1996): 147–58. http://dx.doi.org/10.1006/jfls.1996.0010.

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Dalla Longa, L., O. Evstafyeva e A. S. Morgans. "Simulations of the bi-modal wake past three-dimensional blunt bluff bodies". Journal of Fluid Mechanics 866 (18 de março de 2019): 791–809. http://dx.doi.org/10.1017/jfm.2019.92.

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The bi-modal behaviour of the turbulent flow past three-dimensional blunt bluff bodies is simulated using wall-resolved large eddy simulations. Bi-modality (also called bi-stability) is a phenomenon that occurs in the wakes of three-dimensional bluff bodies. It manifests as a random displacement of the wake between preferred off-centre locations. Two bluff bodies are considered in this work: a conventional square-back Ahmed body representative of road cars, and a simplified lorry, which is taller than it is wide, with its aspect ratio corresponding to a 15 % European lorry scale model. To our knowledge, this is the first time that the asymmetric bi-modal switching behaviour of the wake, observed experimentally, has been captured in simulations. The resulting unsteady flow fields are then analysed, revealing instantaneous topological changes in the wake experiencing bi-modal switching. The best-resolved case, the simplified lorry geometry, is then studied in greater detail using modal decomposition to gain insights into the energy content and the dominant frequencies of the wake flow structures associated with the asymmetric states. High-frequency snapshots of the switching sequence allow us to propose that large hairpin vortices are responsible for the triggering of the switching.

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Prosser, Daniel T., e Marilyn J. Smith. "Numerical characterization of three-dimensional bluff body shear layer behaviour". Journal of Fluid Mechanics 799 (21 de junho de 2016): 1–26. http://dx.doi.org/10.1017/jfm.2016.344.

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Three-dimensional bluff body aerodynamics are pertinent across a broad range of engineering disciplines. In three-dimensional bluff body flows, shear layer behaviour has a primary influence on the surface pressure distributions and, therefore, the integrated forces and moments. There currently exists a significant gap in understanding of the flow around canonical three-dimensional bluff bodies such as rectangular prisms and short circular cylinders. High-fidelity numerical experiments using a hybrid turbulence closure that resolves large eddies in separated wakes close this gap and provide new insights into the unsteady behaviour of these bodies. A time-averaging technique that captures the mean shear layer behaviours in these unsteady turbulent flows is developed, and empirical characterizations are developed for important quantities, including the shear layer reattachment distance, the separation bubble pressure, the maximum reattachment pressure, and the stagnation point location. Many of these quantities are found to exhibit a universal behaviour that varies only with the incidence angle and face shape (flat or curved) when an appropriate normalization is applied.

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Krajnović, Siniša. "Large eddy simulation of flows around ground vehicles and other bluff bodies". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, n.º 1899 (28 de julho de 2009): 2917–30. http://dx.doi.org/10.1098/rsta.2009.0021.

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A brief review of large eddy simulation (LES) applications for different bluff-body flows performed by the author and his co-workers is presented. Examples of flows range from simple cube flows characterized by sharp edge separation over a three-dimensional hill where LES relies on good near-wall resolution, to complex flows of a tall, finite cylinder that contains several flow regimes that cause different challenges to LES. The second part of the paper is devoted to flows around ground vehicles at moderate Reynolds numbers. Although the present review proves the applicability of LES for various bluff-body flows, an increase of the Reynolds number towards the operational speeds of ground vehicles requires accurate near-wall modelling for a successful LES.

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Ford, C. L., e P. M. Winroth. "On the scaling and topology of confined bluff-body flows". Journal of Fluid Mechanics 876 (13 de agosto de 2019): 1018–40. http://dx.doi.org/10.1017/jfm.2019.583.

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An experimental study of bluff bodies in confinement is presented. Two Reynolds matched rigs (pipe diameters: $D=40~\text{mm}$ and $D=194~\text{mm}$) are used to derive a picture of the flow topology of the primary-shedding mode (Kármán vortex, mode-I). Confined bluff bodies create an additional spectral mode (mode-II). This is caused by the close coupling of the shedder blockage and the wall and is unique to the confined bluff-body problem. Under certain conditions, modes-I and II can interact, resulting in a lock-on, wherein the modes cease to exist at independent frequencies. The topological effects of mode interaction are demonstrated using flow visualisation. Furthermore, the scaling of mode-II is explored. The two experimental facilities span Reynolds numbers (based on the shedder diameter, $d$) $10^{4}<Re_{d}<10^{5}$ and bulk Mach numbers $0.02<M_{b}<0.4$. Bluff bodies with a constant blockage ratio ($d/D$), forebody shape and various splitter-plate lengths ($l$) and thicknesses ($t$) are used. Results indicate that the flow topology changes substantially between short ($l<d$) and long ($l>d$) tailed geometries. Surface flow visualisation indicates that the primary vortex becomes anchored on the tail when $l\gtrsim 3h$ ($2h=d-t$). This criterion prohibits the development of such a topology for short-tailed geometries. When mode interaction occurs, which it does exclusively in long-tailed cases, the tail-anchored vortex pattern is disrupted. The onset of mode-II occurs at approximately the same Reynolds number in both rigs, although the associated dimensionless frequency is principally a function of Mach number. Accordingly, mode interaction is avoided in the larger-scale rig, due to the increased separation of the modal frequencies.

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Yao, W., e R. K. Jaiman. "Model reduction and mechanism for the vortex-induced vibrations of bluff bodies". Journal of Fluid Mechanics 827 (22 de agosto de 2017): 357–93. http://dx.doi.org/10.1017/jfm.2017.525.

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We present an effective reduced-order model (ROM) technique to couple an incompressible flow with a transversely vibrating bluff body in a state-space format. The ROM of the unsteady wake flow is based on the Navier–Stokes equations and is constructed by means of an eigensystem realization algorithm (ERA). We investigate the underlying mechanism of vortex-induced vibration (VIV) of a circular cylinder at low Reynolds number via linear stability analysis. To understand the frequency lock-in mechanism and self-sustained VIV phenomenon, a systematic analysis is performed by examining the eigenvalue trajectories of the ERA-based ROM for a range of reduced oscillation frequency $(F_{s})$, while maintaining fixed values of the Reynolds number ($Re$) and mass ratio ($m^{\ast }$). The effects of the Reynolds number $Re$, the mass ratio $m^{\ast }$ and the rounding of a square cylinder are examined to generalize the proposed ERA-based ROM for the VIV lock-in analysis. The considered cylinder configurations are a basic square with sharp corners, a circle and three intermediate rounded squares, which are created by varying a single rounding parameter. The results show that the two frequency lock-in regimes, the so-called resonance and flutter, only exist when certain conditions are satisfied, and the regimes have a strong dependence on the shape of the bluff body, the Reynolds number and the mass ratio. In addition, the frequency lock-in during VIV of a square cylinder is found to be dominated by the resonance regime, without any coupled-mode flutter at low Reynolds number. To further discern the influence of geometry on the VIV lock-in mechanism, we consider the smooth curve geometry of an ellipse and two sharp corner geometries of forward triangle and diamond-shaped bluff bodies. While the ellipse and diamond geometries exhibit the flutter and mixed resonance–flutter regimes, the forward triangle undergoes only the flutter-induced lock-in for $30\leqslant Re\leqslant 100$ at $m^{\ast }=10$. In the case of the forward triangle configuration, the ERA-based ROM accurately predicts the low-frequency galloping instability. We observe a kink in the amplitude response associated with 1:3 synchronization, whereby the forward triangular body oscillates at a single dominant frequency but the lift force has a frequency component at three times the body oscillation frequency. Finally, we present a stability phase diagram to summarize the VIV lock-in regimes of the five smooth-curve- and sharp-corner-based bluff bodies. These findings attempt to generalize our understanding of the VIV lock-in mechanism for bluff bodies at low Reynolds number. The proposed ERA-based ROM is found to be accurate, efficient and easy to use for the linear stability analysis of VIV, and it can have a profound impact on the development of control strategies for nonlinear vortex shedding and VIV.

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Ota, Terukazu, Yasunori Okamoto e Hiroyuki Yoshikawa. "A Correction Formula for Wall Effects on Unsteady Forces of Two-Dimensional Bluff Bodies". Journal of Fluids Engineering 116, n.º 3 (1 de setembro de 1994): 414–18. http://dx.doi.org/10.1115/1.2910292.

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In wind tunnel studies on the flow around bluff bodies accompanying a large separated wake, the walls of the test section severely effect the flow characteristics around them. Proposed in this paper is a correction formula for the wall effects upon two-dimensional (2-D) unsteady separated flow of incompressible fluid around bluff bodies. The proposed formula is derived from numerical results with the discrete vortex method on 2-D separated flows around an inclined flat plate, a square cylinder, and also an elliptic cylinder located between two parallel walls. It is found that the present correction formula estimates reasonably well the wall effects upon the mean and fluctuating force coefficients over a wide range of blockage ratio and angle of attack through comparing the present calculated results with numerous experimental ones by several authors.

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Gowda, B. H. Lakshmana, e V. Ganesan. "FLOW VISUALIZATION STUDIES OF CONFINED WAKES BEHIND BLUFF BODIES". Journal of Flow Visualization and Image Processing 2, n.º 4 (1995): 393–400. http://dx.doi.org/10.1615/jflowvisimageproc.v2.i4.70.

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Yang, Jing-Tang, Go-Long Tsai e Wen-Bin Wang. "Near-wake characteristics of various V-shaped bluff bodies". Journal of Propulsion and Power 10, n.º 1 (janeiro de 1994): 47–53. http://dx.doi.org/10.2514/3.23710.

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