Titreşen diskten girdap halkası kopmalarının deneysel incelenmesi

Year 2021, Volume: 27 Issue: 4, 458 - 464, 20.08.2021

Fahrettin Gökhan Ergin

Abstract

Pah kenarlı titreşen bir diskten girdap kopmaları incelenmiştir. Deneyler yüksek hızlı bir Parçacık Görüntülemeli Hız Ölçümü (PGHÖ) sistemi kullanılarak 160 Hz görüntü toplama hızında yapılmıştır. Altı tam periyot, çevrim başına 333 hız ölçümü yapılarak ve toplamda 1999 görüntü alınarak kaydedilmiştir. Suda titreşen 175 mm çaplı diskin titreşim frekansı 0.5 Hz ve titreşim mesafesi 20 mm’dir. Rijid obje takibi ve görüntü stabilizasyon teknikleri kullanılarak disk görüntüsünü PGHÖ ham görüntülerinden çıkarabilmek için dinamik görüntü maskeleme uygulanmıştır. Burada bir koordinat değişimi söz konusudur ve bunun sayesinde disk yerinde çakılı duruyormuş gibi diskin etrafındaki akış alanı sonuçlarının incelenmesi mümkün olmuştur. Aynı zamanda istatiksel analizlerin ve faz kilitli ortalamanın kullanılması da mümkün olur. Sonuçlar her çevrimde girdap oluşumunun ve kopmasının çok düzenli ve öngörülür bir şekilde gerçekleştiğini göstermiştir. Pahlı disk kenarı geometrisinin girdap dinamiğine çok büyük etkisi vardır: Öteleme pahlı tarafa olduğunda diğer düz tarafta büyük ve yapışık bir girdap oluşurken, ötelemenin yönü değişip düz tarafa doğru olduğunda daha önce oluşan büyük ve yapışık girdap merkezden uzaklaşarak kopmuş ve yatay eksene göre 45° eğimi olan bir kayma tabakası gözlemlenmiştir. Bu da asimetrik disk kenarı geometrisinin tüm çevrimde net bir kuvvet oluşturduğu anlamına gelir.

Keywords

Girdap kopması, Titreşen disk, Parçacık görüntülemeli hız ölçümü, Dinamik maskeleme, Obje takibi, Görüntü stabilizasyonu

Experimental investigation of vortex ring shedding from oscillating disc

Abstract

Vortex shedding from an oscillating disc with a chamfered tip is investigated. The experiments are performed using a high-speed Particle Image Velocimetry (PIV) system with 160 Hz frame acquisition frequency. Six full cycles are recorded with a total of 1999 recordings, i.e. 333 velocity measurements resolving a single cycle. The 175-mm-diameter disc oscillation frequency was 0.5 Hz within a 20 mm displacement in water. Dynamic image masking is performed to remove the disc shape from the PIV raw images, using rigid object tracking and image stabilization techniques. This implies a coordinate transformation and allows the investigation of flow field results with respect to the disc, as if it were stationary. This allows the use of statistical analysis and phase-locked averaging. The results indicate that the vortex formation and shedding from-cycle-to-cycle is very stable and predictable. The chamfered disc tip geometry has great influence in the vortex dynamics: When the motion is towards the chamfered side, a big, attached trailing vortex is present on the flat side; and when the motion is reversed towards the flat side the big trailing vortex is shed off outwards from the center, and a shear layer with a 45° orientation is formed. This means the asymmetric disc tip geometry generates a net force for the complete cycle.

Keywords

Vortex shedding, Oscillating disc, Particle image velocimetry, Dynamic masking, Object tracking, Image stabilization

References

• [1] Zhang Y, Sarkar P, Hu H. “An experimental study of microburst-wind loads on gable-roofed building models”. 42nd AIAA Fluid Dynamics Conference and Exhibit, New Orleans, Louisiana, 25-28 June 2012.
• [2] Glasstone S, Dolan PJ. The Effects of Nuclear Weapons, 3rd ed. Washington, USA. US Department of Defense and US Department of Energy, 1977.
• [3] McCowan B, Marino L, Vance E, Walke L, Reiss D. “Bubble ring play of bottlenose dolphins (Tursiops truncatus): Implications for cognition”. Jourbal of Comparative Psychology, 114(1), 98-106, 2000.
• [4] Gemmell BJ, Colin SP, Costello JH, Sutherland KR. “A ctenophore (comb jelly) employs vortex rebound dynamics and outperforms other gelatinous swimmers”. Royal Society Open Science, 2019. Doi:10.1098/rsos.181615.
• [5] Kristensen LD, Sparrevohn CR, Christensen JT, Støttrup JG. “Cryptic Behaviour of Juvenile Turbot Psetta maxima L. and European Flounder Platichthys flesus L”. Open Journal of Marine Science, 4(3), 185-193, 2014.
• [6] Sauret A, Morize C, Gondret P. “Erosion of a granular bed by an oscillating foil”. 68th Annual Meeting of the APS Division of Fluid Dynamics, Boston, Massachusetts, 22-24 November 2015.
• [7] Hu Y, Shi L, Parameswaran S, Smirnov S, He Z. “Left ventricular vortex under mitral valve edge-to-edge repair”. Cardiovascular Engineering Technology, 1(4), 235-243, 2010.
• [8] Töger J, Kanski M, Carlsson M, Kovács SJ, Söderlind G, Arheden H, Heiberg E. “Vortex ring formation in the left ventricle of the heart: analysis by 4D flow MRI and Lagrangian coherent structures”. Annals of Biomedical Engineering, 40(12), 2652-2662, 2012.
• [9] Cler D. “CFD Application to Gun muzzle blast-a validation case study”. 41st Aerospace Sciences Meeting and Exhibit, Reno, Nevada, 6-9 January 2003.
• [10] Lucey GK. Vortex Ring Generator: Mechanical Engineering Design for 100-Kpsi Operating Pressures. Adelphi, Maryland, Army Research Laboratory 2000.
• [11] Arakeri JH, Das D, Krothapalli A, Lourenco L. “Vortex ring formation at the open end of a shock tube: a particle image velocimetry study”. Physics of Fluids, 16(4), 1008-1019, 2004.
• [12] Eschricht D, Panek L, Yan J, Michel U, Thiele F. “Jet noise prediction of a serrated nozzle”. 14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference), Vancouver, British Columbia, Canada, 5-7 May 2008.
• [13] Leishman JG, Bhagwat MJ, Ananthan S. “The vortex ring state as a spatially and temporally developing wake instability”. Journal of American Helicopter Society, 49(2), 160-175, 2004.
• [14] Ergin FG. “Measurements of micro-mushroom patterns in a magnetic micromixer”. 5th Micro and Nano Flows Conference, Milan, Italy, 11-14 September 2016.
• [15] Shariff K, Leonard A. “Vortex rings”. Annual Review of Fluid Mechanics, 24(1), 235-279, 1992.
• [16] Fuchiwaki M, Kuroki T, Tanaka K, Tababa T. “Dynamic behavior of the vortex ring formed on a butterfly wing”. Experiments in Fluids, 2013. Doi: 10.1007/s00348-012-1450-x.
• [17] Karakaş F, Paça O, Köse C, Son O, Zaloglu B, Fenercioğlu İ, Cetiner O. “Çırpan kanatta kanat profilinin etkisi”. Journal of Aeronautics and Space Technology (Havacilik ve Uzay Teknolojisi Dergisi), 7(2), 1-16, 2014.
• [18] Kurtulus DF, David L, Farcy A, Alemdaroglu N. “Aerodynamic characteristics of flapping motion in hover”. Experiments in Fluids, 44(1), 23-36, 2007.
• [19] Wu X, Hu Y, Li Y, et al. “Foundations of offshore wind turbines: A review”. Renewable and Sustainable Energy Reviews, 104, 379-393, 2019.
• [20] Thiagarajan KP, Troesch AW. “On the use of various contour shapes for evaluating circulation from PIV data”. Thirteenth Australasian Fluid Mechanics Conference, Melbourne, Australia, 13-18 December 1998.
• [21] Lake M, He H, Troesch AW, Perlin M, Thiagarajan KP. “Hydrodynamic coefficient estimation for TLP and spar structures”. Journal of Offshore Mechanics and Arctic Engineering, 122(2), 118-124, 2000.
• [22] Sireta F-X, Thiagarajan KP, Molin B, Pistani F. “Hydrodynamic coefficients of porous plates and application to subsea deployment”. Marine Operations Specialty Symposium, Singapore, 5-7 March 2008. [23] Wadhwa H. “Hydrodynamics of Porous Plates and İnfluence of Free Surface Proximity”. Dissertation, The University of Western Australia, Perth, Avustralya, 2011.
• [24] Ergin FG. “Dynamic masking techniques for particle ımage velocimetry”. Isi Bilim ve Teknigi Dergisi, 37(2), 61-74, 2017.
• [25] Ergin FG, Olofsson J, Watz BB, Gade-nielsen NF. “Dynamic masking application examples in two-phase flow pıv measurements”. 19th International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics, Lisbon, Portugal, 16-19 July 2018.
• [26] Ergin FG, Watz BB, Wadhwa N. “Pixel-accurate dynamic masking and flow measurements around small breaststroke-swimmers using long-distance MicroPIV”. 11th International Symposium on Particle Image Velocimetry, Santa Barbara, California, 14-16 September 2015.
• [27] Ergin F, Watz B, Gade-Nielsen N. “A Review of planar PIV systems and image processing tools for lab-on-chip microfluidics”. Sensors, doi: 10.3390/s18093090, 2018.
• [28] Dantec Dynamics. “DynamicStudio 6.4 release with new Dynamic Masking add-on”. https://www.dantecdynamics.com/news/dynamicstudio-6-4-release-with-new-dynamic-masking-add-on (04.11.2018).
• [29] Ergin FG. “PIV accuracy improvement near stationary walls using interrogation window masking”. 12th International Symposium on Particle Image Velocimetry, Pusan, Korea, 19-21 June 2017.
• [30] Westerweel J, Scarano F. “Universal outlier detection for PIV data”. Experiments in Fluids, 39(6), 1096-1100, 2005.
• [31] Ergin FG, Watz BB, Erglis K, Cěbers A. “Time-resolved velocity measurements in a magnetic micromixer”. Experimental Thermal and Fluid Science, 67, 6-13, 2015.