Numerical Investigation of Unsteady Cavity Flow Aeroacoustics by Large Eddy Simulation

Öz

Flow along a cavity is of special interest for researchers due to the occurrence of free shear layer flow and related high levels of sound and pressure forces. In this study, turbulent flow along an open cavity at a low inlet Mach number (Ma = 0.034) is modelled by Large Eddy Simulations (LES). The velocity profiles at various stations inside the open cavity are compared to available experimental data.  It is found that LES results agree with experimental data and detects the transient pressure change in the flow field satisfactorily. Transient pressure data in the flow field is evaluated in acoustic analogy. The noise generated by the cavity is compared with the established Rossiter modes and is found to be reasonable.  To create an effect on the sound pressure levels (SPL), a small obstacle with quadrilateral cross section is immersed in the shear layer at three different locations. This causes that the SPL peaks are reduced compared to the case without any obstacle.  Thus, cavity-induced noise form specific frequencies are redistributed to high frequency broadband noise as a result of this passive flow control method.

Anahtar Kelimeler

• Low Mach number flow,Passive flow control,Acoustic analogy,Rossiter mechanism

Zamana Bağlı Kavite Akışı Aeroakustiğinin Büyük Girdap Simülasyonu ile Sayısal Olarak İncelenmesi

Öz

Bir kavite boyunca akış, serbest kayma tabakası akışının oluşması ve buna bağlı olarak yüksek seviyelerde ses ve basınç kuvvetleri nedeniyle araştırmacılar için özel bir ilgi alanı oluşturmaktadır. Bu çalışmada, düşük Mach sayısındaki (Ma = 0.034) açık bir kavite boyunca türbülanslı akış Büyük Girdap Simülasyonları (LES) ile modellenmiştir. Açık kavite içindeki çeşitli konumlardaki hız profilleri, mevcut deneysel verilerle karşılaştırılmıştır. LES sonuçlarının deneysel verilerle uyuştuğu ve akış alanındaki zamana bağlı basınç çalkantılarını tatmin edici şekilde tespit edebildiği bulunmuştur. Akış alanındaki bu basınç verileri akustik analojide değerlendirilmiştir. Kavitenin ürettiği gürültü, Rossiter modlarıyla karşılaştırılmış ve makul seviyede bulunmuştur. Ses basıncı seviyeleri (SPL) üzerinde bir etki yaratmak için, kesme katmanına üç farklı noktada dörtgen kesitli küçük bir engel daldırılmıştır. Bu, herhangi bir engel olmadığı duruma kıyasla SPL doruklarının azalmasına neden olmaktadır. Bu nedenle, kavite kaynaklı gürültüye özgü frekanslar, bu pasif akış kontrol yönteminin bir sonucu olarak yüksek frekanslı geniş bant gürültüsüne yeniden dağıtılır.

Anahtar Kelimeler

• Düşük Mach sayısı akışı,Pasif akış kontrolü,Akustik analoji,Rossiter mekanizması

Kaynakça

1. L.N. Cattafesta, Q. Song, D.R. Williams, C.W. Rowley, and F.S. Alvi, " Active control of flow-induced cavity oscillations, Progress in Aerospace Sciences", Vol. 44, pp. 479–502, 2008.
2. F., Cosgun, Aeroacoustics Investigation of Low Mach Number Cavity Flow, Istanbul Technical University, MSc Thesis, Istanbul, 2018.
3. S.D. Crook, T.C.W. Lau, and R.M. Kelso, Three-dimensional flow within shallow, narrow cavities”, Journal of Fluid Mechanics, Vol. 735, pp. 587–612, 2013.
4. N. Curle, “The influence of solid boundaries upon aerodynamic sound”, Philosophical Transactions of the Royal Society of London.Series A, Mathematical and Physical Sciences, Vol. 231, pp.505-514, 1955.
5. L.F. East, “Aerodynamically induced resonance in rectangular cavities”, Journal of Sound and Vibration, Vol. 3, pp. 277–287, 1966.
6. J.E. Ffowcs Williams and D. Hawkings,“Sound generation by turbulence and surfacesin arbitrary motion”, Philosophical Transactionsof the Royal Society of London. SeriesA, Mathematical and Physical Sciences, Vol. 264,pp. 321–342, 1969.
7. H.H. Heller and D.B. Bliss, “The Physical mechanism of flow-induced pressure fluctuations in cavities and concepts for their suppression”, AIAA 2nd Aero-Acoustics Conference, Hampton, USA, 1975.
8. L. Larchevêque, P. Sagaut and P. Comte,“Large-eddy simulation of a compressible flow in a three-dimensional open cavity at high Reynolds number”, Journal of Fluid Mechanics, Vol. 516, pp. 265–301, 2004.

9. G. Li, Numerical Simulation of Environmental Flow over Buildings for Renewable Energy Application, MSc Thesis, Arizona State University, Arizona, USA, 2015.
10. M.J. Lighthill, “On sound generated aerodynamically I. General Theory”,Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 211, pp. 564-587, 1951.
11. L.V. Lopes, A New Approach to Complete Aircraft Landing Gear Noise Prediction, PhD Thesis, The Pennsylvania State University, Pennsylvania, USA, 2009.
12. L.V. Lopes, “Prediction of landing gear Noise reduction and comparison to measurements”, 16th AIAA/CEAS Aeroacoustics Conference, Hampton, USA, 2010.
13. [13] T. Nouzawa, Y. Li, N. Kasaki, and T. Nakamura, “Mechanism of aerodynamic noise generated from front-pillar and door mirror of automobile”, Journal of Environment and Engineering, Vol. 6, pp. 615–626, 2011.
14. E. Ozsoy, Numerical Simulation of Incompressible Flow Over Three-Dimensional Rectangular Cavity, PhD Thesis, IstanbulTechnical University, Istanbul, Turkey, 2010.
15. J. Rossiter, “Wind-tunnel experiments on the flow over rectangular cavities at subsonic and transonic speeds”, Aeronautical Research Council Reports and Memoranda, London,England, 1966.
16. V. Sarohia and P.F. Massier, “Control of cavity noise”, Journal of Aircraft, Vol. 14, pp. 833–837, 1977.
17. L.L. Shaw, “Suppression of aerodynamically induced cavity pressure oscillations”, The Journal of the Acoustical Society of America 66, 880, 1979.
18. S. Yamouni, C. Mettot, D. Sipp and L.Jacquin, “Passive control of cavity flows”, Journal of Aerospace Lab, Issue 6, 2013.
19. B. Zafer and F. Cosgun, “Aeroacoustics investigation of incompressible unsteady cavity flow”, Journal of The Faculty of Engineering and Architecture of Gazi University, Vol. 31-3, pp. 665–675, 2016.
20. Fluent Theory Guide, Ansys Inc, 2013.
21. B. Zafer and F. Cosgun, “Aeroacoustics analysis of cavity flow” Journal of Thermal Science and Technology, Vol. 38-2, pp 25-38, 2018.
22. B. Zafer and O. Konan, “Aeroacoustic analysis of cavity – airfoil Interaction”, DokuzEylul University-Faculty of Engineering Journal of Science and Engineering, Vol. 19, Issue 55,January 2017.
23. V. G. Basovsky, I. M. Gorban, O.V.Khomenko, “Modification of hydrodynamic and acoustic fields generated by a cavity with fluid suction”, Modern Mathematics and Mechanics, Chapter 9, pp 137-158, 2018.