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

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.

Numerical Investigation of Unsteady Cavity Flow Aeroacoustics by Large Eddy Simulation

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.

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Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi-Cover
  • ISSN: 1302-9304
  • Yayın Aralığı: Yılda 3 Sayı
  • Başlangıç: 1999
  • Yayıncı: Dokuz Eylül Üniversitesi Mühendislik Fakültesi