Numerical Investigation of Unsteady Cavity Flow Aeroacoustics by Large Eddy Simulation

Year 2020, , 259 - 269, 24.01.2020

Furkan Coşgun , Sertaç Çadırcı

https://doi.org/10.21205/deufmd.2020226425

Abstract

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.

Keywords

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

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

Abstract

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.

Keywords

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

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