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UID:0-274@aerospace.technion.ac.il

DTSTART;TZID=Asia/Jerusalem:20201207T123000

DTEND;TZID=Asia/Jerusalem:20201207T133000

DTSTAMP:20230525T065216Z

URL:https://aerospace.technion.ac.il/events/a-direct-numerical-simulation-
 on-aerofoil-noise-due-to-flow-separation-and-stall/

SUMMARY:A Direct Numerical Simulation on Aerofoil Noise due to Flow Separat
 ion and Stall
DESCRIPTION:Lecturer:Associate Professor Jae-Wook Kim\n Faculty:Engineering
  and Physical Sciences\n Institute:University of Southampton\n Location:ht
 tps://technion.zoom.us/j/8996991299\n Zoom: \n Abstract: \n Details: \n Ae
 rofoil self-noise produced by flow separation and stall is relatively litt
 le understood regarding the underlying generation mechanisms. The focus of
  this talk is to provide an improved level of understanding particularly w
 ith regard to the dipole noise sources utilising a high-fidelity direct nu
 merical simulation. A NACA0012 aerofoil is considered under three differen
 t flow conditions at a Reynolds number of 50\,000 and a Mach number of 0.4
 .  These include: a pre-stall condition with a laminar separation bubble\
 , near-stall and fully stalled. The noise radiation in the far-field is si
 gnificantly increased at low frequencies for the full-stall case for all o
 bserver directions which is consistent with previous experimental observat
 ions. The dominant source regions for each configuration are identified fo
 r low\, medium and high frequencies\, separately. A number of key findings
  are made concerning the source characteristics in full-stall which differ
  considerably from the lower angle of attack cases. It is found that the l
 ocation of the dominant sources changes more significantly with frequency 
 for the full-stall case. Additionally\, for medium to high frequencies the
  maximum acoustic source amplitude is weaker for the full-stall case\, des
 pite comparable levels observed in the far-field. This seemingly contradic
 tory observation highlights the importance of phase variations in the wall
  pressure fluctuations. For the frequencies considered in this work it is 
 shown that the\nfull-stall case usually produces a relatively more in-phas
 e source distribution\, resulting in a more efficient radiation despite th
 e lower amplitude levels. The important flow structures which are responsi
 ble for the dipole sources are also identified through analysis of the pre
 ssure field at isolated frequencies. It is found that for low frequencies 
 coherent structures in the shear layer are responsible for the scattering 
 of the wall pressure fluctuations at the TE\, which agrees with previous f
 indings in the literature. However\, at medium and high frequencies the sh
 ear layer structures are found to be relatively weak in the proximity of t
 he TE. This indicates that the noise may be generated through other means\
 , for example scattering of fluctuating pressure induced by vortices shed 
 from the TE.\nJoin the Zoom meeting
CATEGORIES:Seminars
LOCATION:https://technion.zoom.us/j/8996991299

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