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Job Record #15668
TitleStudy of laminar / turbulent transition over swept oscillating
CategoryPhD Studentship
EmployerONERA
LocationFrance, PARIS
InternationalYes, international applications are welcome
Closure DateMonday, June 10, 2019
Description:
ONLY APPLICATIONS FROM CITIZENS OF THE EUROPEAN UNION WILL BE CONSIDERED
(FUNDING IS LIMITED TO THOSE STUDENTS)

Reducing the consumption of an aircraft promotes the use of laminar wings with
large aspect ratio. A large aspect ratio reduces the induced drag while a
so-called laminar profile allows the development of a laminar boundary layer
over a large part of the wing, thus reducing friction drag. However, a wing with
large aspect ratio is by nature flexible and therefore exhibits large stationary
and unsteady deformations under aerodynamic loads. Fundamental laminar /
turbulent transition mechanisms are well known for boundary layers developing on
fixed profiles. The Tollmien-Schlichting and Cross-Flow instabilities are
generally responsible for this transition on a cruising plane. For profiles
exhibiting a periodic oscillation movement (flexible wing), knowledge about
these transition mechanisms is lacking. The works of Desopper (1977) and more
recently of Studer (2005) have experimentally characterized the transition of
oscillating boundary layers developing on flat plates. Local stability analyzes
(Studer 2005) based on quasi-steady hypotheses were also carried out and showed
their predictive limit when the propagation time of the Tollmien-Schlichting
waves is comparable to the time of oscillation of the boundary layer. Not only
are the transition mechanisms for oscillating wings poorly known, but to our
knowledge there is no theoretical approach to generally address these
oscillatory boundary layer transition problems. The methodological objective of
this thesis is to develop such approaches in order to determine / analyze the
instabilities developing on oscillating boundary layers (with or without sweep)
for any frequency oscillatiton and amplitude of the oscillating motion. This
work will be based on recent methodological and numerical developments at the
Department of Aerodynamics, Aeroelasticity and Acoustics (DAAA) concerning the
determination of periodic solutions (stabilization techniques, harmonic balance
methods) and their stability by Floquet analyzes. The candidate will have to
extend to periodic flows the well-known resolvent analyzes for stationary flows.
At the beginning of the thesis, these approaches will be conducted on academic
configurations to accurately calculate periodic solutions. Then, these analyzes
will be extended to more realistic configurations of laminar wings with
different sweep angles. In this case, three-dimensional numerical LES / DNS
simulations will be performed. The stability analyzes will then be performed on
periodic components (phase averages) extracted from these simulations and
compared to the experimental results available at ONERA. Moreover, the validity
of the classical (quasi-steady) approach of the RANS transition criteria will be
evaluated.
Contact Information:
Please mention the CFD Jobs Database, record #15668 when responding to this ad.
NameSIPP DENIS
Emaildenis.sipp@onera.fr
Email ApplicationYes
URLhttps://w3.onera.fr/formationparlarecherche/sites/w3.onera.fr.formationparlarecherche/files/mfe-daaa-2019-11.pdf
AddressONERA
8 RUE DES VERTUGADINS
92190 MEUDON
Record Data:
Last Modified09:17:59, Tuesday, February 19, 2019

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