Position details

Towards aeroacoustic simulations for liners (in relation with Safran Aircelle)
Training › Computational Fluid Dynamics - Aerodynamics

Required Education / Niveau requis

master or engineering school

From / Date de début

February to may 2013

Duration / Durée

6 months

Context / Contexte

Modern aircraft acoustic signature is nowadays a key point for design and for certification. Just look at ACARE constraints to be convinced. The global acoustic signature follows several noise sources. First, noise is emitted from the jet, but it can also come from high-lift devices or from landing gear systems.

In this context, we propose to focus attention on passive noise control taking into account liners inside nacelles. Nacelles are doors around the aircraft engine and they are built in order to assess different roles: protect the whole engine and capture acoustic sources. Acoustic “capturers” are nowadays based on liners concepts. Liners are specific material. They are composed of a perforated plate that separates the flow and small cavities under the plate. Therefore, cavities are related with external flow through small openings. Those cavities convert acoustic fluctuations into non-radiating vertical disturbances and they are designed in order to provide attenuation over a range of frequencies. Liners are nowadays installed more or less everywhere inside the nacelle. An example is proposed on Fig. 1, page 4 of the following document:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020079889_2002133431.pdf

Nowadays, designing liners is essentially empirical and the tendency is to go to a more systematic analysis using simulation in complement with engineer expertise, notably at Safran Aircelle. The goal is also to decrease the in-situ tests and pre-series.

Description / Description

Cerfacs is recognised as international specialist in numerical methods to be used in industries for many years. In particular, Cerfacs participates to the development of the elsA code of Onera (http://elsa.onera.fr) for more than 10 years. elsA is used at Safran and Airbus for the design of aircraft and turbomachinery. During the last 5 years, many efforts have been devoted to develop, implement and validate numerical components dedicated to acoustic simulations of jets. Among them, one can consider high order schemes and dedicated non-reflecting / non-radiating boundary conditions. We propose to use many of the functionalities inside elsA to perform an analysis of acoustic passive treatment like liners. We have decided to focus our attention on reproducing results obtained very recently by Zhang and Bodony (Numerical simulation of two-dimensional acoustic liners with high-speed grazing flow, Zhang and Bodony, AIAA Journal, 49(2), 365-382, 2011). We consider the 2D problem proposed in the paper. There is a laminar boundary layer located over a flat plate with a rectangular aperture towards the cavity (under the plate). The cavity represents the shape of absorbing material considered in liners. Once the flow is well established, it is proposed to add an acoustic wave near the aperture and to analyse how this wave is modified by the presence of the cavity.

During this training, we look for a student with skills on physic analysis rather than on numerical methods. The student will begin by a bibliographic analysis. Since it may not exist any lessons dedicated to this kind of problem, we look for a student with high adaptation capability. We may (or not!) ask the student to implement specific models during the training period, but the development will be well located inside the code and may not need a large time.

Finally, the student will arrive in the CFD Team of Cerfacs (about 60 persons), inside the AAM (Applied Aerodynamics and Multiphysics) group. During this period, the student will work in strong relation with Aircelle experts. An important remark showing the interest of this training perid: we have the goal to continue this training period with a PhD position (even if it is not fully sure).

Contacts / Contacts

Name: Puigt Guillaume
Phone: +33 (0)5 61 19 30 94
Fax: +33 (0)5 61 19 30 00
Email: guillaume.puigt@cerfacs.fr

Name: Boussuge Jean-François
Phone: +33 (0)5 61 19 30 62
Fax: +33 (0)5 61 19 30 00
Email: boussuge@cerfacs.fr

Salary / Rémunération

about 580 euros per month