DAEP Seminars 2019

Study of a singular component of the jet noise: the screech

• Monday 25 November 2019 - 11:00 am - room 38.137 - by Bertrand Mercier (TU DELFT)

Jet noise is a major subject of study in aeroacoustics, with its main applications in the aeronautics and space fields. Indeed, jet noise dominates the nuisance perceived by local residents during the take-off phase of aircraft, and remains a significant source of noise during the climb. This noise is attributed to the radiation of turbulent structures present in the jet’s shear layer. Due to the nature of these sources, the acoustic spectrum of jet noise is broadband.

Beyond this, when the jet is supersonic and not ideally relaxed, a very high intensity tonal component dominates the initially wideband signature of the jet noise under certain conditions. This phenomenon, which still raises questions, is called the “screech”, a name that refers to the particularly shrill noise associated with it.

In this seminar, we will propose an analysis of the mechanisms involved in the generation of screech. This study is mainly based on several test campaigns, which involved acoustic and aerodynamic measurements in the LMFA anechoic wind tunnel.

Studies of deformable flapping wings for lift flight

• Friday, November 22, 2019 - 11:00 a.m. - room 38.137 - by Daniel Diaz-Arriba

The study is done at ISAE-Supaero in collaboration with the Pprime Institute in Poitiers. Experimental tests of optical measurements (PIV) on flexible flapping wings have been carried out in the facilities set up for several years already at the Pprime Institute on the subject of flapping wings. In addition, non-intrusive methods of force determination were analyzed. Subsequently, simulations (STAR-CCM+) are conducted in order to analyze the physics of the flow generated by rigid and flexible flapping wings and to start an optimization process of the aerodynamic performances. Finally, the best performing conditions will be tested experimentally to verify the results.

New challenges of a disruptive propulsion system: towards an evolution of design and analysis methods

• Friday, October 18, 2019 - 11:00 a.m. - room 38.137 - by Emmanuel Benichou

With the aim of drastically reducing fuel consumption, aircraft design in general and the propulsion cell in particular require a global review of design methods due to ever more advanced integration. Thus, engine manufacturers need to have at their disposal, as early as possible in the design process, decision support methodologies that are as close as possible to the physical reality imposed by the interdependence of a majority of aircraft systems, of which the propulsion cell is most often the focal point.

Feedback on the M2 internship of two research students

• Thursday, October 10, 2019 - 2:00 pm - room 38.137 - by Julien Sablon and Charles Thoulon

Julien Sablon and Charles Thoulon, research students at DAEP, present the work done during their M2 internship. Julien worked on stratified flows around a cylinder at the École polytechnique fédérale de Lausanne with François Gallaire, while Charles worked on real gas nozzle flows at Imperial College with Émile Touber.

Modeling compressor operation during a pumping cycle

• Friday, June 21, 2019 - 11:00 am - room 38.137 - by Ludovic Rojda

A gas turbine is a machine that provides energy to the gas flowing through it. The flows within the various components of a gas turbine are complex since they are intrinsically turbulent and unsteady. In compressors, one of the particularities is that the direction of the flow opposes that of the pressure gradient, so that the pressure forces oppose the inertia forces. At high compression ratios, the aerodynamic stability of the flow is precarious and only a slight aerodynamic disturbance is required to initiate an instability of the operating regime such as surging, which is critical for operability.

This phenomenon being systemic, the aim of this thesis is to model a high pressure compressor within its test bench environment during the instability occurrence. This type of modeling aims to allow a relevant consideration of the influence of the elements upstream and downstream of the compressor in order to answer this question:

“What is the impact of Engine components on the operation of the near-pumping compressor and what is the most efficient computational strategy to simulate the pumping phenomenon and predict its impact on the vibratory behavior of gas turbine blades?”

The pumping phenomenon being mainly longitudinal, the proposed approach uses a three-dimensional numerical resolution of the flow in the compressor and a one-dimensional resolution of the flow in the rest of the system. The methodology is then oriented towards an unsteady coupling of a 3D RANS CFD code (elsA) and a 0D/1D gas turbine performance code (PROOSIS - Fluidapro) in order to simulate a compressor pumping cycle in an installed environment. This approach allows a significant reduction of the computational cost compared to an unsteady three-dimensional simulation of the whole system.

Finally, the low-frequency, high-amplitude oscillations that affect the system generate mechanical vibrations capable of destroying the compressor and then the gas turbine as a whole. It is therefore easy to understand why it is so important to predict the onset and development of surge.

Experimental and numerical study of the transonic dither on a diedric profile - application to the case of a supersonic launcher

• Friday, May 24, 2019 - 11:00 am - room 38.137 - by Jéromine Dumon

Modeling of propeller-wing interaction for convertible UAV

• Friday, March 29, 2019 - 11:00 a.m. - room 38.137 - by Yuchen Leng(Presentation)

In the context of convertible UAV design, the aerodynamic forces induced by the propeller wake strongly affect the mechanics of low speed flight. The seminar will present the work done at DAEP: propeller and wake modelling, and the coupling of the MachUp library-based lift line model.

Aerodynamic analysis by exergy method

• Friday, February 15, 2019 - 11:00 a.m. - room 38.137 - by Miguel Aguirre

The exergy method is a powerful aerodynamic evaluation technique based on the application of the 2nd principle of thermodynamics. Used in the field of propulsion since the 1970s, its use has recently been extended to external aerodynamics in order to analyze innovative aircraft configurations. The aim of this seminar is to present this method and its recent applications. In addition, the work on the field carried out within DAEP during 2018 will also be presented, namely: development of the Epsilon code (post-processing of CFD simulations by the exergy method) and various research works on airfoils and wings.