In this research, we will investigate and develop applications of multistable composite panels and shells as morphing surfaces capable of large shape changes under external loading and embedded actuation. This research topic implies the study of complex non linear phenomena that take place during large displacements of slender structures (beams, arches, plates or shells) in order to develop models and tools for the prediction, design and control of such phenomena. Large non linearities are the fundamental keys to understand stability or loss of stability of slender structures, both in the static and dynamic domains. Our aim is to tackle two relevant subjects in the very large domain of non linear structural behaviour, which will represent the two main axes of the present research project: i. a first goal is to develop an integrated theoretical and numerical approach to design composite laminates which may hold several equilibrium configurations, exploiting the effects of geometric non-linearities, anisotropy, and pre-stresses induced by the through-the-thickness variation of the material properties. The idea is to start from reasonably simple analytical models for the study of complex non linearities, in order to capture the fundamental phenomena involved, and to validate the captured trends through numerical and experimental tools. These results will open the way to the modelling, design and optimisation of more complex multistable structures; ii. a second aspect is the theoretical study and experimental test of the use of embedded active materials, such as Shape Memory Alloys (SMA) wires/stripes, to control the shape of the structure without the need for joints or conventional actuators. Synthetically, our topic is the modelling, optimal design and shape control of slender multistable structures, i.e. structures that can hold several equilibrium positions without the application of external forces. Domains of application are quite wide and they stand at the border of very innovative and recent research topics: such structures are present in Nature, but also are constitutive parts of modern devices, such as morphing or deployable structures for aeronautical and aerospace applications, mirrors, thin screens, and so on. The developments proposed in our project embrace several aspects: modelling, numerical and experimental validation, optimal design of non linear slender structures. Considering the field of application and the envisaged research, the present project can be evaluated in the framework of the FRAE-ANR protocol (strong links to themes I, VI, VIII, IX; also possible link to theme III). This project aims at gathering a group of young scientists who are experts in different fields of structural mechanics (modelling, optimisation and design, elasticity, smart materials, singularity formation, stability, damage,…) in order to build up and consolidate a research team based at Institut Jean Le Rond d’Alembert (IJLRdA), Université Pierre et Marie Curie (UPMC) with external collaborations from Ecole Nationale Supérieure de Cachan and Università Roma 1 La Sapienza. This project will also enhance exchanges among the different fields of structural mechanics which are the background of the team members. Indeed, this project will be also an opportunity to give a contribution to the nascent experimental activity at IJLRdA by the development of simple experimental setups. This experimental activity was initiated few years ago (in the field of fluid mechanics) and it is highly encouraged by the direction of the institute IJLRdA and CNRS.

In the recent years armored materials have been intensively developed for various applications. The renaissance of gerrilla groups in several international and national conflicts around the world has increased the number of incidents involving light weapons. These weapons are increasingly harmful, now being able to perforate the armored vehicles and aircrafts that were secure before and making compulsory to reinforce the resistance of the materials used. In addition, there is an interest in increasing the action area of these vehicles being exposed to more severe conditions. The design of armored materials must find a compromise between performance and weight. This can only be achieved investing into new research lines focusing on the development of new materials with significant added value. Recent advances on the performance of armored materials have been based on materials able to quickly dissipate most of the kinetic energy generated during the impact of the projectile on the armored plate. For instance, ceramic materials have shown a good balance between weight and the amount of energy dissipated during the fracture process. Composite materials present similar densities and energy dissipation rates by resorting to the delamination process. Finally, porous materials can be even lighter being the process of compaction the main responsible for the energy dissipation. One energy dissipation process that remains still unexplored is the process of cavitation. The project CACHMAP (Laser shock induced cavitation in porous matrices) is a fundamental research project aiming at quantifying the total amount of energy dissipated by cavitation when a light solid porous matrix saturated with a liquid is exposed to short pressure pulses. Because this project proposes the development of new technologies to protect citizens against ballistic aggressions, it fits into the EU societal challenge “Secure societies- Protecting freedom and security of Europe and its citizens”. The project is proposed for a total duration of 3 years and it is based on the experimental characterization of various porous matrix saturated with various liquids. The use of shock waves induced by short laser pulses will allow characterizing micron size porous material samples with sizes in the range of few millimeters thickness and with surfaces of the order of square centimeters. The project will concentrate on the implementation and development of the experimental techniques required to characterize the processes. In a first stage, polymeric piezoelectric pressure sensors will be used to capture the averaged response of the material to shock waves which is expected to be influenced by the inception of cavitation. This technology will be further developed in order to filter out specific range of frequencies adapted to laser pulses. State of the art data treatment methods will be also explored in order to maximize the amount of information extracted from the experimental signals. Finally, the project will also include the development of models capable to predict the response of dry and saturated porous matrices which may be eventually used for future designs of new armored materials.

Electrical power generation is one of the major issues in the context of economic developments and eco-responsible policy. By 2020 for solar, wind and gas turbines (GTs) fuel types by the Californian Independent System Operator (CalISO). The load ramps highlighted by the black arrows in the early morning and in the evening are expected to be of the order of +8.103MW, -6.3.103MW and +13.5.103MW, respectively. These loads would need to be generated or absorbed (GT shut down) within a range of two hours each. According to the US Department of Energy, by 2040, natural gas (for GTs) and renewables would be the two first fuel types for electricity generation. Both natural gas and renewables would see their contribution in electrical power generation increase by 15 and 30%, respectively. The other actual resources (nuclear, coal, liquids) would see their contribution decrease. Therefore, in order to fulfill the electrical power demand, especially when it comes to face with the energy supply fluctuations inherent to renewable energy sources, gas turbines provide a reliable solution. However, a large variability in their operating conditions leads to a high level of pollutant emissions and high risks of damage. Diluted regime combustion (e.g. MILD - Moderate or Intense Low oxygen Dilution) appears to be an auspicious process for gas turbines to ensure low emission levels over a wide range of operating conditions. In this regime, fuel is mixed with a highly diluted and heated air to create a spatially distributed reaction zone with a reduced peak temperature. COnfined COunterflow Reactors (CO²Res) were design with the aim to provide the most suitable flow features favorable to the MILD combustion. Therefore, they can be viewed as the ideal benchmark to research studies devoted to bring the technological breakthrough needed to: i) improve the efficiency and; ii) reduce pollutants emissions in MILD combustion applications. To optimize MILD combustion, fast and efficient mixing of reactants with exhaust gases is mandatory. The latter is not only a technical issue, but the lack of theoretical knowledge on turbulent mixing in such flow configurations is clearly pointed out (Kruse et al. 2015). This combustion regime is a priori characterized by a competition between the mixing and chemistry time-scales with a strong influence of the differential diffusion effects (Christo and Dally, 2005, Cavaliere and de Joannon 2004). It thus drastically differs from the conventional jet flames for which mathematical models generally account for fast chemistry and negligible differential diffusion effects. This project aims at bringing concrete elements of fundamental research to understand, model and predict the turbulent active-scalar mixing, in the context of MILD combustion. Such mixing does couple back on the flow dynamics. As a consequence, a correct accounting of mixing is even required to describe the flow dynamics. The multi-disciplinary consortium composed of 4 young researchers, 1 post-doc and 1 senior Professor has proven its experimental, numerical and theoretical expertise in the analysis of turbulent mixing. We therefore aim at performing analytical developments as well as experimental approaches and numerical simulations of a simplified academic based MILD combustor. The project will be divided in three interconnected blocs: i) Turbulent mixing; ii) Turbulent/Non-Turbulent interface and iii) Turbulent modelling. A full description of the phenomenology of the turbulent active-scalar mixing in CO²Res will be provided. Finally, models for CO²Res based on joint experimental, numerical and analytical developments will be proposed in order to perform reliable predictive simulations.

The S2MF project intends to overcome a scientific and technological barrier in the field of underwater acoustical imaging. The project aims at improving the tools used for imaging the seafloor, and measuring backscattered indexes. The leading idea is to combine the concept of saturated multi-frequency transmission with innovative wideband receiving sensors. At transmit, the harmonic components are created by taking advantage of the nonlinear propagation in water: the transmitter is driven at a single fundamental frequency, and delivers a large acoustic power; the initial sine wave distorts along propagation into a saw tooth shape. Hence, a unique source generates harmonics beams that are perfectly correlated. It enables in turn to produce – at several frequencies – sets of images that are perfectly correlated, both in time and in space. Systems based on such a multi-frequency concept are foreseen to be an asset in many applications (e.g., characterization of the seafloor, of fish schools…). For example because of the frequency dependence of the beam penetration, it is likely that an imaging system could detect artifacts such as oil slicks, or buried objects. The S2MF project focuses on the technological locks implied by the required wide-band receiving sensors. As a proof of concept, two prototypes of multifrequency systems will be conceived and operated: a sounder and a side-scan sonar. Partners of this project are the Institut d’Alembert (UPMC), ENSTA Bretagne and Ifremer.

The NumERICCS project aims at coordinating the efforts of the University/CNRS research groups of ENSAM-Lille, ECLille and UPMC, of the french aerospace research organization ONERA, and of the french aircraft-engine manufacturer SNECMA, towards the control of the destructive surge instability observed at the high-load limit of modern axial-flow compressors. This is a combined experimental and numerical work, whose expected outcome is the design, numerical simulation and experimental assessment of an original compressor-surge control device, using nonsynthetic (net massflow injection) jets ahead of the blades' leading-edge. The 48-month project will address multiple technological challenges to achieve this goal. New experimental data, both with and without flow-control, will be acquired in 2 existing experimental set-ups which will be specifically modified during the project to insert the actuators designed to control the flow: (1) a SNECMA-designed compressor-stage on the BERAC test-rig at ENSAM-Lille (LML) which will provide detailed aerodynamic data of rotating-stall and surge inception; several LML-patented (ECLille) actuators will be placed circumferentially, near the rotor's leading-edge, and optimized experimentally (massflow, frequency, phase, duty-cycle; LML) and computationally (distance from leading-edge, injection angle; ONERA); detailed measurements of the optimally-controlled flow will then be performed, and compared with full-stage RANS (with deterministic unsteadiness) CFD (ONERA). (2) a generic nonrotating wind-tunnel set-up of an isolated cantilever blade with tip-clearance at ONERA-Meudon which allows for adjustment of several flow (tip-clearance height, flow-incidence, incoming boundary-layer thickness) and control (location, injection angle, massflow, frequency) parameters, to study their effects on the tip-clerance vortex; extensive numerical computations along with the construction of a surrogate model will be used in the initial phase of control-device optimization; although experimental data from this configuration cannot be directly transposed to compressor-control, they will be used instead to enhance our (limited under the present state-of-the-art) understanding of the influence of these parameters on the evolution of the tip-clearance vortex; furthermore, detailed measurements (LDV/PIV, hot-wire, multihole probes) will be acquired to construct a detailed data-base for LES multiequation subgrid turbulence model validation. Extensive CFD computations, including advanced RANS models (2-equation, rij-eps and a new 12-equation rij-epsij model; ONERA, UPMC), zonal hybrid RANS/LES (ZDES; ONERA) and VR-LES (variable resolution multi-equation subgrid modelling; UPMC) will be systematically compared with measurements to assess the ability of various levels of modelling to predict the time-dependent controlled flow. The large number of experimental and computational data will be specifically assessed to determine (1) the performance of different levels of CFD modelling for actively-controlled aeroengine compressors, (2) the possiblity of detecting and using precursors to trigger active control, (3) guidelines for optimal active-flow-control strategy, and (4) directives for future work.