Key words: Phase Change Materials (PCM), Suspensions of micro-encapsulated Phase Change Materials (mPCM), Heat transfer, Convection, Physical characterization of mPCM and of the systems, Fluid mechanics, Energetics, urban environment, process optimization. Methodologies: Multi-scale and Multiphysics approaches via experiments and computations. Providing urban thermal comfort and maintaining human mobility in case of icing, snow or heat waves in densely populated areas is of crucial importance in our increasingly urbanized world. The goal of the project Convinces is to investigate reversible systems, cooling during heat waves / heating during icing at strategic urban places via the flow of a microencapsulated Phase Change Materials (mPCM) suspension in the draining layer. In the present project, fundamental and applied research will be carried out to understand physical mechanisms at play in the flow of mPCM suspensions subject to a vertical temperature gradient. Thus, studying buoyancy driven flows in detail is crucial in order to optimize heat transfer. While natural convection involves heat transfer rate enhancement up to 40% during phase transitions, the convective flows of mPCM slurries can involve still better heat transfer. However, in most experimental studies, global temperature measurements have only been obtained by means of thermocouples or IR thermography, since most of the systems are opaque. For similar reasons, local velocity fields are difficult to obtain within the fluid which leads to macroscopic measurements of heat transfer. However, local measurements are required to gain insight regarding the coupling between dynamics and heat transfer as well as to understand physical mechanisms involved. The Convinces project aims at dealing with the mixed convection of mPCM suspensions in porous media considering any relevant scales (from the micron caps to the meter mock-up), facing also with the multi-physics aspects. To achieve this, a wide range of advanced experimental techniques (SThM, laser-based photothermal methods, Digital Holographic Microscopy, IR Thermometry, MRI Velocimetry and Thermometry...) will be implemented to characterize the systems and describe the flows locally. Numerical modeling of these systems is of crucial importance to the success of this project. Sophisticated numerical methods will be implemented. Determining heat transfer in the system (porous layer and surface layer) is also an essential key and a final objective to tend to applicative engineering systems. More particularly, we intend to focus on urban applications (downtown squares, schoolyard, pedestrian area, sidewalks, café terraces, touristic places). Optimizing energy systems places Convinces at the heart of a general thinking on reducing energy consumption supported by “Stratégie Nationale de Recherche sur l'Énergie” (SNRE).

To tackle energy and environmental issues, major advances are expected in the Building sector. Reliable in-situ thermal characterization of buildings before and after a renovation action are required. Moreover, construction must be more "sustainable", notably by using bio-sourced materials and raw earth. In this project, we propose an inter-disciplinary technical solution combining modeling, simulations and measurements for a better in-situ evaluation of the energy performances of conventional and sustainable walls. The identification of the thermal characteristics will be performed by an inverse method combining a hygro-thermal model solved in real time by a "reduced bases" technique and sensors selected by "optimal experimental design". After a robustness study via virtual tests, a prototype will be realized and tested on real walls in laboratory and in the Equipment of Excellence Sense-City.

Flash-flood forecasting is of crucial importance to mitigate the devastating effects of flash-floods. However, its development has experienced serious setbacks, due to the large number of affected catchments, their small surface areas (1 to 500 km²), their very short response times (limited to a few hours), and the limited knowledge of the assets being exposed. First operational flash flood warning systems have recently been implemented in France and other countries. Nevertheless, the capacities of these systems can still largely be improved (limited anticipation, limited geographic coverage, impacts not represented). In this context, the PICS project proposes a step forward by designing and evaluating integrated forecasting chains capable of anticipating the impacts of flash-floods with a few hours lead-time. This objective will be reached through interactions between varied scientific teams (meteorologists, hydrologists, hydraulic engineers, economists, sociologists) and operational actors (civil security, local authorities, insurance companies, hydropower companies, transport network operators). The integrated short-range forecasting (or nowcasting) chains designed in the project will incorporate the following components: high resolution quantitative precipitation estimates and short range precipitation forecasts (or nowcasts), highly distributed rainfall runoff models designed to simulate river discharges in ungauged conditions, DTM based hydraulic models for the delineation of potentially flooded areas, and finally several impacts models aiming to represent varied socio-economic effects: insurance losses, inundation of critical infrastructures, and also dynamic population exposure and vulnerability. The project will work towards: effectively coupling these various modelling components, evaluating these components in terms of uncertainties and complementarity, and finally assessing the capacity of these nowcasting chains to meet the end-users needs. A particular attention will be put on the consistency across the various components of these chains, in terms of variables used, spatial and temporal resolutions, application scale, and degree of uncertainty. One critical aspect of the project will also be the validation of the results based on case studies. The small ungauged basins context, indeed, is generally synonym of serious data scarcity. For this reason, a particular effort will be devoted in the project to the gathering of appropriate validation datasets (impacts, flood areas, etc.) and to define relevant validation strategies. The project will include case studies related to recent extreme rainfall events observed in the French Mediterranean area: June 2010 floods in the Argens basin, September-October 2014 floods in the Gardons, Vidourle, Hérault and Lez watersheds, and October 2015 floods in several small basins in the Alpes Maritimes territory. This list of case studies will be complemented at the beginning of the project based on the exchanges with the end users. The project will also entail significant efforts to improve and adapt the different components involved in the modelling chains: improvement of distributed hydrological modelling in ungauged conditions, qualification of uncertainties on discharges estimates based on rainfall observations and nowcasts, improvement of 1-D approaches and test of a 2-D model for large scale automatic hydraulic computations, and finally adaptation of the impacts models to take benefit from information on flooded areas provided by the forecasting chain. Considering this work program, the project should enable significant breakthroughs in the field of integrated flash floods impacts nowcasting. The wide representation of potential end users in the project, as members of the end-users group and as project partners, should finally facilitate the transfer of project results towards operational applications.

The technique of reinforcemetn of compressible soils by vertical Rigid Inclusions (RI) is very wide-spread in France and abroad. This technique of composite foundation mixing deep and superficial elements, was developed initially for works of embankment (for infrastructures of transport), but extends in wind turbines and also in industrial buildings today (e.g. logistic platforms), of housing or offices (less than 4-5 floors), schools, hospitals, etc. This technique so fits on all the territory, urbi et orbi, impacts on the choice of the foundations of the constructions and the linear works of transport (roads and railroads), so touching in a little visible, but real way, the citizens in their living environment and for their mobility. The issues addressed here concern the behaviour of the RI-reinforced soil mass: i) Dynamic Loads: Modifying the celerity of surface waves in a medium with periodic inclusions ii) under seismic stress: Inertial and kinematic effects The methodology used is based on the experimental approach of physical modelling on reduced models combined with numerical modelling, all in conjunction with the field. The propagation of surface waves in soil is modified by the presence of heterogeneities (vertical RI), but in what way? In order to answer this question, which concerns railway applications as a priority, reduced "geophysical" models will be carried out, based on the principle of scaling wavelengths, and implemented on the Ifsttar MUSC bench. Numerically, the spectral element method associated with the non-periodic homogenization technique will be implemented. In the case of seismicload, the presence of Ri reinforcement necessarily changes the soil response, but in what way? To study the inertial and kinematic effects of an RI-reinforced soft soil, "geotechnical" small scale models will be tested with the earthquake simulator installed in the Ifsttar centrifuge. Here the frequencies are scaled up. A fine dynamic characterization of centrifuge soils will be carried out in parallel.The so-called macro-element numerical method as well as the so-called transfer curves will be implemented for simplified models, while non-linear 3D finite elements will be used to simulate works under seismic load (such as those studied in centrifuge), before moving to parametric studies of reference structures. The consortium set up to try to increase knowledge on these dynamic issues brings together, around the Ifsttar, a set of partners involved to varying degrees from downstream upstream: i) SNCF-reseau, Ménard, LGP, centrale-Supelec; ii) EDF, Cerema, Terrasol, Ménard, centrale-Supélec, centrale Nantes. Exceptional experimental equipment combined with advanced, sophisticated or simplified numerical modelling will allow to observe, understand and simulate different configurations, to bring new knowledge and make it available to the Construction Engineering.

The Relev project aims to develop a transdisciplinary methodology integrating expertise in natural hazards (geography, civil engineering, geology), urban planning (city planning, architecture) and social sciences (psychology, sociology, history) to improve recovery-management post-disaster. The aims of this project are (1) to develop a method to anticipate the management required for post-disaster recovery at the local city scale, and (2) to integrate natural hazards into the urban planning process leading to economically viable sustainable development. Our objective, build on an innovative integrated approach, is to develop new knowledge on the effectiveness of post-disaster recovery strategies and to strengthen the resilience of cities to natural disasters, and hence climate change. We propose to make studies more interdisciplinary conducted on resilience and adaptation to natural risks in order to make available to local and professional decision makers in urban planning and construction integrated tools to help design sustainable cities and secure urban functioning in the face of natural disasters. The main hypothesis of this project is that the reconstruction of a disaster territory following a natural disaster represents a window of opportunity to redevelop the territory in a more resilient and sustainable way against future extreme events. The Relev project team assumes that the first sine qua non condition is anticipation of the management of this period. To meet our objective, we develop an integrated and transdisciplinary approach around 3 components: (1) A state of the art aimed at characterising the diversity of post-disaster reconstruction practices in a territory. The scientific consortium will make a specific effort to realize a post-disaster feedback on the islands of Saint-Martin and Saint-Barthélemy, which have been heavily impacted by Irma Hurricane, (2) Development of a diagnosis of post-disaster local reconstruction conditions, (3) Development of a method to assist in the planning of network reconstruction strategies.