Time filter

Source Type

Kamrin K.,Massachusetts Institute of Technology | Koval G.,National Institute for Applied Sciences, Strasbourg
Physical Review Letters | Year: 2012

Extending recent modeling efforts for emulsions, we propose a nonlocal fluidity relation for flowing granular materials, capturing several known finite-size effects observed in steady flow. We express the local Bagnold-type granular flow law in terms of a fluidity ratio and then extend it with a particular Laplacian term that is scaled by the grain size. The resulting model is calibrated against a sequence of existing discrete element method data sets for two-dimensional annular shear, where it is shown that the model correctly describes the divergence from a local rheology due to the grain size as well as the rate-independence phenomenon commonly observed in slowly flowing zones. The same law is then applied in two additional inhomogeneous flow geometries, and the predicted velocity profiles are compared against corresponding discrete element method simulations utilizing the same grain composition as before, yielding favorable agreement in each case. © 2012 American Physical Society. Source

Martin N.,Jet Propulsion Laboratory | Monnier J.,National Institute for Applied Sciences, Strasbourg
European Journal of Mechanics, B/Fluids | Year: 2015

The present work addresses the question of performing inverse rheometry and basal properties inference for pseudoplastic gravity-driven free-surface flows at low Reynolds' number. The modeling of these flows involves several parameters, such as the rheological ones or the state of the basal boundary (modeling an interface between the base and the fluid). The issues of inverse rheometry are addressed in a general laboratory flow context using surface velocity data. The inverse characterization of the basal boundary is proposed in a geophysical flow context where the parameters involved in the empirical effective sliding law are particularly difficult to estimate. Using an accurate direct and inverse model based on the adjoint method combined with an original efficient solver, sensitivity analyses and parameter identification are performed for a wide range of flow regimes, defined by the degree of slip and the non-linearity of the viscous sliding law considered at the bottom. The first result is the numerical assessment of the passive aspect of the viscosity singularity inherent to a power-law pseudoplastic (shear-thinning) description in terms of surface velocities. From this result, identification of the two parameters of the constitutive law, namely the power-law exponent and the consistency, are performed. These numerical experiments provide, on the one hand, a very robust identification of the power-law exponent, even for very noisy surface velocity observations and on the other hand, a strong equifinality problem on the identification of the consistency. This parameter has a minor influence on the flow, in terms of surface velocities. Typically for temperature-dependent geophysical fluids, a law describing a priori its spatial variability is then sufficient (e.g. based on a temperature vertical profile). This study then focuses on the basal properties interacting with the fluid rheology. An accurate joint identification of the scalar valued triple (n,m;β) (respectively the rheological exponent, the non linear friction exponent and the friction coefficient) is achieved for any degree of slip, allowing to completely infer the flow regime. Next, in a geophysical flow context, identifications of a spatially varying friction coefficient are performed for various perturbed bedrock topography. The (2D-vertical) results demonstrate a severely ill-posed problem that allows to compute a given set of surface velocity data with different topography/friction pairs. Source

Newall A.T.,University of New South Wales | Wood J.G.,University of New South Wales | Oudin N.,National Institute for Applied Sciences, Strasbourg | MacIntyre C.R.,University of New South Wales
Emerging Infectious Diseases | Year: 2010

We used a hybrid transmission and economic model to evaluate the relative merits of stockpiling antiviral drugs and vaccine for pandemic influenza mitigation. In the absence of any intervention, our base-case assumptions generated a population clinical attack rate of 31.1%. For at least some parameter values, population prepandemic vaccination strategies were effective at containing an outbreak of pandemic influenza until the arrival of a matched vaccine. Because of the uncertain nature of many parameters, we used a probabilistic approach to determine the most cost-effective strategies. At a willingness to pay of >A$24,000 per life-year saved, more than half the simulations showed that a prepandemic vaccination program combined with antiviral treatment was cost-effective in Australia. Source

Agency: Cordis | Branch: FP7 | Program: CSA-CA | Phase: SST-2007-1.2-01;SST-2007-1.2-02 | Award Amount: 1.25M | Year: 2009

The DIREC_MAT project objective is to share, at a European scale, knowledge and practices on recycling road and road-related waste in the aim of ensuring an environmentally-friendly and sustainable end-of-life for road infrastructure. Road material recycling processes have previously been studied in national and European research projects and have led to various levels of practical implementation; unfortunately, the national experiences developed across Europe almost never benefit other European countries. This is especially true for the newer Member States. Furthermore existing knowledge and practices are presently scattered. Reliable practice-oriented data on all types of road materials and waste will be identified and compiled by skilled experts working in both research and construction capacities. Field experience and relevant research issues will be integrated into a Web database to provide the European road community with unrestricted access to updated online data on end products that have been classified, assessed and illustrated with jobsite practices for dismantling and recycling applications. This database will not only offer information to stakeholders on facilitating the correct re-use of road and road-related waste products back into roads without generating health impacts, but will also provide technical and scientific information for CEN Technical Committees. Lastly, such a tool will make it possible to better identify outstanding research needs in this area. Best practice guides on green techniques for recycling road and road-related waste back into roads will be delivered; benchmarking processes will be detailed and shared by all stakeholders in order to achieve a road material recyclability level of nearly 100%. FEHRL (Forum of European Highway Research Laboratories) will contribute by performing decisive clustering tasks and engaging in a comprehensive dissemination plan to promote the required knowledge sharing for end-users

Agency: Cordis | Branch: FP7 | Program: MC-IAPP | Phase: FP7-PEOPLE-2011-IAPP | Award Amount: 1.69M | Year: 2012

The analysis of emerging technologies and their potential impact on markets, economies and societies requires reliable and repeatable methods and tools since the related information plays a critical role for strategic decisions of private and public organizations. All existing techniques reveal several weaknesses such as limited accuracy on middle and long-term forecast; poor repeatability; poor adaptability, i.e. no universal methods are known, besides complementary instruments must be integrated according to the specific goal and data availability. These considerations highlight the need to introduce structured methods and tools capable to support strategic decisions in industrial R&D activities, by managing the multi-disciplinary complexity of current systems and by anticipating the future characteristics of products and processes. The final FORMAT project result will be the development of an innovative forecasting methodology, backed by a web semantic IT tool, supporting decision making in Manufacturing Industries, to be evaluated in real test cases and extensively described in the FORMAT handbook and through an IT demonstrator to proof the concept.

Discover hidden collaborations