Embedded Software V&V using Virtual Platforms for Powertrain applications

International audienceCurrent development trends for automotive products are driven by time to market reduction, cost optimization, and quality improvement. Dual to these business constraints are demands for innovation and safety conformance which impose increasing complexity on embedded systems. To address these challenges impacting software and hardware to improve system dependability, new methodology and tools need to be set-up. The use of representative virtual platforms combining speed and accuracy allows earlier software development, improved system testing, and fault injection analysis, with a high potential for reuse of system IPs (including both hardware and software). In this paper, we will present investigation on new methods and associated results using a simplified virtual platform to test a powertrain application

Unsteady coupling of Navier-Stokes and radiative heat transfer solvers applied to an anisothermal multicomponent turbulent channel flow

Eurotherm Seminar 83 on Computational Thermal Radiation in Participating Media III, Lisbon, PORTUGAL, APR 15-17, 2009International audienceDirect numerical simulations (DNS) of an anisothermal reacting turbulent channel flow with and without radiative source terms have been performed to study the influence of the radiative heat transfer on the optically non-homogeneous boundary layer structure. A methodology for the study of the emitting/absorbing turbulent boundary layer (TBL) is presented. Details on the coupling strategy and the parallelization techniques are exposed. An analysis of the first order statistics is then carried out. It is shown that, in the studied configuration, the global structure of the thermal boundary layer is not significantly modified by radiation. However, the radiative transfer mechanism is not negligible and contributes to the heat losses at the walls. The classical law-of-the-wall for temperature can thus be improved for RANS/LES simulations taking into account the radiative contribution

Effects of radiative heat transfer on the structure of turbulent supersonic channel flow

International audienceThe interaction between turbulence in a minimal supersonic channel and radiative heat transfer is studied using large-eddy simulation. The working fluid is pure water vapour with temperature-dependent specific heats and molecular transport coefficients. Its line spectra properties are represented with a statistical narrow-band correlated-k model. A grey gas model is also tested. The parallel no-slip channel walls are treated as black surfaces concerning thermal radiation and are kept at a constant temperature of 1000 K. Simulations have been performed for different optical thicknesses (based on the Planck mean absorption coefficient) and different Mach numbers. Results for the mean flow variables, Reynolds stresses and certain terms of their transport equations indicate that thermal radiation effects counteract compressibility (Mach number) effects. An analysis of the total energy balance reveals the importance of radiative heat transfer, compared to the turbulent and mean molecular heat transport

Application of particle filters to regional-scale wildfire spread

European Conference on Thermophysical Properties (ECTP)European Conference on Thermophysical Properties (ECTP), Porto, PORTUGALPorto, PORTUGAL, SEP 05-05, 2014SEP 05-05, 2014International audienceThis paper demonstrates the capability of particle filters for sequentially improving the simulation and forecast of wildfire propagation as new fire front observations become available. Particle filters, also called Sequential Monte Carlo (SMC) methods, fit into the domain of inverse modeling procedures, where measurements are incorporated (assimilated) into a computational model so as to formulate some feedback information on the uncertain model state variables and/or parameters, through representations of their probability density functions (PDF). Based on a simple sampling importance distribution and resampling techniques, particle filters combine Monte Carlo samplings with sequential Bayesian filtering problems. This study compares the performance of the Sampling Importance Resampling (SIR) and of the Auxiliary Sampling Importance Resampling (ASIR) filters for the sequential estimation of a progress variable and of vegetation parameters of the Rate Of fire Spread (ROS) model, which are all treated as state variables. They are applied to a real-world case corresponding to a reduced-scale controlled grassland fire experiment for validation; results indicate that both the SIR and the ASIR filters are able to accurately track the observed fire fronts, with a moderate computational cost. Particle filters show, therefore, their good ability to predict the propagation of controlled fires and to significantly increase fire simulation accuracy. While still at an early stage of development, this data-driven strategy is quite promising for regional-scale wildfire spread forecasting

What’s new on physiology and virulence factors of Scedosporium apiospermum ?

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On the interaction of vortices with mixing layers

We describe the perturbations introduced by two counter-rotating vortices - in a two-dimensional configuration - or by a vortex ring - in an axisymmetric configuration - to the mixing layer between two counterflowing gaseous fuel and air streams of the same density. The analysis is confined to the near stagnation point region, where the strain rate of the unperturbed velocity field, A0, is uniform. We restrict our attention to cases where the typical distance 2r0 between the vortices - or the characteristic vortex ring radius r0 - is large compared to both the thickness, δv, of the vorticity core and the thickness, δm∼(ν/A0)1/2, of the mixing layer. In addition, we consider that the ratio, Γ/ν, of the vortex circulation, Γ, to the kinematic viscosity, ν, is large compared to unity. Then, during the interaction time, A0,-1, the viscous and diffusion effects are confined to the thin vorticity core and the thin mixing layer, which, when seen with the scale r0, appears as a passive interface between the two counterflowing streams when they have the same density. In this case, the analysis provides a simple procedure to describe the displacement and distortion of the interface, as well as the time evolution of the strain rate imposed on the mixing layer, which are needed to calculate the inner structure of the reacting mixing layer as well as the conditions for diffusion flame extinction and edge-flame propagation along the mixing layer. Although in the reacting case variable density effects due to heat release play an important role inside the mixing layer, in this paper the analysis of the inner structure is carried out using the constant density model, which provides good qualitative understanding of the mixing layer response

Applying a science‐based systems perspective to dispel misconceptions about climate effects of forest bioenergy

The scientific literature contains contrasting findings about the climate effects of forest bioenergy, partly due to the wide diversity of bioenergy systems and associated contexts, but also due to differences in assessment methods. The climate effects of bioenergy must be accurately assessed to inform policy-making, but the complexity of bioenergy systems and associated land, industry and energy systems raises challenges for assessment. We examine misconceptions about climate effects of forest bioenergy and discuss important considerations in assessing these effects and devising measures to incentivize sustainable bioenergy as a component of climate policy. The temporal and spatial system boundary and the reference (counterfactual) scenarios are key methodology choices that strongly influence results. Focussing on carbon balances of individual forest stands and comparing emissions at the point of combustion neglect system-level interactions that influence the climate effects of forest bioenergy. We highlight the need for a systems approach, in assessing options and developing policy for forest bioenergy that: (1) considers the whole life cycle of bioenergy systems, including effects of the associated forest management and harvesting on landscape carbon balances; (2) identifies how forest bioenergy can best be deployed to support energy system transformation required to achieve climate goals; and (3) incentivizes those forest bioenergy systems that augment the mitigation value of the forest sector as a whole. Emphasis on short-term emissions reduction targets can lead to decisions that make medium- to long-term climate goals more difficult to achieve. The most important climate change mitigation measure is the transformation of energy, industry and transport systems so that fossil carbon remains underground. Narrow perspectives obscure the significant role that bioenergy can play by displacing fossil fuels now, and supporting energy system transition. Greater transparency and consistency is needed in greenhouse gas reporting and accounting related to bioenergy