An adaptive preconditioner for steady incompressible flows

This paper describes an adaptive preconditioner for numerical continuation of incompressible Navier--Stokes flows. The preconditioner maps the identity (no preconditioner) to the Stokes preconditioner (preconditioning by Laplacian) through a continuous parameter and is built on a first order Euler time-discretization scheme. The preconditioner is tested onto two fluid configurations: three-dimensional doubly diffusive convection and a reduced model of shear flows. In the former case, Stokes preconditioning works but a mixed preconditioner is preferred. In the latter case, the system of equation is split and solved simultaneously using two different preconditioners, one of which is parameter dependent. Due to the nature of these applications, this preconditioner is expected to help a wide range of studies

Emergence of stochastic dynamics in plane Couette flow

Spatially localized states play an important role in transition to turbulence in shear flows (Kawahara, Uhlmann & van Veen, Annu. Rev. Fluid Mech. 44, 203 (2012)). Despite the fact that some of them are attractors on the separatrix between laminar and turbulent flows, little is known of their dynamics. We investigate here the temporal dynamics of such steady spatially localized solutions in the context of plane Couette flow. These solutions exist on oscillating branches in parameter space. We consider the saddle-nodes of these branches as initial conditions of simulations run with offset Reynolds numbers. We observe a relaminarization regime mostly characterized by deterministic dynamics and identify within this regime the existence of parameter intervals in which the results are stochastic and long-lived chaotic transients are observed. These results are obtained below the threshold for transition, shed light on the emergence of stochasticity in transitional plane Couette flow and will likely inform a range of shear flow configurations

FROM TECHNOLOGY COMPETITION TO REINVENTING INDIVIDUAL MOBILITY FOR A SUSTAINABLE FUTURE: CHALLENGES FOR NEW DESIGN STRATEGIES FOR ELECTRIC VEHICLE

Emissions reduction constraints as well as petrol costs create new opportunities for radical innovations in powertrain solutions for automobiles. In this paper, we focus on the on-going revival of full battery electric vehicles (EV). Our analysis is drawn in two axes. First, we analyse of the on-going context for such EV. As electricity is surely not a new option for automobile industry, we study the past attempts that failed, and show that it is possible to highlight some conditions for a future success and to see why there is nowadays a new window of opportunity for a large scale roll-out of EV. Our reasoning is based both on market evolution as well as technological evolutions. The recent developments around EV suggest that many of the conditions for a successful tidal wave are about to be combined. Second, we characterize the innovation & design strategy that an OEM needs to implement in order to turn this opportunity into a profitable competitive advantage: -Innovation strategy has to expand the scope of design dimensions from electrification of Internal Combustion Engine (ICE) vehicles to the complete redefinition of a specific electric product solution. Beyond the product scope, we will see that electric mobility services can provide an efficient enabler to overcome the operational and maintenance pitfalls of electric solutions. -Marketing strategy also needs to dramatically revise the classical auto marketing approach, as electric mobility will require new behaviours from end users as well as favourable regulations and infrastructures from local authorities. -Development processes cannot rely only on the traditional automotive ecosystem, because many competencies required for EV have to be created during the development process. On going EV projects will need a deep rethinking of design system to acquire the new competencies In this paper, we will discuss first outputs from a long term (4 years) action-research launched at the end of 2007. This research is done at an OEM committed to launch a full range of EV, and which, as a consequence, already faces all the challenges related to such a radical innovation.

Crossing innovation and product projects management: comparative analysis in the automotive industry.

Projectification and platform approaches have been two main transformation trends implemented by industrial firms during the1990s. For those firms, innovation management no longer deals with introducing radically and totally new products, but rather withapplying innovative features within a regular stream of products and platforms. This paper proposes an analytical framework thatcan address the resulting interplay between innovative features and new products. This framework relies on the concept of innovationlife-cycle management (ILCM). The paper presents the early results from the comparison of five case studies from three OEMs.Organizational learning; New product projects portfolio; Innovation management; Automotive industry; Comparative analysis.

FROM TECHNOLOGY COMPETITION TO REINVENTING INDIVIDUAL MOBILITY FOR A SUSTAINABLE FUTURE: CHALLENGES FOR NEW DESIGN STRATEGIES FOR ELECTRIC VEHICLE

Ceris-Cnr Collegio Carlo Alberto - Via Real Collegio 30 Moncalieri (Turin, Italie). Actes en ligne : http://www.gerpisa.univ-evry.fr/rencontre/16.rencontre/GERPISAJune2008/home.htmlEmissions reduction constraints as well as petrol costs create new opportunities for radical innovations in powertrain solutions for automobiles. In this paper, we focus on the on-going revival of full battery electric vehicles (EV). Our analysis is drawn in two axes. First, we analyse of the on-going context for such EV. As electricity is surely not a new option for automobile industry, we study the past attempts that failed, and show that it is possible to highlight some conditions for a future success and to see why there is nowadays a new window of opportunity for a large scale roll-out of EV. Our reasoning is based both on market evolution as well as technological evolutions. The recent developments around EV suggest that many of the conditions for a successful tidal wave are about to be combined. Second, we characterize the innovation & design strategy that an OEM needs to implement in order to turn this opportunity into a profitable competitive advantage: -Innovation strategy has to expand the scope of design dimensions from electrification of Internal Combustion Engine (ICE) vehicles to the complete redefinition of a specific electric product solution. Beyond the product scope, we will see that electric mobility services can provide an efficient enabler to overcome the operational and maintenance pitfalls of electric solutions. -Marketing strategy also needs to dramatically revise the classical auto marketing approach, as electric mobility will require new behaviours from end users as well as favourable regulations and infrastructures from local authorities. -Development processes cannot rely only on the traditional automotive ecosystem, because many competencies required for EV have to be created during the development process. On going EV projects will need a deep rethinking of design system to acquire the new competencies In this paper, we will discuss first outputs from a long term (4 years) action-research launched at the end of 2007. This research is done at an OEM committed to launch a full range of EV, and which, as a consequence, already faces all the challenges related to such a radical innovation

Structural evolution of PVDF during storage or annealing

The effect of annealing PVDF at temperatures above Tg and below Tm was investigated by differential scanning calorimetry (DSC), thermostimulated current spectroscopy (TSC) and solid-state NMR. This study evidences a progressive structural evolution, taking place during such annealing. Its characteristics (kinetics and its temperature dependence, lack of reversibility at lower temperature over extended periods of time, double organization corresponding to double annealing with unmodified kinetics) point to a mechanism of secondary crystallization as described by Marand et al. In addition to the formation of extra crystalline (hence rigid) material, this phenomenon is believed to generate increasing conformational constraints in the residual amorphous material. Accordingly, a progressive reduction of the molecular mobility was demonstrated by NMR during annealing

Modulated patterns in a reduced model of a transitional shear flow

We consider a close relative of plane Couette flow called Waleffe flow in which the fluid is confined between two free-slip walls and the flow driven by a sinusoidal force. We use a reduced model of such flows constructed elsewhere to compute stationary exact coherent structures of Waleffe flow in periodic domains with a large spanwise period. The computations reveal the emergence of stationary states exhibiting strong amplitude and wavelength modulation in the spanwise direction. These modulated states lie on branches exhibiting complex dependence on the Reynolds number but no homoclinic snaking

Homoclinic snaking of localized states in doubly diffusive convection

Numerical continuation is used to investigate stationary spatially localized states in two-dimensional thermosolutal convection in a plane horizontal layer with no-slip boundary conditions at top and bottom. Convectons in the form of 1-pulse and 2-pulse states of both odd and even parity exhibit homoclinic snaking in a common Rayleigh number regime. In contrast to similar states in binary fluid convection, odd parity convectons do not pump concentration horizontally. Stable but time-dependent localized structures are present for Rayleigh numbers below the snaking region for stationary convectons. The computations are carried out for (inverse) Lewis number \tau = 1/15 and Prandtl numbers Pr = 1 and Pr >> 1