Multiscale physics

Because of the structural complexity and multi-physics character of modem DAFCs, an analysis through a consistent multiscale physical modeling approach is required to elucidate the efficiency limitations and their location, the degradation and failure mechanisms. 

Lopes Oliveira LF, Laref S, Mayousse E, Jallut C, Franco AA (2012) A multiscale physical model for the transient analysis of PEM Water Electrolyzer Anodes. Phys Chem Chtan Phys 14 10215-10224... 

One possible way to treat chemical dynamics in a large molecular system involved with nonadiabatic electron dynamics is to divide the system into the electron mixing part and the rest. Methodologies in multiscale physics... 

Figure 55. Physical model for multiscale modelling of particle-fluid system.

Hughes, T. J. R., A. A. Oberai, and L. Mazzei (2001a). Large eddy simulation of turbulent channel flows by the variational multiscale method. Physics of Fluids 13, 1784-1799. 

To account for the effect of a sufficiently broad, statistical distribution of heterogeneities on the overall transport, we can consider a probabilistic approach that will generate a probability density function in space (5) and time (t), /(i, t), describing key features of the transport. The effects of multiscale heterogeneities on contaminant transport patterns are significant, and consideration only of the mean transport behavior, such as the spatial moments of the concentration distribution, is not sufficient. The continuous time random walk (CTRW) approach is a physically based method that has been advanced recently as an effective means to quantify contaminant transport. The interested reader is referred to a detailed review of this approach (Berkowitz et al. 2006). 

Computational fluid Melt/solids physics Multiscale transport and... 

The main purpose of quantum-chemical modeling in materials simulation is to obtain necessary input data for the subsequent calculations of thermodynamic and kinetic parameters required for the next steps of multiscale techniques. Quantum-chemical calculations can also be used to predict various physical and chemical properties of the material in hand (the growing film in our case). Under quantum-chemical, we mean here both molecular and solid-state techniques, which are now implemented in numerous computer codes (such as Gaussian [25], GAMESS [26], or NWCHEM [27] for molecular applications and VASP [28], CASTEP [29], or ABINIT [30] for solid-state applications). 

One effective hierarchical method for multiscale bridging is the use of thermodynamically constrained internal state variables (IS Vs) that can be physically based upon microstructure-property relations. It is a top-down approach, meaning the IS Vs exist at the macroscale but reach down to various subscales to receive pertinent information. The ISV theory owes much of its development to the state variable thermodynamics constructed by Helmholtz [4] and Maxwell [5]. The notion of ISV was introduced into thermodynamics by Onsager [6, 7] and was applied to continuum mechanics by Eckart [8, 9]. 

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