Welcome to the homepage of the section Multi-scale Engineering Fluid Dynamics.

Info: prof.dr.ir. Harald van Brummelen (e.h.v.brummelen@remove-this.tue.nl)

The Multi-scale Engineering Fluid Dynamics has recently been established within the framework of the 3TU Centre of Excellence for Multiscale Phenomena. The MEFD section focuses on the development, analysis and application of mathematical-physical models and advanced numerical techniques for multiscale flow problems in engineering applications, with particular emphasis on flow problems in the transitional molecular/continuum regime and auxiliary field interactions. The research in the section has an underpinning and methodological character, while maintaining a strong connection to applications in the high-tech industry and in other sections.

Goal-oriented error estimation and optimal adaptive refinement

In many engineering applications, interest is restricted to a single quantity. For instance, in heat transfer applications, it is ultimately only the heat flux through a certain part of the boundary that is of interest. A crucial notion concerns the fact that the restricted interest to one particular goal functional can be exploited to reduce the complexity of numerical simulation methods. This notion is formalized by so-called goal-oriented a-posteriori error estimation and optimal adaptive-refinement methodologies. By means of the solution of an appropriate dual problem, the contribution of local errors in the solution to the error in the goal functional can be established. Only the regions that have a pronounced influence on the error in the goal functional need to be refined in the numerical model. Such an approach can be used for both discretization adaptivity and model adaptivity. In the first form of adaptivity, the computational mesh (h) or order of approximation (p) is locally adapted to reduce the error. In the second form of adaptivity, the underlying model is locally adapted, e.g., by locally replacing a continuum model by a molecular model.

Multiscale modelling in airbag-deployment simulations

Airbags can cause severe injuries to a passenger if impact occurs before full deployment. To prevent such out-of-position situations, a precise understanding of the dynamics of the airbag is required. Numerical simulations can provide valuable information on the dynamical behaviour of an airbag. However, the numerical simulation of airbag-deployment dynamics is a complicated endeavor, on account of the large range of length scales that the airbag traverses during the deployment process. The initial stowed or folded configuration of the airbag can be characterized as a labyrinth of extremely thin folds. As the inflator is fired, the labyrinth is perfused by the inflator gas. The corresponding pressurization causes the folds to expand and, ultimately, the airbag to unfold into its bulbous final configuration. The perfusion and the corresponding expansion and unfolding constitute a multiscale fluid-structure-interaction problem of very high complexity, in which the microscale associated with the many tiny folds in the initial configuration is connected to the macroscale pertaining to the final configuration. Hence, the characteristic length scale of the airbag geometry changes by many orders