Prof. Eirik Grude Flekkøy
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Hybrid models and coupling schemes to deal with different scales
Most interesting applications of physics-based computer simulations involve the description of very different spatial or temporal scales. There are several ways to attack the problems that arise when several scales must be simulated at the same time. I will discuss a few of them in the three lectures:1 Hybrid models and coupling shcemes: How can a particle description be coupled to a continuum description of smaller resolution? Here the particles and the continuum represents the same underlying physical system, which is then represented in greater detail in some parts of space than in others. The construction of an interface to couple the two descriptions is useful for boundary layers and singular hydrodynamic behavior. Some existing couplings strategies are discussed and illustrated with computer simulations.
2. Fluid-- particle systems. In such systems the challenge is to choose the right level of coarse graining of the fluid and the particles and then couple the two phases. Some examples of how this may be done is discussed and illustrated with computer simulations, some of which are subjected to detailed comparison with lab-experiments.
3. Dissipative particle dynamics and the attempts to derive it from an underlying micro-world: This model, which will also be discussed by Pep Espanol represents another way to approach the problem of different scales, or rather choosing the appropriate scale for the application at hand. This is done by interpreting each single particle as a mesoscopic representative of many underlying molecules. Experiences with the resulting such a model that involves a Voronoi -lattice are discussed.