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174 results on '"Nieken U"'

4. Mesoscopic simulation of diffusive contaminant spreading in gas flows at low pressure

Author

Schmieschek, S., Sinz, D. K. N., Keller, F., Nieken, U., and Harting, J.

Subjects
Physics - Fluid Dynamics, Condensed Matter - Statistical Mechanics, Physics - Computational Physics
Abstract

Many modern production and measurement facilities incorporate multiphase systems at low pressures. In this region of flows at small, non-zero Knudsen- and low Mach numbers the classical mesoscopic Monte Carlo methods become increasingly numerically costly. To increase the numerical efficiency of simulations hybrid models are promising. In this contribution, we propose a novel efficient simulation approach for the simulation of two phase flows with a large concentration imbalance in a low pressure environment in the low intermediate Knudsen regime. Our hybrid model comprises a lattice-Boltzmann method corrected for the lower intermediate Kn regime proposed by Zhang et al. for the simulation of an ambient flow field. A coupled event-driven Monte-Carlo-style Boltzmann solver is employed to describe particles of a second species of low concentration. In order to evaluate the model, standard diffusivity and diffusion advection systems are considered., Comment: 9 pages, 8 figures

Published
2015

36. Modeling the dynamics of partial wetting

Author

Huber, M., Säckel, W., Hirschler, M., Hassanizadeh, S.M., Nieken, U., Environmental hydrogeology, and Hydrogeology

Subjects
partial wetting, surface tension, SPH, moving contact line, dynamic contact angle
Abstract

The behavior of interfaces and contact lines arises from intermolecular interactions like Van der Waals forces. To consider this multi–phase behavior on the continuum scale, appropriate physical descriptions must be formulated. While the Continuum Surface Force model is well–engineered for the description of interfaces, there is still a lack of treatment of contact lines, which are represented by the intersection of a fluid–fluid interface and a solid boundary surface. In our approach we use the “non compensated Young force” to model contact line dynamics and therefore use an extension to the Navier–Stokes equations in analogy to the extension of a two–phase interface in the CSF model. Because particle–based descriptions are well–suited for changing and moving interfaces we use Smoothed Particle Hydrodynamics. In this way we are not only able to calculate the equilibrium state of a two–phase interface with a static contact angle, but also for instance able to simulate droplet shapes and their dynamical evolution with corresponding contact angles towards the equilibrium state, as well as different pore wetting behavior. Together with the capability to model density differences, this approach has a high potential to model recent challenges of two–phase transport in porous media. Especially with respect to moving contact lines this is a novelty and indispensable for problems, where the dynamic contact angle dominates the system behavior.

Published
2013

43. Modeling the dynamics of partial wetting

Author

Environmental hydrogeology, Hydrogeology, Huber, M., Säckel, W., Hirschler, M., Hassanizadeh, S.M., Nieken, U., Environmental hydrogeology, Hydrogeology, Huber, M., Säckel, W., Hirschler, M., Hassanizadeh, S.M., and Nieken, U.

Published
2013

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