SC²S Colloquium - May 20, 2015

From Sccswiki
Jump to navigation Jump to search
Date: May 20, 2015
Room: 02.07.023
Time: 3:00 pm, s.t.

Ravikishore Kommajosyula: Development of a Numerical scheme for Transient Coupled Lattice-Boltzmann - Navier-Stokes Simulations

In the thesis we present a three-dimensional transient coupled solver composed of a finite-difference Navier-Stokes (NS) solver and a Lattice Boltzmann (LB) solver. The NS and LB solvers work on independent parts of the domain and are coupled at their boundaries. Such an approach llows for easier representation of additional dynamics in regions where their activity is high, while resolving the rest of the system with a cheaper solver, thus providing a compromise between physical accuracy and computational complexity.

In the previous works, a steady-state algorithm for simulating fluid-flow using a three-dimensional coupled LB-NS solver, and the methods for transferring and converting values between the subdomains have been developed. In the scope of this thesis, we extend the steady-state coupling algorithm to include time-dependent phenomenon. The Multiple-Relaxation-Time (MRT) collision operator is integrated into the coupling algorithm, to deal with the low viscosities that arise on the LB subdomain in transient problems, thereby enhancing the lowest limit of viscosity that can be simulated, by 4 times. The coupled LB-NS solver is validated by running steady-state channel flow scenarios, for which the analytical results are known, and the corresponding results are presented.

The time-dependent behavior is tested by applying an oscillating input velocity condition for the channel flow scenario and comparing the results of the coupled LB-NS simulation, to that of the standalone NS solver used in the coupled solver. A parametric study involving various simulation parameters, and their influence on the result are presented. To the author's knowledge, this work provides the first literature and software for transient coupled LB-NS fluid flow simulations.