# NSU Research Contributions

### Title : Graphics Process Unit based Multiple-Relaxation-Time Lattice Boltzmann Simulation of Non-Newtonian Fluid Flows in a Backward Facing Step

**Authors : **M. M. Molla, P. Nag, S. Thohura, A.

**Abstract : **A modified power-law (MPL) viscosity model of non-Newtonian fluid flow has been used
for the multiple-relaxation-time (MRT) lattice Boltzmann methods (LBM) and then validated with the
benchmark problems using the graphics process unit (GPU) parallel computing via Compute Unified
Device Architecture (CUDA) C platform. The MPL model for characterizing the non-Newtonian
behavior is an empirical correlation that considers the Newtonian behavior of a non-Newtonian
fluid at a very low and high shear rate. A new time unit parameter (l) governing the flow has
been identified, and this parameter is the consequence of the induced length scale introduced by the
power law. The MPL model is free from any singularities due to the very low or even zero shear-rate.
The proposed MPL model was first validated for the benchmark study of the lid-driven cavity and
channel flows. The model was then applied for shear-thinning and shear-thickening fluid flows
through a backward-facing step with relatively low Reynolds numbers, Re = 100–400. In the case
of shear-thinning fluids (n = 0.5), laminar to transitional flow arises while Re 300, and the large
vortex breaks into several small vortices. The numerical results are presented regarding the velocity
distribution, streamlines, and the lengths of the reattachment points.

Journal : Computation |
Volume : 8 |
Year : 2020 |
Issue : 83 |

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