MD Modeling of Multiphase Fluid Flows using...

Couette Flow Continuum • Provides reliable results provided a system’s Knudson number is <1 • Models macro-systems well • No slip at fluid/solid interfaces • Governed by incompressible Navier-Stokes equations MD • Atomistic approach models nano domain flow phenomena • Simulations using the Lennard-Jones potential model • Slip occurs at interfaces V (y,t) U y Abstract To further develop a coupled computational fluid dynamic (CFD) - molecular dynamic (MD) scheme for simulating multi-scale fluidic systems containing multiple phases, the LAMMPS package was employed to simulate sudden-start Couette flow in a purely MD regime. These LAMMPS simulations show quantitative agreement with the results of analytical solutions and provide a basis for the application of hybrid CFD-MD analysis in multiphase systems using a file-based information exchange interface between LAMMPS and ANSYS/FLUENT. This work will ultimately enable simulation of interactions between complex biomaterials and of fluidic engineering systems operating on a micro or nano scale. Acknowledgements This material is based upon work supported by the National Science Foundation under award OCI-1005165 with additional support from the Center for Computation & Technology at Louisiana State University. Future Plans • Transition CFD + MD hybridization to multiphase Couette flows • Determine the critical thickness of the film next to the wall • Adapt the hybridization to additional fluidic systems MD Modeling of Multiphase Fluid Flows using LAMMPS Sam Woodham, Kasra Fattah-Hesary, Dr. Dimitris Nikitopoulos Department of Mechanical Engineering, LSU Install LAMMPS to HPC directory and prepare simulation workspace Define simulation environment and characterize the initial particle dynamics Submit job on HPC system and specify desired LAMMPS output Numerical analysis of data and visualization of flow elements LAMMPS Implementation • Developed at Sandia National Laboratories • Highly scalable, efficient parallel MD computing • Open source and widely implemented in various scientific disciplines • Utilized LSU HPC Philip and LONI Queen Bee and Poseidon Simulation Workflow Molecular Dynamics Simulation of Couette Flow (Visualized in VMD) Upper Plate (at velocity U) Phase I Phase II Phase I Lower Plate (static) - MD Simulation - Analytical Solution MD + CFD Hybridization LAMMPS and ANSYS/FLUENT Interface • MD average particle velocity in target bin passed to CFD • CFD updates boundary conditions based on received velocities Couette Flow Analysis (Pure MD) Velocity Profiles at Different Times of Sudden-Start Couette Flow • Low speed disparity due to small sample size and by perturbations induced by the wall surface geometry Phase I Phase II ε 1.0 1.0 σ 1.0σ I 1.986σ I ρ 0.7 σ I 3 0.85 σ II 3 μ 1.21ε I -1 τ I -1 σ I 3 2.63ε II -1 τ II -1 σ II 3 T 1.1 ε I /k B 1.1 ε II /k B

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Page 1: MD Modeling of Multiphase Fluid Flows using LAMMPSreu.cct.lsu.edu/documents/2012-posters/SamWoodham_SURFPoster.pdf · LAMMPS Implementation! • Developed at Sandia National Laboratories!

Couette Flow!

!Continuum!•  Provides reliable results provided a system’s Knudson number is <1!•  Models macro-systems well!•  No slip at fluid/solid interfaces!•  Governed by incompressible Navier-Stokes equations!

!MD!

•  Atomistic approach models nano domain flow phenomena!•  Simulations using the Lennard-Jones potential model!•  Slip occurs at interfaces!

V (y, t)

Abstract!!

To further develop a coupled computational fluid dynamic (CFD) - molecular dynamic (MD) scheme for simulating multi-scale fluidic systems containing multiple phases, the LAMMPS package was employed to simulate sudden-start Couette flow in a purely MD regime. These LAMMPS simulations show quantitative agreement with the results of analytical solutions and provide a basis for the application of hybrid CFD-MD analysis in multiphase systems using a file-based information exchange interface between LAMMPS and ANSYS/FLUENT. This work will ultimately enable simulation of interactions between complex biomaterials and of fluidic engineering systems operating on a micro or nano scale.!!

Acknowledgements!!

This material is based upon work supported by the National Science Foundation under award OCI-1005165 with additional support from the Center for Computation & Technology at Louisiana State University.!

Future Plans!•  Transition CFD + MD hybridization to multiphase Couette flows!•  Determine the critical thickness of the film next to the wall!•  Adapt the hybridization to additional fluidic systems!

MD Modeling of Multiphase Fluid Flows using LAMMPS!

!Sam Woodham, Kasra Fattah-Hesary, Dr. Dimitris Nikitopoulos!

Department of Mechanical Engineering, LSU!

Install LAMMPS to HPC directory and prepare simulation

workspace!

Define simulation environment and

characterize the initial particle dynamics!

Submit job on HPC system and specify desired LAMMPS

output!

Numerical analysis of data and visualization

of flow elements!

LAMMPS Implementation!

•  Developed at Sandia National Laboratories!•  Highly scalable, efficient parallel MD computing!•  Open source and widely implemented in various scientific disciplines!•  Utilized LSU HPC Philip and LONI Queen Bee and Poseidon!

!Simulation Workflow!

Molecular Dynamics Simulation of Couette Flow (Visualized in VMD)!

Upper Plate (at velocity U)!

Phase I!

Phase II!

Phase I!

Lower Plate (static)!

- MD Simulation! - Analytical Solution!

MD + CFD Hybridization!!!!!!!!!!!!!!

!LAMMPS and ANSYS/FLUENT Interface!•  MD average particle velocity in target bin passed to CFD!•  CFD updates boundary conditions based on received velocities!

!!!!!!!!!!!!!!!!

Couette Flow Analysis (Pure MD)

Velocity Profiles at Different Times of Sudden-Start Couette Flow!!!!

•  Low speed disparity due to small sample size and by perturbations induced by the wall surface geometry!

Phase I! Phase II!

ε! 1.0! 1.0!

σ! 1.0σI! 1.986σI!

ρ! 0.7 σI3! 0.85 σII

μ! 1.21εI-1τI

-1σI3! 2.63εII

-1τII-1σII

T! 1.1 εI/kB! 1.1 εII/kB!