[SY-O3] A Multi-Scale Approach for the Design of Novel Lubricants
Friction accounts for ~15% of fuel energy losses in conventional vehicles. A deeper understanding of lubrication mechanisms in engineering systems and how to accurately model them is therefore necessary. Atomistic simulations can provide fundamental insights in the fluid behaviour under extreme contact conditions, at a high computational cost. On the other hand, continuum methods, while capable of efficiently solving macroscopic problems, cannot resolve features and flow patterns at the nanometer scale, due to the breakdown of the continuum assumption [1]. In this work, we employ a multi-scale approach that combines continuum and particle-based descriptions for simulating hydrodynamic lubrication systems, while seeking ideal designs of virtual lubricants that maximise load carrying capacity and minimize friction.
Inspired by computational [2] and experimental [3] studies of ionic liquids as lubricants, we emulate their layering behaviour and near-wall solidification [2] on the continuum domain by introducing an inhomogeneous viscosity field in the Navier-Stokes equations. Using an Evolutionary Algorithm, optimal viscosity profiles leading to the minimisation of specific friction are identified. By doing so, a potential improvement in friction performance up to 65% was found for a converging hydrodynamic slider.
The study is then extended to nano-hydrodynamic lubrication using Coarse Grain Molecular Dynamics simulations, which can help in selecting specific molecule typologies featuring the aforementioned viscosity variations - and thus the potential for significant friction reduction - under severely loaded contact conditions.
1. I. Cosden and J. Lukes, Comput. Phys. Commun. 184 (8) (2013)
2. K. Gkagkas, V. Ponnuchamy, M. Dašić, and I. Stanković, Tribol. Int. 113 (2016)
3. J. Qu, D. Bansal, B. Yu, J. Howe, H. Luo, S. Dai, H. Li, P.J. Blau, B. Bunting, G. Mordukhovich and D. Smolenski, ACS Appl. Mater. Interfaces 4 (2) (2012)
Inspired by computational [2] and experimental [3] studies of ionic liquids as lubricants, we emulate their layering behaviour and near-wall solidification [2] on the continuum domain by introducing an inhomogeneous viscosity field in the Navier-Stokes equations. Using an Evolutionary Algorithm, optimal viscosity profiles leading to the minimisation of specific friction are identified. By doing so, a potential improvement in friction performance up to 65% was found for a converging hydrodynamic slider.
The study is then extended to nano-hydrodynamic lubrication using Coarse Grain Molecular Dynamics simulations, which can help in selecting specific molecule typologies featuring the aforementioned viscosity variations - and thus the potential for significant friction reduction - under severely loaded contact conditions.
1. I. Cosden and J. Lukes, Comput. Phys. Commun. 184 (8) (2013)
2. K. Gkagkas, V. Ponnuchamy, M. Dašić, and I. Stanković, Tribol. Int. 113 (2016)
3. J. Qu, D. Bansal, B. Yu, J. Howe, H. Luo, S. Dai, H. Li, P.J. Blau, B. Bunting, G. Mordukhovich and D. Smolenski, ACS Appl. Mater. Interfaces 4 (2) (2012)