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Rheological And Structural Studies Of Linear Polyethylene Melts Under Planar Elongational Flow Using Nonequilibrium Molecular Dynamics Simulations, David J. Keffer, C. Baig, B. J. Edwards, H. D. Cochran, V. A. Harmandaris
Rheological And Structural Studies Of Linear Polyethylene Melts Under Planar Elongational Flow Using Nonequilibrium Molecular Dynamics Simulations, David J. Keffer, C. Baig, B. J. Edwards, H. D. Cochran, V. A. Harmandaris
Faculty Publications and Other Works -- Chemical and Biomolecular Engineering
We present various rheological and structural properties of three polyethylene liquids, C50H102, C78H158, and C128H258, using nonequilibrium molecular dynamics simulations of planar elongational flow. All three melts display tension-thinning behavior of both elongational viscosities, η1 and η2. This tension thinning appears to follow the power law with respect to the elongation rate, i.e., η ∼ Eb, where the exponent b is shown to be approximately −0.4 for η1 and η2. More specifically, b of η1 is shown to be …
A Validation Of The P-Sllod Equations Of Motion For Homogeneous Steady-State Flows, David J. Keffer, B. J. Edwards, C. Baig
A Validation Of The P-Sllod Equations Of Motion For Homogeneous Steady-State Flows, David J. Keffer, B. J. Edwards, C. Baig
Faculty Publications and Other Works -- Chemical and Biomolecular Engineering
A validation of the p-SLLOD equations of motion for nonequilibrium molecular dynamics simulation under homogeneous steady-state flow is presented. We demonstrate that these equations generate the correct center-of-mass trajectory of the system, are completely compatible with (and derivable from) Hamiltonian dynamics, satisfy an appropriate energy balance, and require no fictitious external force to generate the required homogeneous flow. It is also shown that no rigorous derivation of the SLLOD equations exists to date.
A Comparison Of Simple Rheological Models And Simulation Data Of N-Hexadecane Under Shear And Elongational Flows, David J. Keffer, C. Baig, B. Jiang, B. J. Edwards, H. D. Cochran
A Comparison Of Simple Rheological Models And Simulation Data Of N-Hexadecane Under Shear And Elongational Flows, David J. Keffer, C. Baig, B. Jiang, B. J. Edwards, H. D. Cochran
Faculty Publications and Other Works -- Chemical and Biomolecular Engineering
The microscopic origins of five rheological models are investigated by comparing their predictions for the conformation tensor and stress tensor with the same tensors obtained via nonequilibrium molecular dynamics simulations for n-hexadecane. Steady-state simulations were performed under both planar Couette and planar elongational flows, and the results of each are compared with rheological model predictions in the same flows, without any fitting parameters where possible. The use of the conformation tensor for comparisons between theory and experiment/simulation, rather than just the stress tensor, allows additional information to be obtained regarding the physical basis of each model examined herein. The character …