Tuesday, 1 November 2005 - 1:00 PM
221c
Brownian Dynamics Simulations of Shear-Induced Migration of DNA Molecules in Dilute Solutions near a Solid Boundary
Chih-Chen Hsieh, University of Michigan, 2300 Hayward St., Ann Arbor, MI 48109, Nobuhiko Watari, Dept. of Computational Science and Engineering., Nagoya University, Furo-cho, Chikusa-ku, Nagoya City, Japan, and Ronald G. Larson, Chemical Engineering, University of Michigan, 2300 Hayward St., Ann Arbor, MI 48109.
Recent experiments show that DNA molecules migrate away from solid boundaries in shear flow, and a depletion layer is formed at the steady state. In channel flows, Jendrejack et al. [J. Chem. Phys., 119, 1165 (2003)] have modeled this phenomenon using Brownian dynamics (BD) simulations of a bead-spring model with full hydrodynamic interaction (HI), where a finite element method was used to obtain the hydrodynamic tensor including the wall effect. While this method is successful, the hydrodynamic tensor must be re-computed for different channel geometry. Here, we propose a modified Rotne-Prager-Yamakawa hydrodynamic interaction tensor to describe the hydrodynamic interaction between two spheres with a wall nearby. This newly developed tensor is suitable for Brownian dynamics simulations because it accounts for both the finite volume of the beads and the effect of the presence of a stationary boundary. The tensor obeys the reciprocity relation that originates from self-adjointness of the Stokes operator, and therefore the ad hoc average used to enforce this reciprocity relation in earlier approximations can be avoided. As an initial step, BD simulations of a dumbbell showed that our method yields results similar to those obtained from a kinetic theory for dumbbells near a wall in the presence of shear [Jendrejack et al., J. Chem. Phys., 120, 2513 (2004)]. Finally, We carry out Brownian dynamics simulations with multiple beads and compare the predictions with the experimental configurations and concentrations of DNA molecules in shear flow near a surface reported by Fang et al. [J. Rheology, 49, 127(2005)].
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