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Dissertation/Thesis Abstract

Single particle DPD: Algorithms and applications
by Pan, Wenxiao, Ph.D., Brown University, 2010, 180; 3430206
Abstract (Summary)

This work presents the new single particle dissipative particle dynamics (DPD) model for flows around bluff bodies that are represented by single DPD particles. This model leads to an accurate representation of the hydrodynamics and allows for economical exploration of the properties of complex fluids. The new DPD formulation introduces a shear drag coefficient and a corresponding term in the dissipative force that, along with a rotational force, incorporates non-central shear forces between particles and preserves both linear and angular momenta. First, we simulated several prototype Stokes flows to verify the performance of the proposed formulation. Next, we demonstrated that, in colloidal suspensions, the suspended spherical colloidal particles can effectively be modeled as single DPD particles. In particular, we investigated the rheology, microstructure and shear-induced migration of a monodisperse colloidal suspension in plane shear flows. The simulation results agree well with both experiments and simulations by the Stokesian Dynamics. Then, we developed a new low-dimensional red blood cell (LD-RBC) model based on this single particle DPD algorithm. The LD-RBC model is constructed as a closed-torus-like ring of 10 DPD particles connected by wormlike chain springs combined with bending resistance. The LD-RBC model is able to capture the linear and non-linear elastic deformations for healthy and malaria-infected cells. Also, it reproduces the key features of blood flow in vessels such as the cell free layer, the Fahraeus effect and the Fahraeus-Lindqvist effect, except for capillaries of sizes comparable to the cell diameter. The discrepancy is caused by the simplified representation of the RBC 3D structure, which becomes more critical for blood flow in small tubes. Finally, we examined the effect of aggregation of RBCs on the blood rheology. To reproduce the tendency of RBCs to form structures known as “rouleaux”, a weak anisotropic attractive interaction derived from the Morse potential is included with each RBC. A reversible rouleau formation is reproduced. The presence of rouleaux causes a great increase in the low-shear-rate viscosity of the suspensions, and a non-zero yield stress. Both are consistent with experimental studies.

Indexing (document details)
Advisor: Karniadakis, George Em
School: Brown University
School Location: United States -- Rhode Island
Source: DAI-B 71/11, Dissertation Abstracts International
Subjects: Applied Mathematics, Mathematics, Particle physics
Keywords: Bluff bodies, DPD, Flows, Monodisperse colloidal suspension, Rouleaux, Shear-induced migration, Single particle
Publication Number: 3430206
ISBN: 978-1-124-30221-8
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