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Title: Computer simulation of complex fluids using dissipative particle dynamics
Author: Jury, Simon Ian
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1999
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A parallel code has been developed to implement the Dissipative Particle Dynamics (DPD) simulation algorithm. DPD is a particle based method which simulates the fluid at a mesoscopic scale. Since the DPD interactions are both soft (compared to the potentials used in molecular dynamics) and momentum conserving, DPD offers the possibility of reproducing hydrodynamic behaviour at large length and time scales. Other techniques for hydrodynamic flow simulation are reviewed before the DPD algorithm is presented together with some of the coding issues arising from using a parallel implementation. Equilibrium thermodynamics, as pertaining to phase separation, is presented, together with the scaling arguments used to derive growth laws for domain size. An in depth study of domain size scaling in three dimensional binary fluid phase separation has been completed. For an appropriate choice of parameters, domain growth is shown to enter a regime dominated by capillary and viscous forces. Qualitative analysis of interface maps and velocity fields reveal the Siggia mechanism for domain coarsening in operation. By performing simulations over two orders of magnitude in reduced length and reduced time units, a small yet significant breakdown of scaling is observed in the domain growth rate. Possible explanations for this breakdown are considered. By extending the code, we study a dense solution of an amphiphilic species focusing on the smectic mesophase. Results are presented for the formation of monodomain, bidomain and polydomain lamellar phases. Shearing is performed, using Lees Edwards boundary conditions, the effect of shear on the lamellar phase is examined. It is shown how, for certain concentrations and shear rates, a lamellar structure will tend to fold in upon itself, this is a possible first stage in onion formation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available