Sharif Digital Repository

The aim of this study is to simulate the self-assembly of the surfactant molecules with special chemical structure and bending stiffiness into bilayer membranes using a mesoscopic Dissipative Particle Dynamics (DPD) method. The surfactants are modeled with special chemical structure and bending stiffiness. To confirm that the novel model is physical, we determine the interaction parameters based on matching the compressibility and solubility of the DPD system with real physics of the uid. To match the mutual solubility for binary uids, we use the relation between DPD parameters and x-parameters in Flory-Huggins-type models. Unsaturated bonds can change the stiffiness of a lipid membrane,... 

In this paper, we present an extension of dissipative particle dynamics method in order to study the mixed electroosmotic/pressure-driven micro- or nano-flows. This method is based on the Poisson-Boltzmann equation and has a great potential to resolve the electric double layer (EDL). Hence, apart from studying the bulk flow, it also provides a strong capability in order to resolve the complex phenomena occur inside the EDL. We utilize the proposed method to study the pure electroosmotic and also the mixed electroosmotic/pressure-driven flow through the straight micro-/nano-channels. The obtained results are in good agreement with the available analytical solutions. Furthermore, we study the... 

We use the dissipative particle dynamics (DPD) method to simulate the non-Newtonian electroosmotic flow (EOF) through nanochannels. Contrary to a large amount of past computational efforts dedicated to the study of EOF profile, this work pays attention to the EOF of non-Newtonian fluids, which has been rarely touched in past publications. Practically, there are many MEMS/NEMS devices, in which the EOF behaviour should be treated assuming both non-continuum and non-Newtonian conditions. Therefore, our concern in this work is to simulate the EOF through nanochannels considering both non-Newtonian fluid properties and non-continuum flow conditions. We have chosen DPD as our working tool because... 

In nature, most microorganisms have flexible micro/nanostructure tails, which help them create propulsion, reduce drag, or search for food. Previous studies investigated these flexible structures mostly from the propulsion creation perspective. However, the drag reduction and the underlying physical mechanisms of such tails are less known. This scientific gap is more significant when multi-polymeric/hierarchical structures are used. To fill the gap, we use the dissipative particle dynamics (DPD) method as a powerful fluid-polymer interaction technique to study the flexible tails' influences on drag reduction. Note that the flow regime for these microorganisms is in the range of laminar low... 

The dissipative particle dynamics method is an efficient method for studying the hydrodynamics of complex fluids. One of the most challenging aspects of this method appears when the solid walls exist. The solid walls disturb the homogeneity of the fluid near the wall and cause some spurious fluctuations. Thus, in recent years a large amount of effort has been devoted to solve this shortcoming. Fortunately the mentioned problem has almost been solved for the simple walls such as flat walls, circular cylinders, spheres, etc. However no systematic model has addressed the complex walls. It should be noted that almost all of the walls we deal with in practical problems such as MEMS devices,...