D. Kasiteropoulou

Numerical Modelling and Analysis of Turbulent Flow in an Open Channel with Submerged Vegetation

Turbulent flow in an open channel whose bed is covered with vegetation is studied. Vegetation has been modeled by a series of small diameter rigid cylinders protruded vertically from the channel bed. 3-D computations were performed using the ANSYS-CFX computer program which uses a finite volume method to solve the partial differential equations describing fluid flow. In order to reduce the computational burden, periodic boundary conditions in the direction of the channel axis have been used. The computational domain has been discretized using tetrahedral elements. Six mesh designs were evaluated in order to choose the optimal/suboptimal mesh and ensure that the solution is independent of the mesh used. The mesh finally chosen provides a good balance between the stability of the solution and the flow field resolution. However, achieving mesh-independent solutions for a complex geometry problem, such as the one studied in this work, requires tremendous computational resourses. The connection of the hydrodynamic model to the study of contaminant transport and sedimentation processes in aquatic environments is also discussed.

Study of fluid flow in grooved micro and nano-channels via dissipative particle dynamic: a tool for desalination membrane design

AbstractA number of recent studies strongly suggest that nanostructured materials, such as carbon nanotubes, nanoporous graphene, and zeolites, can form the basis for the fabrication of next generation membranes for reverse osmosis desalination. In the present work, we investigate the influence of the wall roughness and external driving force on the flow pattern and energy losses in nano and microchannel flow through the estimation of the effective velocity slip at solid walls and other macroscopic quantities such as density, velocity, and pressure. The investigation is based on the dissipative particle dynamics simulation method and the flow studies concern flows between parallel plates with the protrusions located at the upper wall. Roughness is modeled by periodically spaced rectangular protruding elements. When compared to the smooth channel case, lower flow velocities are observed in the central part of the channel for all cases studied. This reduction of velocities becomes more pronounced as the pro...

PARTICLE BASED SIMULATION OF FLUID FLOW IN PERIODICALLY GROOVED CHANNELS

The method of Dissipative Particle Dynamics is applied to investigate the effect of the parameters employed to model the presence of periodic rectangular wall roughness on planar nanochannel flow. The parameters considered here include the fluid/wall interactions, the range of interaction of fluid particles and wall particles (cut-off radius), the external applied force and the coarse-graining parameter (number of atoms per DPD particle). Protrusions of upper wall are modeled by periodically spaced rectangular protruding elements. The dependence of flow pattern on protrusion length and the amplitude of these parameters is investigated. The computed macroscopic quantities of practical interest include density, velocity, and pressure fields. Fluid particle localization near the solid wall is affected by the conservative force and the cut-off radius. Fluid velocity reduces as the protrusion length decreases for constant parameters and reduces as both the conservative force and the cutoff radius increases. The pressure is uniform across most of the channel and their pattern near and inside the cavities depend on the protrusion shape, the conservative force and cutoff radius. For the coarse graining parameter, the density and pressure remain almost constant in the core of the channel and their pattern near and inside the cavities depends on the protrusion shape.