3D Numerical Simulation of Turbulent Open-channel Flow Through Vegetation

3D Numerical Simulation of Turbulent Open-channel Flow Through Vegetation
Author: Su Jin Kim
Publisher:
Total Pages:
Release: 2011
Genre: Computational fluid dynamics
ISBN:

A comprehensive understanding of the hydrodynamics in vegetated open-channels and flow-vegetation interaction is of high interest to researchers and practitioners alike for instance in the content of river and coastal restoration schemes. The focus of this study was to investigate the effect of the presence of vegetation on flow resistance, turbulence statistics, and the instantaneous flow in open channels by performing three-dimensional computational-fluid-dynamics (CFD) simulations.

Direct Numerical Simulation of Turbulent Flow Over a Backward-facing Step

Direct Numerical Simulation of Turbulent Flow Over a Backward-facing Step
Author: Michal Andrzej Kopera
Publisher:
Total Pages:
Release: 2011
Genre:
ISBN:

A three-dimensional, turbulent flow in a channel with a sudden expansion was studied by direct numerical simulation of the incompressible Navier-Stokes equations. The objective of this study was to provide statistical data of backwardfacing step flow for turbulence modelling. Additionally, analysis of the statistical and dynamical properties of the flow is performed. The Reynolds number of the main simulation was Reh = 9000, based on the step height and mean inlet velocity, with the expansion ratio ER = 2:0. The discretisation is performed using the spectral/hp element method with stiffly-stable velocity correction scheme for time integration. The inlet boundary condition is a fully turbulent velocity and pressure field regenerated from a plane downstream of the inlet. A constant flowrate was ensured by applying Stokes flow correction in the inlet regeneration area. Time and spanwise averaged results revealed, apart from the primary recirculation bubble, secondary and tertiary corner eddies. Streamlines show an additional small eddy at the downstream tip of the secondary corner eddy, with the same circulation direction as the secondary vortex. The analysis of the 3D, timeonly average shows the wavy spanwise structure of both primary and secondary recirculation bubble, that results in spanwise variations of the mean reattachment location. The visualisation of spanwise averaged pressure uctuations and streamwise velocity showed that the interaction of vortices with the recirculation bubble is responsible for the apping of the reattachment position. The characteristic frequency St = 0:078 was found. The analysis of small-scale energy transfer was performed to reveal large backscatter regions in strong Reynolds stress areas in the mixing layer. High correlation of small-scale transfer with non-linear interaction of large-scale velocity and small-scale vorticity was found. The data of the flow fields was archived. It contains the averages for velocities, pressure and Reynolds stress tensor, as well as 3D instantaneous pressure and velocity history.

Aquananotechnology

Aquananotechnology
Author: David E. Reisner
Publisher: CRC Press
Total Pages: 1370
Release: 2014-09-24
Genre: Science
ISBN: 0415621291

The world’s fresh water supplies are dwindling rapidly—even wastewater is now considered an asset. By 2025, most of the world's population will be facing serious water stresses and shortages. Aquananotechnology: Global Prospects breaks new ground with its informative and innovative introduction of the application of nanotechnology to the remediation of contaminated water for drinking and industrial use. It provides a comprehensive overview, from a global perspective, of the latest research and developments in the use of nanotechnology for water purification and desalination methods. The book also covers approaches to remediation such as high surface area nanoscale media for adsorption of toxic species, UV treatment of pathogens, and regeneration of saturated media with applications in municipal water supplies, produced water from fracking, ballast water, and more. It also discusses membranes, desalination, sensing, engineered polymers, magnetic nanomaterials, electrospun nanofibers, photocatalysis, endocrine disruptors, and Al13 clusters. It explores physics-based phenomena such as subcritical water and cavitation-induced sonoluminescence, and fog harvesting. With contributions from experts in developed and developing countries, including those with severe contamination, such as China, India, and Pakistan, the book’s content spans a wide range of the subject areas that fall under the aquananotechnology banner, either squarely or tangentially. The book strongly emphasizes sorption media, with broad application to a myriad of contaminants—both geogenic and anthropogenic—keeping in mind that it is not enough for water to be potable, it must also be palatable.

Point Source Dispersion in a Direct Numerical Simulation of Turbulent Channel Flow

Point Source Dispersion in a Direct Numerical Simulation of Turbulent Channel Flow
Author: Kostantinos Kontomaris
Publisher:
Total Pages: 494
Release: 1991
Genre:
ISBN:

The dispersion of a scalar quantity from point sources located in a Direct Numerical Simulation of turbulent channel flow is studied. An algorithm for tracking fluid particles or molecular (or thermal) markers is developed and tested. Accurate estimates of a number of Lagrangian characteristics of the flow, necessary for the description of the diffusion process, are reported for the case of a point source in the center of the channel. The consequences of molecular diffusivity on the effectiveness of the turbulence to disperse a foreign substance (or heat) are also explored. A new method is proposed for calculating the effect of Peclet number on the Lagrangian property autocorrelation in isotropic turbulence. Computed property autocorrelations, from a simulated experiment of point source diffusion in the center of the channel, are also reported. Finally, results for the diffusion from point sources located at the channel walls are presented and discussed.

Open-channel Flow Through Simulated Vegetation

Open-channel Flow Through Simulated Vegetation
Author: Fabian Lopez
Publisher:
Total Pages: 0
Release: 1997
Genre: Channels (Hydraulic engineering)
ISBN:

The two equation turbulence model based on the k-epsilon closure scheme was developed to simulate the flow and turbulence characteristics of open-channel flows through nonemergent vegetation. Once the performance of the model was verified, the flow structure of vegetated open channels was numerically simulated. Simulated rigid and flexible plants were used to validate the model. Finally, dimensional analysis allowed identification of the dimensionless parameters that govern suspended sediment transport processes in the presence of vegetation, and thus helped in the design of numerical experiments to investigate the role of different flow properties, sediment characteristics, and vegetation parameters upon the transport capacity.