Search results for "numerical [Methods]"

Mechanical properties of carbon nanotube fibres: St Venant’s principle at the limit and the role of imperfections

2015

Abstract Carbon nanotube (CNT) fibres, especially if perfect in terms of their purity and alignment, are extremely anisotropic. With their high axial strength but ready slippage between the CNTs, there is utmost difficulty in transferring uniformly any applied force. Finite element analysis is used to predict the stress distribution in CNT fibres loaded by grips attached to their surface, along with the resulting tensile stress–strain curves. This study demonstrates that, in accordance with St Venant’s principle, very considerable length-to-diameter ratios (∼103) are required before the stress becomes uniform across the fibre, even at low strains. It is proposed that lack of perfect orienta…

Global Linear Stability Analysis of the Flow Around a Superhydrophobic Circular Cylinder

2016

International audience; Over the last few years, superhydrophobic (SH) surfaces have been receiving an increasing attention in many scientific areas by virtue of their ability to enhance flow slip past solid walls and reduce the skin-friction drag. In the present study, a global linear-stability analysis is employed to investigate the influence of the SH-induced slip velocity on the primary instability of the 2D flow past a circular cylinder. The flow regions playing the role of 'wavemaker' are identified by considering the structural sensitivity of the unstable mode, thus highlighting the effect of slip on the global instability of the considered flow. In addition, a sensitivity analysis t…

An advanced numerical model for human brain activity investigation

2012

Fluvial eco-hydraulics and morphodynamics: New insights and challenges

2015

The paper concerns the mechanisms underlying the distribution of the bed shear stress in meandering bends. Literature indicates that cross-stream circulation strongly affects the redistribution of the downstream velocity, but the feedback between them is still poorly understood. The aim of this paper is to gain some insight into how the momentum transport by cross-stream circulation contributes to the bed shear stress redistribution. Experimental analysis, based on a detailed dataset collected in a large-amplitude meandering laboratory flume, is presented. From these data an evaluation is made of the terms in the depth-averaged momentum equations and the analysis is especially devoted to te…

A Flux Method for the Numerical Solution of the Stochastic Collection Equation

1998

Abstract A new mass conservative flux method is presented for the numerical solution of the stochastic collection equation. The method consists of a two-step procedure. In the first step the mass distribution of drops with mass x′ that have been newly formed in a collision process is entirely added to grid box k of the numerical grid mesh with xk ⩽ x′ ⩽ xk+1. In the second step a certain fraction of the water mass in grid box k is transported to k + 1. This transport is done by means of an advection procedure. Different numerical test runs are presented in which the proposed method is compared with the Berry–Reinhardt scheme. These tests show a very good agreement between the two approaches…

1-D numerical simulation of sediment transport in alluvial channel beds: study cases

2011

ABSTRACT Quantitative estimate of sediment transport processes is important especially in river-control engineering and for water management projects. In this paper the sediment routing of a 1-D model is presented and applied to some study cases. The procedure simulates the variations of bed roughness conditions due to natural sorting and to generation and migration of bed forms. The suspended-load and the bed-load are treated separately.

Characterisation of submarine groundwater discharge offshore south-eastern Sicily

2005

A complex approach in characterisation of submarine groundwater discharge (SGD) off south-eastern Sicily comprising applications of radioactive and non-radioactive tracers, direct seepage measurements, geophysical surveys and a numerical modelling is presented. SGD fluxes in the Donnalucata boat basin were estimated by direct seepage measurements to be from 4 to 12Ls(-1), which are comparable with the total SGD flux in the basin of 17Ls(-1) obtained from radon measurements. The integrated SGD flux over the Donnalucata coast estimated on the basis of Ra isotopes was around 60m(3)s(-1) per km of the coast. Spatial variations of SGD were observed in the Donnalucata boat basin, the average (222…

Estimación mediante programación genética de los patrones del suelo humectantes para el riego por goteo

2012

Drip irrigation is considered as one of the most efficient irrigation systems. Knowledge of the soil wetted perimeter arising from infiltration of water from drippers is important in the design and management of efficient irrigation systems. To this aim, numerical models can represent a powerful tool to analyze the evolution of the wetting pattern during irrigation, in order to explore drip irrigation management strategies, to set up the duration of irrigation, and finally to optimize water use efficiency. This paper examines the potential of genetic programming (GP) in simulating wetting patterns of drip irrigation. First by considering 12 different soil textures of USDA–SCS soil texture t…

Assessing the performance of thermal inertia and Hydrus models to estimate surface soil water content

2017

The knowledge of soil water content (SWC) dynamics in the upper soil layer is important for several hydrological processes. Due to the difficulty of assessing the spatial and temporal SWC dynamics in the field, some model-based approaches have been proposed during the last decade. The main objective of this work was to assess the performance of two approaches to estimate SWC in the upper soil layer under field conditions: the physically-based thermal inertia and the Hydrus model. Their validity was firstly assessed under controlled laboratory conditions. Thermal inertia was firstly validated in laboratory conditions using the transient line heat source (TLHS) method. Then, it was applied in…

Ecological aspects of plants inhabiting Mediterranean cliffs. Challenges and prospects of life in vertical environments

2021

[ES] Esta tesis investiga las oportunidades, desafíos y limitaciones para la investigación en el campo de la ecología vegetal, en el contexto de los acantilados mediterráneos. En concreto, las especies casmofiticas, cuyos hábitats naturales se caracterizan por su acusada pendiente. Las laderas de las montañas de piedra caliza en la proximidad del mar, en la parte central y occidental del área mediterránea se consideran objetos de estudio. Los estudios se llevaron a cabo en los cinturones costeros de montaña de las costas del noroeste de Sicilia y la costa diánica en la Comunidad Valenciana. El primer capítulo, titulado "The complexity of environmental factors: cliff microclimate", investiga…