Results for "Numerical modelling" : Scipedia

Monographs of the International Centre for Numerical Methods in Engineering (CIMNE)

Numerical modelling of the growth and remodelling phenomena in biological tissues

Abstract

Living biological tissues are complex structures that have the capacity of evolving
in response to external loads and environmental stimuli. The adequate modelling
of soft biological tissue behaviour is a key issue in successfully reproducing
biomechanical problems through computational analysis.
This study presents a general constitutive formulation capable of representing
the behaviour of these tissues through finite element simulation. It is based on
phenomenological models that, used in combination with the generalized mixing
theory, can numerically reproduce a wide range of material behaviours.
First, the passive behaviour of tissues is characterized by means of hyperelastic
and finite-strain damage models. A generalized damage model is proposed,
providing a flexible and versatile formulation that can reproduce a wide range of
tissue behaviour. It can be particularized to any hyperelastic model and requires
identifying only two material parameters. Then, the use of these constitutive
models with generalized mixing theory in a nite strain framework is described
and tools to account for the anisotropic behaviour of tissues are put forth.
The active behaviour of tissues is characterized through constitutive models
capable of reproducing the growth and remodelling phenomena. These are built
on the hyperelastic and damage formulations described above and, thus, represent
the active extension of the passive tissue behaviour. A growth model considering
biological availability is used and extended to include directional growth. In addition,
a novel constitutive model for homeostatic-driven turnover remodelling is
presented and discussed. This model captures the stiffness recovery that occurs
in healing tissues, understood as a recovery or reversal of damage in the tissue,
which is driven by both mechanical and biochemical stimuli.
Finally, the issue of correctly identifying the material parameters for computational
modelling is addressed. An inverse method using optimization techniques
is developed to facilitate the identification of these parameters.

Abstract

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Monographs of the International Centre for Numerical Methods in Engineering (CIMNE)

Numerical modelling of compressible laminar and turbulent flow. The Cbs algorithm

Abstract

This work is about the development of a general algorithm for the numerical solution of flow equations: the Navier-Stokes set. This set of differential equations models the time dependent behavior of fluids. It is formed by continuity, linear momentum and an energy transport equations. [...]

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Papers Repository of the International Centre for Numerical Methods in Engineering (CIMNE)

Comparative study on sheet metal forming processes by numerical modelling and experiment

Abstract

In this paper some results of a wide experimental program are presented and compared with some finite element solution of sheet metal forming problems using a viscous shell formulation.[...]

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Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería

Hydraulic modeling of combined sewers overflow integrating the results of the SWMM and CFX models.

Abstract

This study proposes a methodology for the calibration of combined sewer overflow (CSO), incorporating the results of the three-dimensional ANSYS CFX model in the SWMM one-dimensional model. The procedure consists of constructing calibration curves in ANSYS CFX that relate the input [...]

51
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Collection of open thesis in transport research

Ground borne vibrations from high speed trains

Abstract

consequence of high speed rail transportation is the generation of elevated ground borne vibrations. This thesis presents several original contributions towards the prediction of these vibrations. Firstly, a new three dimensional finite element model capable of vibration prediction was developed. Its main feature was its ability to model complex track geometries while doing so through a fully coupled vehicle-tracksoil system. Model output was compared to experimental results obtained during this thesis and also to independent data sets. It was shown to predict velocity time histories, vibration frequency spectrums and international vibration descriptors with high accuracy. An appraisal of the suitability of a finite difference time domain modelling approach for railway vibration prediction was also undertaken. This resulted in the development of a new ‘higher order’ perfectly matched layers absorbing boundary condition. This condition was found to offer higher performance in comparison to current alternative absorbing boundary conditions. Field work was then undertaken on high speed lines with varying embankment conditions in Belgium and England. Vibration data was recorded up to 100m from each track and geophysical investigations were performed to determine the underlying soil properties. The results were used for numerical model validation and also to provide new insights into the effect of various embankment conditions on vibration propagation. It was found that embankments generate higher frequency excitation in comparison to nonembankment cases and that cuttings generate higher vibration levels than noncuttings. Once validated the finite element model was used to provide new insights into the effect of train speed, embankment constituent materials and railway track type on vibration levels. It was found that the shape and magnitude of ground vibration increased rapidly as the train’s speed approached the Rayleigh wave speed of the underlying soil. It was also found that ballast, slab and metal tracks produced similar levels of vibration and that stiffer embankments reduced vibration levels at distances near and far from the track. Two vibration mitigation techniques were also explored through numerical simulation. Firstly, an analysis was undertaken to determine the ability of a new modified ballast material to actively isolate vibration within the track structure. Secondly, wave barrier geometries were investigated to optimise their performance whilst minimising cost. It was found that barrier depth was the most influential parameter, whereas width had little effect. Additionally, geometry optimisation was found to result in a 95% cost saving in comparison to a base case. Using a vast array of results generated using the previously developed finite element model, a new empirical prediction model was also developed, capable of quickly assessing vibration levels across large sections of track. Unlike currently available empirical models, it was able to account for soil properties in its calculation and could predict a variety of international vibration metrics. It was shown to offer increased prediction performance in comparison to an alternative empirical model.

Abstract

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Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería

Partially saturation effect on fine sands and earth pressure in a sheetpile wall

Abstract

Generally, the effects of suction in fine sands can be evidenced by a stiffening of the material, as the capillary front advances in the granular skeleton. In geotechnical retention structures this effect can [...]

244
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