Estudo do quebra-mar do Porto de Pesca de Albufeira: modelação numérica do galgamento usando um modelo SPH

Dissertação para obtenção do Grau de Mestre em Engenharia Mecânica

Utilização do Sistema Prolene de Hérnia (SPH) para o reparo de hérnias inguinais

OBJETIVO: Aferir complicações pós-operatórias imediatas e tardias em pacientes portadores de hérnia inguinal, submetidos à correção cirúrgica pela técnica de Gilbert1, com utilização do Sistema Prolene de Hérnia (SPH). MÉTODOS: Foram pesquisados todos os pacientes submetidos à herniorrafia inguinal com tela PHS no Hospital São Lucas da PUCRS no período de janeiro de 2001 até ourubro de 2006. As informações foram coletadas de modo retrospectivo, através de contato telefônico e revisão de prontuários. O protocolo de coleta de dados contemplou os aspectos epidemiológicos, bem como as complicações imediatas e tardias. RESULTADOS: Foram incluídos 96 pacientes. Foram identificadas seis (6,25%) complicações, em pacientes distintos; nenhuma complicação com óbito. Dois pacientes (2,08%) apresentaram seroma; hematoma foi identificado em um paciente (1,04%); um paciente (1,04%) apresentou infecção de ferida operatória. Dois pacientes (2,08%) apresentaram edema escrotal. Após seguimento médio de 49,25 meses (16-86,12) dois pacientes (2,08%) apresentaram dor crônica e um paciente (1,04%) apresentou recorrência, com vinte e seis meses de pós-operatório. CONCLUSÃO: O reparo de hérnias inguinais com tela PHS é um método seguro, eficaz, facilmente reprodutível e com baixas taxas de complicações, recorrência ou sintomas em longo prazo.

SPH simulations of clumps formation by dissipative collisions of molecular clouds - II. Magnetic case

We performed computer simulations of interstellar cloud-cloud collisions using the three-dimensional smoothed particle magnetohydrodynamics method. In order to study the role of the magnetic field on the process of collision-triggered fragmentation, we focused our attention on head-on supersonic collisions between two identical spherical molecular-clouds. Two extreme configurations of the magnetic field were adopted: parallel and perpendicular to the initial clouds motion. The initial magnetic field strength was approximately 12.0 muG. In the parallel case, much more of the collision debris were retained in the shocking region than in the non-magnetic case where gas escaped freely throughout the symmetry plane. Differently from the non-magnetic case, eddy-like vortices were formed. The regions of highest vorticity and the the regions of highest density are offset. We found clumps formation only in the parallel case, however, they were larger, hotter and less dense than in the analogous non-magnetic case. In the perpendicular case, the compressed field works as a magnetic wall, preventing a stronger compression of the colliding clouds. This last effect inhibits direct contact of the two clouds. In both cases, we found that the field lines show a chaotic aspect in large scales. Also, the field magnitude is considerably amplified in the shock layer. However, the field distribution is almost coherent in the higher density regions.

SPH simulations of clumps formation by dissipative collision of molecular clouds - I. Non magnetic case

Computer experiments of interstellar cloud collisions were performed with a new smoothed-particle-hydrodynamics (SPH) code. The SPH quantities were calculated by using spatially adaptive smoothing lengths and the SPH fluid equations of motion were solved by means of a hierarchical multiple time-scale leapfrog. Such a combination of methods allows the code to deal with a large range of hydrodynamic quantities. A careful treatment of gas cooling by H, H(2), CO and H II, as well as a heating mechanism by cosmic rays and by H(2) production on grains surface, were also included in the code. The gas model reproduces approximately the typical environment of dark molecular clouds. The experiments were performed by impinging two dynamically identical spherical clouds onto each other with a relative velocity of 10 km s(-1) but with a different impact parameter for each case. Each object has an initial density profile obeying an r(-1)-law with a cutoff radius of 10 pc and with an initial temperature of 20 K. As a main result, cloud-cloud collision triggers fragmentation but in expense of a large amount of energy dissipated, which occurred in the head-on case only. Off-center collision did not allow remnants to fragment along the considered time (similar to 6 Myr). However, it dissipated a considerable amount of orbital energy. Structures as small as 0.1 pc, with densities of similar to 10(4) cm(-3), were observed in the more energetic collision.

Desenvolvimento de software utilizando a técnica sph (smoothed particle hydrodynamics) na geração de ondas de submersão

Pós-graduação em Engenharia Elétrica - FEIS

Aspectos teórico-numéricos dos métodos SPH e MPS

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Evolución de la transmisión de la energía del oleaje a través de un rompeolas flotante empleando un método SPH

[ES] Debido a la necesidad de proponer estructuras de protección costera que sean ambientalmente viables y operacionalmente efectivas, se propone como estructura para proteger el muelle de la Estación de Guardacostas de Santa Marta, Colombia, un Rompeolas Flotante; empleando para su diseño y validación un modelo en numérico de partículas en 2D, conocido como Smoothed Particle Hydrodynamics. Desarrollando todo el proceso de validación y análisis de los casos para obtener resultados confiables y que permitan proponer un Rompeolas Flotante con dimensiones concretas, que atenúe el efecto del oleaje incidente en el muelle.

Performance Optimization of a Floating Breakwater Model Using SPH Method, with a Practical Application

Máster en Oceanografía

Evaluation of Wave energy transmission through a floating breakwater using the SPH method

[EN]Energy transmission through a box-shaped floating breakwater (FB) is examined, under simplified conditions, by using the smoothed particle hydrodynamics (SPH) method, a mesh-free particle numerical approach. The efficiency of the structure is assessed in terms of the coefficient of transm ission as a function of the wave period and the location of the floating breakwater relative to the zone to be protected. Preliminary results conceming wave energy transmission reveals a clear improvement of the efficiency as wave period decreases andan important role ofthe bathymetry.

SPH calculations of asteroid disruptions: The role of pressure dependent failure models

We present recent improvements of the modeling of the disruption of strength dominated bodies using the Smooth Particle Hydrodynamics (SPH) technique. The improvements include an updated strength model and a friction model, which are successfully tested by a comparison with laboratory experiments. In the modeling of catastrophic disruptions of asteroids, a comparison between old and new strength models shows no significant deviation in the case of targets which are initially non-porous, fully intact and have a homogeneous structure (such as the targets used in the study by Benz and Asphaug, 1999). However, for many cases (e.g. initially partly or fully damaged targets and rubble-pile structures) we find that it is crucial that friction is taken into account and the material has a pressure dependent shear strength. Our investigations of the catastrophic disruption threshold (27, as a function of target properties and target sizes up to a few 100 km show that a fully damaged target modeled without friction has a Q(D)*:, which is significantly (5-10 times) smaller than in the case where friction is included. When the effect of the energy dissipation due to compaction (pore crushing) is taken into account as well, the targets become even stronger (Q(D)*; is increased by a factor of 2-3). On the other hand, cohesion is found to have an negligible effect at large scales and is only important at scales less than or similar to 1 km. Our results show the relative effects of strength, friction and porosity on the outcome of collisions among small (less than or similar to 1000 km) bodies. These results will be used in a future study to improve existing scaling laws for the outcome of collisions (e.g. Leinhardt and Stewart, 2012). (C) 2014 Elsevier Ltd. All rights reserved.

Theoretical Analysis of the No-Slip Boundary Condition Enforcement in SPH Methods

The aim of the present work is to provide an in-depth analysis of the most representative mirroring techniques used in SPH to enforce boundary conditions (BC) along solid profiles. We specifically refer to dummy particles, ghost particles, and Takeda et al. [Prog. Theor. Phys. 92 (1994), 939] boundary integrals. The analysis has been carried out by studying the convergence of the first- and second-order differential operators as the smoothing length (that is, the characteristic length on which relies the SPH interpolation) decreases. These differential operators are of fundamental importance for the computation of the viscous drag and the viscous/diffusive terms in the momentum and energy equations. It has been proved that close to the boundaries some of the mirroring techniques leads to intrinsic inaccuracies in the convergence of the differential operators. A consistent formulation has been derived starting from Takeda et al. boundary integrals (see the above reference). This original formulation allows implementing no-slip boundary conditions consistently in many practical applications as viscous flows and diffusion problems.