Spelling suggestions: "subject:"[een] CYLINDER CROSS FLOW"" "subject:"[enn] CYLINDER CROSS FLOW""
1 |
On numerical investigations of flow-induced vibration and heat transfer for flow around cylindersElbanhawy, Amr Yehia Hussein January 2011 (has links)
Vortex shedding is an important mechanism, by which the flow around bluff bodies create forces that excite vibratory motion. Vortex-induced vibration (VIV) is studied for a single circular cylinder by means of Computational Fluid Dynamics (CFD) simulations. An arbitrary Lagrangian Eulerian (ALE) formulation is used to achieve the grid deformation needed for VIV. In this thesis, a multifaceted approach is undertaken by which response dynamics and wake interaction are addressed. Four major aspects are considered in the study: the Reynolds number (Re); the mass and damping; the degree-of-freedom for VIV; and the mutual effect between VIV and heat transfer.As attention is paid towards high pre-critical Re flow, the turbulent flow around the cylinder is treated by two turbulence modelling approaches: unsteady Reynolds Averaged Navier Stokes (uRANS), and Large Eddy Simulation (LES). The wake-VIV interaction is analyzed by looking at mean velocities and Reynolds stresses, where decomposition of flow scales is undertaken to explore the evolution of coherent eddy structures, downstream of the cylinder. Conversely, the VIV response is analyzed by considering oscillation amplitude and frequency, in addition to the excitation and inertial dynamics.High turbulence in the separated shear layers disorders the cylinder's VIV response and induces higher amplitudes. The sensitivity for Re is found more pronounced in cylinders with low mass and damping. Meanwhile, VIV is found to enhance wake mixing, and to significantly change the near wake Reynolds stresses. It is suggested that the increase in Re brings a change to the wake patterns, which are known in VIV at lower Re. The kinetic energy production, of near wake eddy structures, is qualitatively altered with the presence of VIV. Furthermore, the surface heat flux is found to cause a noticeable increase in VIV amplitude, as long as it does not disorder the wake correlation. The cylinder's oscillation increases the average value of the Nusselt number (Nu), while the local variance of Nu rises markedly post-separation.
|
2 |
[pt] CARACTERIZAÇÃO DAS FORÇAS E DO AMORTECIMENTO VISCOSO AGINDO SOBRE AS LINHAS DE CONTROLE DE COMPLETAÇÃO INTELIGENTE / [en] CHARACTERIZATION OF FORCES AND VISCOUS DAMPING ACTION ON INTELLIGENT COMPLETION CONTROL LINESTHIAGO HANDERSON TORRES EDUARDO 28 October 2022 (has links)
[pt] Diante dos cenários de produção cada vez mais desafiadores, a indústria
de petróleo tem sido forçada a expandir os limites operacionais para vazões,
temperaturas e pressões mais elevadas. Como consequência, cenários mais
rigorosos são encontrados, levando à redução da vida útil dos equipamentos
atuais, como por exemplo, a falha prematura por fadiga de linhas de controle
de poços com completação inteligente. Estas linhas encontram-se expostas
ao escoamento turbulento na região anular da coluna de produção, causando
vibrações e tensões suficientemente altas, podendo levar a uma falha prematura
das linhas por fadiga. Para prevenir estes problemas e desenvolver projetos
mais eficientes, é necessário investigar os fenômenos associados a interação da
vibração da linha com os desprendimentos de vórtices do escoamento. Estes
foram modelados utilizando-se a metodologia DDES (Delayed Detached Eddy
Simulation), o que requer alto custo computacional, devido à necessidade de
utilização de pequenos passos de tempo e de espaçamento de malha. Buscando
reduzir o custo computacional para a modelagem do problema, propõe-se,
neste trabalho, tratar de forma desacoplada a análise estrutural e de fluidodinâmica.
As forças atuantes nas linhas de controle no espaço anular do
poço de completação são obtidas desprezando-se a flexibilidade das linhas.
Paralelamente, o fator de amortecimento crítico, necessário para a análise
estrutural da vibração da linha, é obtido através de uma simulação Fluido-
Estrutura de um escoamento cruzado a um cilindro elástico. Os resultados
obtidos mostram que a presente metodologia é promissora, pois permite uma
representação dos fenômenos envolvidos melhor do que a encontrada nos
procedimentos atualmente disponíveis na literatura. / [en] In face of increasingly challenging production scenarios, the oil industry
has been forced to expand operational limits to higher flow rates, temperatures,
and pressures. Therefore, challenging production scenarios are found,
from integrity standpoint, leading to reduction in current equipment life expectancy.
Premature failure of control lines due to fatigue in wells with intelligent
completion is one of the problems that arises from those extreme
conditions. These lines are exposed to turbulent flow in the annular region of
the production string, causing sufficiently high vibrations and stresses. These
dynamic stresses can lead to premature failure of the lines due to fatigue. To
prevent these problems, and to develop more efficient designs, it is necessary
to investigate the phenomena associated with the interaction of the line vibration
with the vortex shedding of the flow. We modeled the phenomena using
the DES (Delayed Detached Eddy Simulation) methodology, which has high
computational cost due to the need of using small time steps and high mesh
refinement. In order to reduce these computational costs, this work proposes
to deal with structural and fluid dynamics analysis in a decoupled way. The
forces acting on the control lines in the annular space of the completion well are
obtained neglecting the flexibility of the lines. In parallel, the critical damping
factor, necessary for the structural vibration analysis of control lines, is
obtained through a Fluid-Structure Interaction (FSI) simulation of an elastic
cylinder subjected to cross flow. The results obtained show that the present
methodology is promising, allowing a better representation of the involved
phenomena, compared to procedures currently available in the literature.
|
Page generated in 0.0402 seconds