Large-Scale Analysis and Local Stress Assessment of Flexible Unbonded Pipes Using FEA

2012 ◽  
Author(s):  
Ben Edmans ◽  
Giulio Alfano ◽  
Hamid Bahai
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Local Stress ◽  
General Purpose ◽  
Operating Conditions ◽  
Global Model ◽  
Scale Analysis ◽  
Analysis Model ◽  
Detailed Model ◽  
Stress Prediction

Lifespan assessment of flexible risers involves the evaluation of fatigue parameters, requiring accurate predictions of stresses and their variation in pipe components. For predicting the effect of complex three-dimensional nonlinear dynamics on component stress histories, multi-scale methods can combine generality of application with computational efficiency. In this paper, we describe the development of a two-scale computational homogenisation procedure linking a coarse-scale analysis model using specialised beam elements, and a detailed stress prediction model consisting of a pipe section with components modelled with shell elements and frictional contact interactions. To use the procedure, the detailed model first functions as a virtual test rig, by which parameters of the global model may be determined. For detailed stress prediction, the global model is tested under the operating conditions of interest providing a set of generalised strains which are applied to the detailed model. The models are implemented in the general-purpose finite-element package Abaqus. As key aspects of the procedure, we show how generalised stresses and strains can be imposed on the detailed model uniformly without introducing spurious boundary effects and demonstrate how local stresses can be determined using strain data from the global model.

Effect of Changing Atmospheric and Operating Conditions on the Thermal Stresses in PV Modules

2012 ◽  
Author(s):  
M. U. Siddiqui ◽  
A. F. M. Arif
Keyword(s):  
Power Systems ◽  
Large Scale ◽  
Thermal Stresses ◽  
Direct Method ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Pv Module ◽  
Battery Chargers ◽  
Pv Modules

Photovoltaic (PV) technology provides a direct method to convert solar energy into electricity. In recent years, the use of PV systems has increased greatly with many applications of PV devices in systems as small as battery chargers to large scale electricity generation systems and satellite power systems. An important factor that influences the reliability of photovoltaic modules is their ability to withstand high thermal stresses which develop in PV modules due to the different coefficients of thermal expansion of the different module materials. PV modules also experience thermal cycles which can lead to failure of the module. In the present work, three dimensional numerical thermal and structural models of a PV module were developed and sequentially coupled together to calculate the temperature distribution in the PV module and the thermal stresses developing in it. The model is also capable of simulating PV module cooling. Using the model, a study was conducted to evaluate the thermal and structural performance of the module with and without cooling and the variation in thermal stress magnitudes with changing environmental conditions (solar radiation and ambient temperature) and operating conditions (heat exchanger inlet temperature and velocity).

Mixing in Large Scale Tanks: Part I — Flow Modeling of Turbulent Mixing Jets

2004 ◽  
Author(s):  
Si Young Lee ◽  
Robert A. Dimenna ◽  
Richard A. Leishear ◽  
David B. Stefanko
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Liquid Level ◽  
Computational Results ◽  
Validation Data ◽  
Flow Measurements ◽  
Three Dimensional Representation ◽  
Lower Elevation ◽  
Tank Geometry

Flow evolution models were developed to evaluate the performance of the new advanced design mixer pump (ADMP) for sludge mixing and removal operations in one of the large-scale Savannah River Site (SRS) waste tanks, Tank 18. This paper is the first in a series of four that describe the computational model and its validation, the experiment facility and the flow measurements used to provide the validation data, the extension of the computational results to real tank conditions through the use of existing sludge suspension data, and finally, the sludge removal results from actual Tank 18 operations using the new ADMP. A computational fluid dynamics (CFD) approach was used to simulate the sludge removal operations. The models employed a three-dimensional representation of the tank with a two-equation turbulence model, since this approach was verified by both test and literature data. The discharge of the ADMP was modeled as oppositely directed hydraulic jets submerged at the center of the 85-ft diameter tank, with pump suction taken from below. The calculations were based on prototypic tank geometry and nominal operating conditions. In the analysis, the magnitude of the local velocity was used as a measure of slurrying and suspension capability. The computational results showed that normal operations in Tank 18 with the ADMP mixer and a 70-in liquid level would provide adequate sludge removal in most regions of the tank. The exception was the region within about 1.2 ft of the tank wall, based on an historical minimum velocity required to suspend sludge. Sensitivity results showed that a higher tank liquid level and a lower elevation of pump nozzle would result in better performance in suspending and removing the sludge. These results were consistent with experimental observations.

scholarly journals Deep Generative Design with 3D Pharmacophoric Constraints

2021 ◽  
Author(s):  
Fergus Imrie ◽  
Thomas E. Hadfield ◽  
Anthony R. Bradley ◽  
Charlotte M. Deane
Keyword(s):  
Design Process ◽  
Large Scale ◽  
Molecular Design ◽  
Structural Information ◽  
Three Dimensional ◽  
General Purpose ◽  
Generative Models ◽  
Base Line ◽  
Lead Optimisation ◽  
3D Representations

AbstractGenerative models have increasingly been proposed as a solution to the molecular design problem. However, it has proved challenging to control the design process or incorporate prior knowledge, limiting their practical use in drug discovery. In particular, generative methods have made limited use of three-dimensional (3D) structural information even though this is critical to binding. This work describes a method to incorporate such information and demonstrates the benefit of doing so. We combine an existing graph-based deep generative model, DeLinker, with a convolutional neural network to utilise physically-meaningful 3D representations of molecules and target pharmacophores. We apply our model, DEVELOP, to both linker and R-group design, demonstrating its suitability for both hit-to-lead and lead optimisation. The 3D pharmacophoric information results in improved generation and allows greater control of the design process. In multiple large-scale evaluations, we show that including 3D pharmacophoric constraints results in substantial improvements in the quality of generated molecules. On a challenging test set derived from PDBbind, our model improves the proportion of generated molecules with high 3D similarity to the original molecule by over 300%. In addition, DEVELOP recovers 10 × more of the original molecules compared to the base-line DeLinker method. Our approach is general-purpose, readily modifiable to alternate 3D representations, and can be incorporated into other generative frameworks. Code is available at https://github.com/oxpig/DEVELOP.

Parallel Analysis of Incompressible Flow and Structure Interaction Using Partitioned Iterative Method

2012 ◽  
Author(s):  
Shunji Kataoka ◽  
Hiroshi Kawai ◽  
Satsuki Minami ◽  
Shinobu Yoshimura
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Analysis Model ◽  
Iterative Coupling ◽  
Structure Interaction ◽  
Large Scale Analysis ◽  
Coupling Approach ◽  
Analysis System ◽  
Partitioned Method ◽  
Partitioned Methods

Dynamic response considering fluid structure interaction (FSI) is crucial in many engineering fields and the numerical methods to solve the FSI problems are keenly demanded in engineering field. Generally coupled phenomena can be simulated in either monolithic or partitioned methods, however the application of FSI analysis are limited because of its calculation costs. The partitioned method is now focused because it can re-use the existing flow and structural analysis solver without elaborated modification and it gives the same accuracy when iterative coupling approach is taken. When the partitioned method combined with the existing flow and structure solver which can solve large-scale analysis model, it is expected to solve realistic three dimensional complex FSI problems in acceptable durations. In this work, the partitioned FSI analysis system are developed using existing flow and structure solvers. The system is applied to several validation models and accuracy and efficiency of the solver are shown.

DrillString Vibration With Hole-Enlarging Tools: Analysis and Avoidance

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Robello Samuel ◽  
Dongping Yao
Keyword(s):  
Vibration Analysis ◽  
Mathematical Formulation ◽  
Three Dimensional ◽  
Technical Conference ◽  
Careful Consideration ◽  
Operating Conditions ◽  
Drilling Process ◽  
Analysis Model ◽  
Incidence Data ◽  
Lateral Displacements

In high-risk, high-cost environments, such as ultra-deep waters, refining advanced technologies for the successful completion of wells is paramount. Challenges are still very much associated with complex bottomhole assemblies (BHAs) and with the vibration of the drillstring when used with hole enlarging tools. These tools with complex profiles and designs become additional excitation sources of vibration. The more widespread use of downhole tools for both directional telemetry and logging-while-drilling (LWD) applications, as part of the front line data acquisition system within the drilling process, has made reliability a prime area of importance. This paper presents and validates an existing model to predict severe damaging vibrations. It also provides analysis techniques and guidelines to successfully avoid the vibration damage to downhole tools and to their associated downhole assemblies when using hole enlarging tools, such as hole openers and underreamers. The dynamic analysis model is based on forced frequency response (FFR) to solve for resonant frequencies. In addition, a mathematical formulation includes viscous, axial, torsional, and structural damping mechanisms. With careful consideration of input parameters and the judicious analysis of results, we demonstrated that drillstring vibration can be avoided by determining the three-dimensional vibrational response at selected excitations that are likely to cause them. In addition, the analysis provides an estimate of relative bending stresses, shear forces, and lateral displacements for the assembly used. Based on the study, severe vibrations causing potentially damaging operating conditions that had been a major problem in nearby wells were avoided. Steps required to estimate the operating range of the drilling parameter such as weight on bit and rotational speeds to mitigate and avoid the downhole tool failures due to vibration are given. Extensive simulations were performed to compare the data from the downhole vibration sensors; this paper includes severe vibration incidence data from three case studies in which the model estimated, predicted, and avoided severe vibration (Samuel, R., et al., 2006, “Vibration Analysis Model Prediction and Avoidance: A Case History,” Paper SPE 102134 Presented at the IADC India Conference, Mumbai, India, Oct. 16–18; Samuel, R., 2010, “Vibration Analysis for Hole Enlarging Tools” SPE 134512, Annual Technical Conference, Florence, Italy).

A Three Dimensional CFD Model for PEMFC

2004 ◽  
Author(s):  
Shaoping Li ◽  
Ulrich Becker
Keyword(s):  
Three Dimensional ◽  
Gas Diffusion ◽  
Heating Time ◽  
General Purpose ◽  
Operating Conditions ◽  
Computational Domain ◽  
Flow Energy ◽  
Modeling Approach ◽  
Catalyst Layers ◽  
Diffusion Layers

A 3-D computational model for PEMFC simulations has been developed and implemented in FLUENT, a general purpose commercial software package with multi-physics capabilities. In this modeling approach, transport equations for flow, energy, species and electro-potentials (both solid and membrane phases) are solved in the entire computational domain that includes current collectors, gas channels, porous gas diffusion layers, reacting catalyst layers and the membrane. Various physical processes such as multi-component diffusion, electro-chemical reactions, membrane water transport, liquid water formation and vaporization are considered. The numerical model is also capable of simulating other physical effects encountered in PEMFC operations such as contact resistance, joule heating, time-varying operating conditions etc. The details of the modeling approach are first presented in this paper. Results of a parametric study are then given, which sheds lights on the dependence of in-situ distributions, such as species concentrations, water content, temperature and current density, on various operating conditions.

Large scale three-dimensional seepage analysis model test and numerical simulation research on undersea tunnel

2016 ◽  
Vol 59 ◽  
pp. 510-520 ◽  
Author(s):  
Shu-cai Li ◽  
Hong-liang Liu ◽  
Li-ping Li ◽  
Qian-qing Zhang ◽  
Kai Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Model Test ◽  
Large Scale ◽  
Three Dimensional ◽  
Analysis Model ◽  
Seepage Analysis ◽  
Simulation Research

scholarly journals Constraining a 3DVAR Radar Data Assimilation System with Large-Scale Analysis to Improve Short-Range Precipitation Forecasts

2016 ◽  
Vol 55 (3) ◽  
pp. 673-690 ◽  
Author(s):  
Eder Paulo Vendrasco ◽  
Juanzhen Sun ◽  
Dirceu Luis Herdies ◽  
Carlos Frederico de Angelis
Keyword(s):  
Data Assimilation ◽  
Short Range ◽  
Large Scale ◽  
Three Dimensional ◽  
Radar Data ◽  
Scale Analysis ◽  
Large Scale Analysis ◽  
Assimilation Process ◽  
The Cost ◽  
Radar Data Assimilation

AbstractIt is known from previous studies that radar data assimilation can improve short-range forecasts of precipitation, mainly when radial wind and reflectivity are available. However, from the authors’ experience radar data assimilation, when using the three-dimensional variational data assimilation (3DVAR) technique, can produce spurious precipitation results and large errors in the position and amount of precipitation. One possible reason for the problem is attributed to the lack of proper balance in the dynamical and microphysical fields. This work attempts to minimize this problem by adding a large-scale analysis constraint in the cost function. The large-scale analysis constraint is defined by the departure of the high-resolution 3DVAR analysis from a coarser-resolution large-scale analysis. It is found that this constraint is able to guide the assimilation process in such a way that the final result still maintains the large-scale pattern, while adding the convective characteristics where radar data are available. As a result, the 3DVAR analysis with the constraint is more accurate when verified against an independent dataset. The performance of this new constraint on improving precipitation forecasts is tested using six convective cases and verified against radar-derived precipitation by employing four skill indices. All of the skill indices show improved forecasts when using the methodology presented in this paper.

scholarly journals Subvisible cirrus clouds – a dynamical system approach

2017 ◽  
Vol 24 (3) ◽  
pp. 307-328 ◽  
Author(s):  
Elisa Johanna Spreitzer ◽  
Manuel Patrik Marschalik ◽  
Peter Spichtinger
Keyword(s):  
Low Temperature ◽  
Differential Equations ◽  
Temperature Regime ◽  
Large Scale ◽  
Cloud Model ◽  
Three Dimensional ◽  
Cirrus Clouds ◽  
Diffusional Growth ◽  
Detailed Model ◽  
Homogeneous Freezing

Abstract. Ice clouds, so-called cirrus clouds, occur very frequently in the tropopause region. A special class are subvisible cirrus clouds with an optical depth lower than 0.03, associated with very low ice crystal number concentrations. The dominant pathway for the formation of these clouds is not known well. It is often assumed that heterogeneous nucleation on solid aerosol particles is the preferred mechanism although homogeneous freezing of aqueous solution droplets might be possible, since these clouds occur in the low-temperature regime T < 235 K. For investigating subvisible cirrus clouds as formed by homogeneous freezing we develop a reduced cloud model from first principles, which is close enough to complex models but is also simple enough for mathematical analysis. The model consists of a three-dimensional set of ordinary differential equations, and includes the relevant processes as ice nucleation, diffusional growth and sedimentation. We study the formation and evolution of subvisible cirrus clouds in the low-temperature regime as driven by slow vertical updraughts (0 < w ≤ 0. 05 m s−1). The model is integrated numerically and also investigated by means of theory of dynamical systems. We found two qualitatively different states for the long-term behaviour of subvisible cirrus clouds. The first state is a stable focus; i.e. the solution of the differential equations performs damped oscillations and asymptotically reaches a constant value as an equilibrium state. The second state is a limit cycle in phase space; i.e. the solution asymptotically approaches a one-dimensional attractor with purely oscillatory behaviour. The transition between the states is characterised by a Hopf bifurcation and is determined by two parameters – vertical updraught velocity and temperature. In both cases, the properties of the simulated clouds agree reasonably well with simulations from a more detailed model, with former analytical studies, and with observations of subvisible cirrus, respectively. The reduced model can also provide qualitative interpretations of simulations with a complex and more detailed model at states close to bifurcation qualitatively. The results indicate that homogeneous nucleation is a possible formation pathway for subvisible cirrus clouds. The results motivate a minimal model for subvisible cirrus clouds (SVCs), which might be used in future work for the development of parameterisations for coarse large-scale models, representing structures of clouds.

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