scholarly journals Spectroscopic patch model for massive stars using PHOEBE II and FASTWIND

2020 ◽  
Vol 636 ◽  
pp. A59 ◽  
Author(s):  
Michael Abdul-Masih ◽  
Hugues Sana ◽  
Kyle E. Conroy ◽  
Jon Sundqvist ◽  
Andrej Prša ◽  
...  
Keyword(s):  
Massive Stars ◽  
Three Dimensional ◽  
Spherical Geometry ◽  
Analysis Tool ◽  
Line Profiles ◽  
Surface Geometry ◽  
Patch Model ◽  
Spectral Profiles ◽  
Emergent Intensity ◽  
Temperature Surface

Context. Massive stars play an important role in the mechanical and chemical evolution of galaxies. Understanding the internal processes of these stars is vital to our understanding of their evolution and eventual end products. Deformations from spherical geometry are common for massive stars; however, the tools that are currently available for the study of these systems are almost exclusively one-dimensional. Aims. We present a new spectroscopic analysis tool tailored for massive stars that deviate from spherical symmetry. This code (entitled SPAMMS) is a spectroscopic patch model that takes the three-dimensional surface geometry of the system into account to produce spectral profiles at given phases and orientations. Methods. In using the Wilson–Devinney-like code PHOEBE in combination with the nonlocal thermodynamic equilibrium radiative transfer code FASTWIND, we created a three-dimensional mesh that represents the surface geometry of our system and we assigned FASTWIND emergent intensity line profiles to each mesh triangle, which take the local parameters such as temperature, surface gravity, and radius into account. These line profiles were then integrated across the visible surface, where their flux contribution and radial velocity are taken into account, thus returning a final line profile for the visible surface of the system at a given phase. Results. We demonstrate that SPAMMS can accurately reproduce the morphology of observed spectral line profiles for overcontact systems. Additionally, we show how line profiles of rapidly-rotating single stars differ when taking rotational distortion into account, and the effects that these can have on the determined parameters. Finally, we demonstrate the code’s ability to reproduce the Rossiter–Mclaughlin and Struve–Sahade effects.

Multi-Objective Optimization of a Microturbine Compact Recuperator

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Diego Micheli ◽  
Valentino Pediroda ◽  
Stefano Pieri
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Design Procedure ◽  
Domain Size ◽  
Multidisciplinary Optimization ◽  
Computational Domain ◽  
Surface Geometry ◽  
Multi Objective ◽  
Flux Boundary Conditions

An automatic approach for the multi-objective shape optimization of microgas turbine heat exchangers is presented. According to the concept of multidisciplinary optimization, the methodology integrates a CAD parametric model of the heat transfer surfaces, a three-dimensional meshing tool, and a CFD solver, all managed by a design optimization platform. The repetitive pattern of the surface geometry has been exploited to reduce the computational domain size, and the constant flux boundary conditions have been imposed to better suit the real operative conditions. A new approach that couples cold and warm fluids in a periodic unitary cell is introduced. The effectiveness of the numerical procedure was verified comparing the numerical results with available literature data. The optimization objectives are maximizing the heat transfer rate and minimizing both friction factor and heat transfer surface. The paper presents the results of the optimization of a 50kWMGT recuperator. The design procedure can be effectively extended and applied to any industrial heat exchanger application.

An Automated CFD Design and Analysis Tool for Inlet-Bleed Systems

1998 ◽  
Author(s):  
Tom I-P. Shih ◽  
Yu-Liang Lin ◽  
Andrew J. Flores ◽  
Mark A. Stephens ◽  
Mark J. Rimlinger ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Incident Shock ◽  
Navier Stokes ◽  
Oblique Shock Wave ◽  
Design Parameters ◽  
Analysis Tool ◽  
Cfd Analysis ◽  
Circular Holes ◽  
Embedded Grids

Abstract A pre-processor was developed to assist CFD experts and non-experts in performing steady, three-dimensional Navier-Stokes analysis of a class of inlet-bleed problems involving oblique shock-wave/ boundary-layer interactions on a flat plate with bleed into a plenum through rows of circular holes. With this pre-processor, once geometry (e.g., hole dimensions and arrangement) and flow conditions (e.g., Mach number, boundary-layer thickness, incident shock location) are inputted, it will automatically generate every file needed to perform a CFD analysis from the grid system to initial and boundary conditions. This is accomplished by accessing a knowledge base established by experts who understand both CFD and the class of problems being analyzed. For experts in CFD, this tool greatly reduces the amount of time and effort needed to setup a problem for CFD analysis. It also provides experts with knobs to make changes to the setup if desired. For non-experts in CFD, this tool enables reliable and correct usage of CFD. A typical session on a workstation from data input to the generation of all files needed to perform a CFD analysis involves less than ten minutes. This pre-processor, referred to as AUTOMAT-V2, is an improved version of a code called AUTOMAT. Improvements made include: (1) multi-block structured grids can be patched in addition to being overlapped; (2) embedded grids can be introduced near bleed holes to reduce the number of grid points/cells needed by a factor of up to four; (3) grid systems generated allow up to three levels of multigrid; (4) CFL3D is supported in addition to OVERFLOW, two well-known and highly regarded Navier-Stokes solvers developed at NASA’s Langley and Ames Research Centers; (5) all files needed to run RONNIE for patched grids and MAGGIE for overlapped grids are also generated; and (6) more design parameters can be investigated including the study of micro bleed and effects of flow/hole misalignments.

Numerical Simulation on Mooring Performance of LNG-FPSO System in Realistic Seas

2005 ◽  
Author(s):  
Yoshiyuki Inoue ◽  
Md. Kamruzzaman
Keyword(s):  
Time Domain ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Time Domain Analysis ◽  
Analysis Tool ◽  
Motion Response ◽  
Non Linear ◽  
Floating System ◽  
Exciting Forces ◽  
The Time Domain

The LNG-FPSO concept is receiving much attention in recent years, due to its active usage to exploit oil and gas resources. The FPSO offloads LNG to an LNG carrier that is located close to the FPSO, and during this transfer process two large vessels are in close proximity to each other for daylong periods of time. Due to the presence of neighboring vessel, the motion response of both the vessels will be affected significantly. Hydrodynamic interactions related to wave effects may result in unfavorable responses or the risk of collisions in a multi-body floating system. Not only the motion behavior but also the second order drift forces are influenced by the neighboring structures due to interactions of the waves among the structures. A study is made on the time domain analysis to assess the behavior and the operational capability of the FPSO system moored in the sea having an LNG carrier alongside under environmental conditions such as waves, wind and currents. This paper presents an analysis tool to predict the dynamic motion response and non-linear connecting and mooring forces on a parallel-connected LNG-FPSO system due to non-linear exciting forces of wave, wind and current. Simulation for the mooring performance is also investigated. The three-dimensional source-sink technique has been applied to obtain the radiation forces and the transfer function of wave exciting forces on floating multi-bodies. The hydrodynamic interaction effect between the FPSO and the LNG carrier is included to calculate the hydrodynamic forces. For the simulation of a random sea and also for the generation of time depended wind velocity, a fully probabilistic simulation technique has been applied. Wind and current loads are estimated according to OCIMF. The effects of variations in wave, wind and current loads and direction on the slowly varying oscillations of the LNG and FPSO are also investigated in this paper. Finally, some conclusions are drawn based on the numerical results obtained from the present time domain simulations.

Impact of image reconstruction parameters when using 3D DSA reconstructions to measure intracranial aneurysms

2017 ◽  
Vol 10 (3) ◽  
pp. 285-289 ◽  
Author(s):  
Katrina L Ruedinger ◽  
David R Rutkowski ◽  
Sebastian Schafer ◽  
Alejandro Roldán-Alzate ◽  
Erick L Oberstar ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Hounsfield Unit ◽  
Ground Truth ◽  
Individual Case ◽  
Dome Height ◽  
Patient Specific ◽  
Analysis Tool ◽  
Accuracy Of Measurements ◽  
Image Characteristic

Background and purposeSafe and effective use of newly developed devices for aneurysm treatment requires the ability to make accurate measurements in the angiographic suite. Our purpose was to determine the parameters that optimize the geometric accuracy of three-dimensional (3D) vascular reconstructions.MethodsAn in vitro flow model consisting of a peristaltic pump, plastic tubing, and 3D printed patient-specific aneurysm models was used to simulate blood flow in an intracranial aneurysm. Flow rates were adjusted to match values reported in the literature for the internal carotid artery. 3D digital subtraction angiography acquisitions were obtained using a commercially available biplane angiographic system. Reconstructions were done using Edge Enhancement (EE) or Hounsfield Unit (HU) kernels and a Normal or Smooth image characteristic. Reconstructed images were analyzed using the vendor's aneurysm analysis tool. Ground truth measurements were derived from metrological scans of the models with a microCT. Aneurysm volume, surface area, dome height, minimum and maximum ostium diameter were determined for the five models.ResultsIn all cases, measurements made with the EE kernel most closely matched ground truth values. Differences in values derived from reconstructions displayed with Smooth or Normal image characteristics were small and had only little impact on the geometric parameters considered.ConclusionsReconstruction parameters impact the accuracy of measurements made using the aneurysm analysis tool of a commercially available angiographic system. Absolute differences between measurements made using reconstruction parameters determined as optimal in this study were, overall, very small. The significance of these differences, if any, will depend on the details of each individual case.

Geometrical characterisation of fault arrays in three dimensions

2021 ◽  
Author(s):  
Vincent Roche ◽  
Giovanni Camanni ◽  
Conrad Childs ◽  
Tom Manzocchi ◽  
John Walsh ◽  
...  
Keyword(s):  
Full Range ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Normal Faults ◽  
Fault Geometry ◽  
Surface Geometry ◽  
Fault Surface ◽  
Mechanical Stratigraphy ◽  
Quantitative Basis ◽  
Geometry Analysis

<p>Normal faults are often complex three-dimensional structures comprising multiple sub-parallel segments separated by intact or breached relay zones. In this study we outline geometrical characterisations capturing this 3D complexity and providing a semi-quantitative basis for the comparison of faults and for defining the factors controlling their geometrical evolution. Relay zones are classified according to whether they step in the strike or dip direction and whether the relay zone-bounding fault segments are unconnected in 3D or bifurcate from a single surface. Complex fault surface geometry is then described in terms of the relative numbers of different types of relay zones to allow comparison of fault geometry between different faults and different geological settings. A large database of 87 fault arrays compiled primarily from mapping 3D seismic reflection surveys and classified according to this scheme, reveals the diversity of 3D fault geometry. Analysis demonstrates that mapped fault geometries depend on geological controls, primarily the heterogeneity of the faulted sequence and the presence of a pre-existing structure. For example, relay zones with an upward bifurcating geometry are prevalent in faults that reactivate deeper structures, whereas the formation of laterally bifurcating relays is promoted by heterogeneous mechanical stratigraphy. In addition, mapped segmentation depends on resolution limits and biases in fault mapping from seismic data. In particular, the results suggest that the proportion of bifurcating relay zones increases as data resolution increases. Overall, where a significant number of relay zones are mapped on a single fault, a wide variety of relay zone geometries occurs, demonstrating that individual faults can comprise segments that are both bifurcating and unconnected in three dimensions. Models for the geometrical evolution of fault arrays must therefore account for the full range of relay zone geometries that appears to be a characteristic of all faults.</p>

scholarly journals Roughness and Fiber Fraction Dominated Wetting of Electrospun Fiber-Based Porous Meshes

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 34 ◽  
Author(s):  
Piotr Szewczyk ◽  
Daniel Ura ◽  
Sara Metwally ◽  
Joanna Knapczyk-Korczak ◽  
Marcin Gajek ◽  
...  
Keyword(s):  
Contact Angle ◽  
Electrospun Fiber ◽  
Three Dimensional ◽  
Contact Angles ◽  
Electrospun Fibers ◽  
Surface Geometry ◽  
Wetting Contact Angle ◽  
Fiber Fraction ◽  
Significant Difference ◽  
Entrapped Air

Wettability of electrospun fibers is one of the key parameters in the biomedical and filtration industry. Within this comprehensive study of contact angles on three-dimensional (3D) meshes made of electrospun fibers and films, from seven types of polymers, we clearly indicated the importance of roughness analysis. Surface chemistry was analyzed with X-ray photoelectron microscopy (XPS) and it showed no significant difference between fibers and films, confirming that the hydrophobic properties of the surfaces can be enhanced by just roughness without any chemical treatment. The surface geometry was determining factor in wetting contact angle analysis on electrospun meshes. We noted that it was very important how the geometry of electrospun surfaces was validated. The commonly used fiber diameter was not necessarily a convincing parameter unless it was correlated with the surface roughness or fraction of fibers or pores. Importantly, this study provides the guidelines to verify the surface free energy decrease with the fiber fraction for the meshes, to validate the changes in wetting contact angles. Eventually, the analysis suggested that meshes could maintain the entrapped air between fibers, decreasing surface free energies for polymers, which increased the contact angle for liquids with surface tension above the critical Wenzel level to maintain the Cassie-Baxter regime for hydrophobic surfaces.

scholarly journals On the stability of a general magnetic field topology in stellar radiative zones

2019 ◽  
Vol 82 ◽  
pp. 365-371
Author(s):  
K. Augustson ◽  
S. Mathis ◽  
A. Strugarek
Keyword(s):  
Magnetic Field ◽  
Global Change ◽  
Magnetic Fields ◽  
Potential Energy ◽  
Massive Stars ◽  
Spherical Geometry ◽  
Stable Region ◽  
Magnetic Field Topology ◽  
The Stability ◽  
The Magnetic Field

This paper provides a brief overview of the formation of stellar fossil magnetic fields and what potential instabilities may occur given certain configurations of the magnetic field. One such instability is the purely magnetic Tayler instability, which can occur for poloidal, toroidal, and mixed poloidal-toroidal axisymmetric magnetic field configurations. However, most of the magnetic field configurations observed at the surface of massive stars are non-axisymmetric. Thus, extending earlier studies in spherical geometry, we introduce a formulation for the global change in the potential energy contained in a convectively-stable region for both axisymmetric and non-axisymmetric magnetic fields.

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