scholarly journals A Hexahedral Mesh Generating Technique for Model Geometry Changing.

2000 ◽  
Vol 66 (646) ◽  
pp. 1096-1102
Author(s):  
Masayuki HARIYA ◽  
Ichirou NISHIGAKI
Keyword(s):  
Hexahedral Mesh ◽  
Model Geometry

scholarly journals A modification of the hexahedral mesh generator based on voxel geometry representation

2020 ◽  
Vol 30 (3) ◽  
pp. 468-479
Author(s):  
A.S. Karavaev ◽  
S.P. Kopysov
Keyword(s):  
Data File ◽  
Initial Position ◽  
General Purpose ◽  
Volume Data ◽  
Hexahedral Mesh ◽  
Mesh Generator ◽  
Surface Patches ◽  
Cad Models ◽  
Sharp Edges ◽  
Model Geometry

We consider a modification of the previously developed voxel-based mesh algorithm to generate models given in STL-geometry format. Proposed hexahedral mesh generator belongs to the family of grid methods, and is general-purpose in terms of a capability to use as source data both volume (voxel) and STL-surface representation of model geometry. For now, the algorithm works with CAD models described in the well-known STL format. However, it also allows to handle higher-order surface patches defined in an arbitrary format if appropriate procedures for projection and intersection operations will be specified. To define the initial position of mesh nodes, a “signed distance field” volume data file, obtained from the STL-geometry, is used. A special projection technique was developed to adapt constructed orthogonal mesh on the model's boundary. It provides an approximation of sharp edges and corners and is performed before running any other operations with the mesh. Finally, to improve the quality of the mesh, additional procedures were implemented, including boundary layers insertion, bad quality cells splitting, and optimization-based smoothing technique. The algorithm has been tested on a sufficient number of models, some of which are given as examples.

scholarly journals Can Multi-threaded Flux Tubes in Coronal Arcades Support a Magnetohydrodynamic Avalanche?

Solar Physics ◽  
2021 ◽  
Vol 296 (8) ◽  
Author(s):  
J. Threlfall ◽  
J. Reid ◽  
A. W. Hood
Keyword(s):  
Magnetic Fields ◽  
Three Dimensional ◽  
Coronal Loops ◽  
Flux Tubes ◽  
Single Thread ◽  
Mhd Instabilities ◽  
Mhd Instability ◽  
Mhd Simulations ◽  
Ideal Mhd ◽  
Model Geometry

AbstractMagnetohydrodynamic (MHD) instabilities allow energy to be released from stressed magnetic fields, commonly modelled in cylindrical flux tubes linking parallel planes, but, more recently, also in curved arcades containing flux tubes with both footpoints in the same photospheric plane. Uncurved cylindrical flux tubes containing multiple individual threads have been shown to be capable of sustaining an MHD avalanche, whereby a single unstable thread can destabilise many. We examine the properties of multi-threaded coronal loops, wherein each thread is created by photospheric driving in a realistic, curved coronal arcade structure (with both footpoints of each thread in the same plane). We use three-dimensional MHD simulations to study the evolution of single- and multi-threaded coronal loops, which become unstable and reconnect, while varying the driving velocity of individual threads. Experiments containing a single thread destabilise in a manner indicative of an ideal MHD instability and consistent with previous examples in the literature. The introduction of additional threads modifies this picture, with aspects of the model geometry and relative driving speeds of individual threads affecting the ability of any thread to destabilise others. In both single- and multi-threaded cases, continuous driving of the remnants of disrupted threads produces secondary, aperiodic bursts of energetic release.

An Automatic Hexahedral Mesh Generation to Control Shape of Elements

2007 ◽  
Vol 43 (4) ◽  
pp. 1505-1508 ◽  
Author(s):  
Hirotomo Fujimori ◽  
So Noguchi ◽  
Hajime Igarashi ◽  
Hideo Yamashita
Keyword(s):  
Mesh Generation ◽  
Hexahedral Mesh ◽  
Hexahedral Mesh Generation

scholarly journals Hexahedral Mesh Generation using the Embedded Voronoi Graph

1999 ◽  
Vol 15 (3) ◽  
pp. 248-262 ◽  
Author(s):  
A. Sheffer ◽  
M. Etzion ◽  
A. Rappoport ◽  
M. Bercovier
Keyword(s):  
Mesh Generation ◽  
Hexahedral Mesh ◽  
Hexahedral Mesh Generation ◽  
Voronoi Graph

Effects of Waves on the Wake of a Surface-Piercing Flat Plate: Experiment and Theory

1993 ◽  
Vol 37 (02) ◽  
pp. 102-118
Author(s):  
F. Stern ◽  
J. E. Choi ◽  
W. S. Hwang
Keyword(s):  
Streamwise Velocity ◽  
Navier Stokes ◽  
Pressure Gradients ◽  
Alternating Direction ◽  
Displacement Thickness ◽  
Acceleration And Deceleration ◽  
Streamwise Velocity Component ◽  
Model Geometry ◽  
Layer Region ◽  
Wave Induced

Results are presented from a towing-tank experiment conducted in order to document the effects of waves on the wake of a surface-piercing body. A unique, simple model geometry is utilized which makes it possible to isolate and identify the most important features of the wave-induced effects. Measurements were made for three wave-steepness conditions: zero, medium, and large. The effects of the waves for the latter two conditions are shown to be significant. In particular, the variations of the external-flow pressure gradients cause acceleration and deceleration phases of the streamwise velocity component and alternating direction of the crossflow, which results in large oscillations of the displacement thickness and wake centerplane velocities as compared to the zero-steepness condition. Remarkably, the wake displays a greater response, that is, a bias with regard to favorable as compared to adverse pressure gradients. The measurements are compared and close agreement is demonstrated with results from Reynolds-averaged Navier-Stokes calculations. Additional calculations are presented, including laminar-flow results, which aid in explicating the characteristics of the near and intermediate wake, the periodic nature of the far wake, and wave-induced separation. Previously, experimental and computational results were presented for the boundary-layer region.

Application of Polyhedral Mesh for Vortex Formation Study for Simple Single Pump Sump

CFD letters ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 13-27
Author(s):  
Mohamad Lutfi Samsudin ◽  
Hasril Hasini
Keyword(s):  
Experimental Data ◽  
Complex Geometry ◽  
Vortex Formation ◽  
Tetrahedral Mesh ◽  
Published Data ◽  
Hexahedral Mesh ◽  
The Past ◽  
Polyhedral Mesh ◽  
Pump Sump ◽  
Comparison Of The Results

Meshing of domain in CFD is an important step to ensure accuracy of the solution. In the past, hexahedral or tetrahedral mesh systems were commonly used, and both have their merits and demerits. For large and complex geometry, polyhedral is another option but its accuracy is claimed to be lacking. In this paper, the use of polyhedral mesh system by past researchers are reviewed. Evaluation on the application of polyhedral mesh system for the study of the vortex formation with a simple single pump sump model is made. Validation was made through the comparison of the results from hexahedral, tetrahedral and polyhedral mesh sizes and the experimental data from published data. The polyhedral mesh system was found to perform satisfactorily and was able to match the results from the hexahedral mesh system as well as the experimental data.

Technical Notes: Solid Model Geometry by Screen Digitizing Images

1991 ◽  
Vol 7 (3) ◽  
pp. 361-363 ◽  
Author(s):  
F. L. Younce ◽  
M. J. Pitts ◽  
G. M. Glenn
Keyword(s):  
Solid Model ◽  
Model Geometry

CFD Analysis of the Combustion Chamber of a Commercial Aircraft Engine of Medium Thrust Class From a Maintenance Perspective

2017 ◽  
Author(s):  
Stefan Kuntzagk ◽  
Jörn Kraft ◽  
Ina Esemann
Keyword(s):  
Combustion Chamber ◽  
Temperature Profile ◽  
Measurement Errors ◽  
Burning Velocity ◽  
Combustion Model ◽  
Cfd Analysis ◽  
Hexahedral Mesh ◽  
Flow Topology ◽  
Geometrical Features ◽  
Exit Temperature

The combustion chamber of aircraft engines plays an important role in achieving the optimum performance during an engine overhaul. For long decades, it has been common understanding in the MRO business that a well overhauled compressor and turbine are required to get an engine with low SFC and high EGT margin. In recent work at Lufthansa Technik AG, a comprehensive CFD analysis of the combustion chamber showed that, in contrast to this, small geometrical features influence the mixing process in the combustion chamber and can have an effect on the exit temperature profile. This in turn can reduce the accuracy of the EGT measurement significantly and create measurement errors and misinterpretations of the real engine performance. In order to get insight into the flow topology, a very detailed digital model has been created using scans of the hardware available in the shop. Important geometrical features such as the cooling provisions and swirl creating components have been included in a very detailed manner with an efficient hexahedral mesh. The model includes the HPT vanes and the cooling flow extraction from the secondary cold flow. CFD results have been generated using the flow solver Ansys CFX 17.1, which is able to predict all relevant physical effects such as injection of liquid fuel, evaporation, and combustion of Jet A1 fuel using the Burning-Velocity combustion model. The flow in the combustion chamber shows large natural fluctuations. Subsequently, for each case a transient calculation has been carried out in order to allow an evaluation of the time-averaged flow field. Different geometrical features are investigated to predict the effect of geometry deviations on the exit temperature profile, e.g. the shape and size of the dilution holes. Finally along the example of two CFM56 engines it will be shown how the data obtained by the detailed CFD model is used to optimize work-scoping and maintenance procedures. On the two cases put forward the combination of extended test-cell instrumentation and detailed modeling enabled not only the identification but also the rectification of combustion chamber deviations. This in turn minimized the necessary work, whereas in the past combustion chamber issues often went unnoticed and consequently resulted in extensive additional work.

Method for Incorporating Three-Dimensional Residual Stresses Into Patient-Specific Simulations of Arteries

2013 ◽  
Author(s):  
David M. Pierce ◽  
Thomas E. Fastl ◽  
Hannah Weisbecker ◽  
Gerhard A. Holzapfel ◽  
Borja Rodriguez-Vila ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Abdominal Aortic ◽  
Model Geometry ◽  
Reconstructed Model

Through progress in medical imaging, image analysis and finite element (FE) meshing tools it is now possible to extract patient-specific geometries from medical images of, e.g., abdominal aortic aneurysms (AAAs), and thus to study clinically relevant problems via FE simulations. Medical imaging is most often performed in vivo, and hence the reconstructed model geometry in the problem of interest will represent the in vivo state, e.g., the AAA at physiological blood pressure. However, classical continuum mechanics and FE methods assume that constitutive models and the corresponding simulations start from an unloaded, stress-free reference condition.

Sign in / Sign up

Export Citation Format

Share Document