Using the Medial Axis to Represent Complex Flow Structures for Flow Feature-Aligned Mesh Generation

2013 ◽  
Author(s):  
Matthew Harris ◽  
Ning Qin
Keyword(s):  
Mesh Generation ◽  
Medial Axis ◽  
Flow Structures ◽  
Complex Flow ◽  
Flow Feature

Topological Flow Structures of Annular Swirling Jets

2001 ◽  
Vol 17 (3) ◽  
pp. 131-138
Author(s):  
Feng Chin Tsai ◽  
Rong Fung Huang
Keyword(s):  
Vortex Breakdown ◽  
Swirling Flow ◽  
Single Bubble ◽  
Flow Structures ◽  
Complex Flow ◽  
Swirl Number ◽  
Recirculation Bubble ◽  
Annular Jet ◽  
Ring Mode ◽  
Dual Ring

AbstractThe effects of blockage and swirl on the macro flow structures of the annular jet past a circular disc are experimentally studied through the time-averaged streamline patterns. In the blockage-effect regime, the flows present multiple modes, single bubble, dual rings, vortex breakdown, and triple rings, in different regimes of blockage ratio and swirl number. The topological models of the flow structures are proposed and discussed according to the measured flow fields to manifest the complex flow structures. The single bubble is a closed recirculation bubble with a stagnation point on the central axis. The dual-ring flow is an open-top recirculsation zone, in which a pair of counter-rotating vortex rings exists in the near wake. The fluids in the dual rings are expelled downstream through a central jet-like swirling flow. A vortex breakdown may occur in the central jet-like swirling flow if the exit swirl number exceeds critical values. When the vortex breakdown interacts with the dual rings, a complex triple-ring flow structure forms. Axial distributions of the local swirl number are presented and discussed. The local swirl number increases with the increase of the exit swirl number and attains the maximum in the dual-ring mode. At large exit swirl numbers where the vortex breakdown occurs, the local swirl number decreases drastically to a low value.

Automatic Hex-Dominant Mesh Generation for Complex Flow Configurations

2018 ◽  
Vol 11 (6) ◽  
pp. 615-624
Author(s):  
Nihar Sawant ◽  
Soji Yamakawa ◽  
Satbir Singh ◽  
Kenji Shimada
Keyword(s):  
Mesh Generation ◽  
Complex Flow ◽  
Flow Configurations

scholarly journals Flowtrace: simple visualization of coherent structures in biological fluid flows

2016 ◽  
Author(s):  
William Gilpin ◽  
Vivek N. Prakash ◽  
Manu Prakash
Keyword(s):  
Coherent Structures ◽  
Collective Motion ◽  
Biological Fluid ◽  
Source Code ◽  
Fluid Flows ◽  
Flow Structures ◽  
Time Varying ◽  
Middle Ground ◽  
Complex Flow ◽  
User Intervention

1AbstractWe present a simple, intuitive algorithm for visualizing time-varying flow fields that can reveal complex flow structures with minimal user intervention. We apply this technique to a variety of biological systems, including the swimming currents of invertebrates and the collective motion of swarms of insects. We compare our results to more experimentally-diffcult and mathematically-sophisticated techniques for identifying patterns in fluid flows, and suggest that our tool represents an essential “middle ground” allowing experimentalists to easily determine whether a system exhibits interesting flow patterns and coherent structures without the need to resort to more intensive techniques. In addition to being informative, the visualizations generated by our tool are often striking and elegant, illustrating coherent structures directly from videos without the need for computational overlays. Our tool is available as fully-documented open-source code available for MATLAB, Python, or ImageJ at www.flowtrace.org.

scholarly journals Experimental Research and Numerical Analysis of Flow Phenomena in Discharge Object with Siphon

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3330
Author(s):  
Milan Sedlář ◽  
Pavel Procházka ◽  
Martin Komárek ◽  
Václav Uruba ◽  
Vladislav Skála
Keyword(s):  
Experimental Research ◽  
Turbulence Models ◽  
Free Surface Flow ◽  
Stationary Flow ◽  
Surface Flow ◽  
Flow Structures ◽  
Complex Flow ◽  
Flow Topology ◽  
Image Velocimetry ◽  
Flow Phenomena

This article presents results of the experimental research and numerical simulations of the flow in a pumping system’s discharge object with the welded siphon. The laboratory simplified model was used in the study. Two stationary flow regimes characterized by different volume flow rates and water level heights have been chosen. The study concentrates mainly on the regions below and behind the siphon outlet. The mathematical modelling using advanced turbulence models has been performed. The free-surface flow has been carried out by means of the volume-of-fluid method. The experimental results obtained by the particle image velocimetry method have been used for the mathematical model validation. The evolution and interactions of main flow structures are analyzed using visualizations and the spectral analysis. The presented results show a good agreement of the measured and calculated complex flow topology and give a deep insight into the flow structures below and behind the siphon outlet. The presented methodology and results can increase the applicability and reliability of the numerical tools used for the design of the pump and turbine stations and their optimization with respect to the efficiency, lifetime and environmental demands.

Study of Turbulent Flow Structures of a Practical Steady Engine Head Flow Using Large-Eddy Simulations

2006 ◽  
Vol 128 (6) ◽  
pp. 1181-1191 ◽  
Author(s):  
V. Huijnen ◽  
L. M. T. Somers ◽  
R. S. G. Baert ◽  
L. P. H. de Goey ◽  
C. Olbricht ◽  
...  
Keyword(s):  
Experimental Data ◽  
Decisive Role ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Upstream Region ◽  
Flow Structures ◽  
Complex Flow ◽  
Production Type ◽  
Large Eddy ◽  
Inflow Conditions

The prediction performance of two computational fluid dynamics codes is compared to each other and to experimental data of a complex swirling and tumbling flow in a practical complex configuration. This configuration consists of a flow in a production-type heavy-duty diesel engine head with 130-mm cylinder bore. One unsteady Reynolds-averaged Navier-Stokes (URANS)-based simulation and two large-eddy simulations (LES) with different inflow conditions have been performed with the KIVA-3V code. Two LES with different resolutions have been performed with the FASTEST-3D code. The parallelization of the this code allows for a more resolved mesh compared to the KIVA-3V code. This kind of simulations gives a complete image of the phenomena that occur in such configurations, and therefore represents a valuable contribution to experimental data. The complex flow structures gives rise to an inhomogeneous turbulence distribution. Such inhomogeneous behavior of the turbulence is well captured by the LES, but naturally damped by the URANS simulation. In the LES, it is confirmed that the inflow conditions play a decisive role for all main flow features. When no particular treatment of the flow through the runners can be made, the best results are achieved by computing a large part of the upstream region, once performed with the FASTEST-3D code. If the inflow conditions are tuned, all main complex flow structures are also recovered by KIVA-3V. The application of upwinding schemes in both codes is in this respect not crucial.

scholarly journals Numerical Analysis of Flow Phenomena in Discharge Object with Siphon Using Lattice Boltzmann Method and CFD

Mathematics ◽  
2021 ◽  
Vol 9 (15) ◽  
pp. 1734
Author(s):  
Jiří Fürst ◽  
Tomáš Halada ◽  
Milan Sedlář ◽  
Tomáš Krátký ◽  
Pavel Procházka ◽  
...  
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Free Water ◽  
Turbulence Models ◽  
Stationary Flow ◽  
Volume Of Fluid ◽  
Surface Flow ◽  
Flow Structures ◽  
Complex Flow ◽  
Boltzmann Method

This article presents numerical simulation of flow in the discharge object with the welded siphon and the free water level. The main numerical tool used in this study is the lattice Boltzmann method combined with the Volume-of-Fluid approach and the Smagorinski LES model. Some aspects of the numerical method are discussed, especially the formulation of the outlet boundary condition. The simulations are carried out with in-house software based on the open-source Palabos framework. Presented results are compared with the CFD simulations, based on the ANSYS CFX software applying the SST and SAS turbulence models and the free-surface flow modeling by means of the Volume-of-Fluid method. The evolution and interactions of main flow structures are analyzed using visualizations and the spectral analysis. All numerical simulations are verified by the experimental data obtained in the hydraulic laboratory with water circuit. A stationary flow regime has been visualized by means of PIV. Both the vertical planes and horizontal planes have been examined, focused mainly on the regions below and behind the siphon outlet. The results show a good agreement of calculated and measured complex flow structures, including time-averaged and instantaneous flow fields.

Finite-Element Modeling of the Hemodynamics of Stented Aneurysms

2004 ◽  
Vol 126 (3) ◽  
pp. 382-387 ◽  
Author(s):  
Gordan R. Stuhne and ◽  
David A. Steinman
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Mesh Generation ◽  
Large Scale ◽  
Side Wall ◽  
Computer Assisted ◽  
Wire Radius ◽  
Complex Flow ◽  
Wall Shear ◽  
Mesh Convergence

Background. Computational fluid dynamics (CFD) simulations are used to analyze the wall shear stress distribution and flow streamlines near the throat of a stented basilar side-wall aneurysm. Previous studies of stented aneurysm flows used low mesh resolution, did not include mesh convergence analyses, and depended upon conformal meshing techniques that apply only to very artificial stent geometries. Method of Approach. We utilize general-purpose computer assisted design and unstructured mesh generation tools that apply in principle to stents and vasculature of arbitrary complexity. A mesh convergence analysis for stented steady flow is performed, varying node spacing near the stent. Physiologically realistic pulsatile simulations are then performed using the converged mesh. Results. Artifact-free resolution of the wall shear stress field on stent wires requires a node spacing of approximately 1/3 wire radius. Large-scale flow features tied to the velocity field are, however, captured at coarser resolution (nodes spaced by about one wire radius or more). Conclusions. Results are consistent with previous work, but our methods yield more detailed insights into the complex flow dynamics. However, routine applications of CFD to anatomically realistic cases still depend upon further development of dedicated algorithms, most crucially to handle geometry definition and mesh generation for complicated stent deployments.

Evidence of complex flow structures in a converging-diverging nozzle caused by a recessed step at the nozzle throat

2015 ◽  
Author(s):  
Margherita Carmine ◽  
Renata Cheli ◽  
Fabio Cozzi ◽  
Andrea Spinelli ◽  
Marta Zocca ◽  
...  
Keyword(s):  
Flow Structures ◽  
Complex Flow ◽  
Nozzle Throat

Numerical simulation of shock wave/tip leakage vortex interaction for a transonic axial fan rotor

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yan Xue ◽  
Ning Ge
Keyword(s):  
Shock Wave ◽  
Vortex Breakdown ◽  
Flow Region ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Flow Structures ◽  
Axial Fan ◽  
Complex Flow ◽  
Vortex Stability ◽  
Theoretical Criterion

Abstract This paper presents the steady numerical investigation on SW/TLV interaction with SST turbulence model at two characteristic operating conditions for a transonic fan rotor, NASA Rotor 67. The main purpose of the present work is to reveal the main flow structures and properties during the SW/TLV interaction, and a theoretical criterion for vortex stability is engineeringly utilized to determine such shock wave-induced vortex stability. The validations for all numerical schemes have been conducted by comparing the RANS solutions with detailed experimental data before the analyses of flow phenomenon and mechanism. The simulation results indicate that numerical methods used in NUAA-Turbo 2.0 solver, independently developed by our team, enable to accurately capture the complex flow structures including shock wave and vortex systems within the blade passages, especially in the tip region. Similar to wing-tip vortex created by vortex generator, the TLV has the same wake-type characteristics. The flow pattern generated by such interaction is characterized by the bulged-forward shock front followed by a subsonic flow region and a slight expansion of vortex core. No apparent vortex breakdown was examined by both intuitive visualization of three-dimensional vortex structure and a theoretical criterion.

Sign in / Sign up

Export Citation Format

Share Document