scholarly journals CFD Modeling of Multiphase Flow in an SKS Furnace with New Tuyere Arrangements

2021 ◽  
Author(s):  
Kezhou Song ◽  
Ari Jokilaakso
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Gas Flow ◽  
Model Simulation ◽  
Gas Injection ◽  
Side Wall ◽  
Copper Smelting ◽  
Cfd Modeling ◽  
Injection Speed ◽  
Wall Shear

AbstractThere has been a great deal of focus on the optimization of tuyere arrangements in SKS bottom blown copper smelting furnaces since the last decade, as the improved furnace operation efficiency of SKS technology has potential that cannot be ignored. New –x + 0 + x deg tuyere arrangements with 14 tuyeres are proposed in this research paper. Using a previously verified numerical model, CFD tests on the velocity distribution and wall shear stress for scaled-down SKS furnace models were conducted, with a constant total volumetric gas flow rate, and different operating parameters and furnace cross-section geometries. The results indicate that, at a relatively low gas injection speed compared with the previously optimized tuyere arrangement, although the –x +0 +x deg tuyere arrangements are unable to supply enhanced agitation in the typical round furnaces, they achieve better performance in elliptical furnaces. At a comparatively higher gas injection speed, the – x + 0 + x deg tuyere arrangements can improve the agitation performance in a round furnace while maintaining an acceptable wall shear stress on the bottom and side wall. The agitation enhancement with the − x +0 +x deg tuyere arrangements can essentially be attributed to stronger interactions between bubble plumes and furnace side walls. To further exploit the advantages of the new tuyere arrangements, an optimized tuyere angle was confirmed by a full-scale furnace model simulation.

Image Based CFD Modeling of Coronary Artery Wall Shear Stress and Importance of Patient-Specific Velocity Boundary Conditions

2007 ◽  
Author(s):  
Kevin R. Johnson ◽  
John N. Oshinski
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Spatial Resolution ◽  
Multidetector Ct ◽  
Atherosclerotic Lesion ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Lesion Development ◽  
Wall Shear ◽  
Atherosclerotic Lesion Development

Low and oscillatory arterial wall shear stress (WSS) have been shown to have an effect on many factors implicated in atherosclerotic lesion development. The majority of studies on the relationship between low or oscillating WSS and sites of intimal thickening and early atherosclerotic lesion development are based on in-vitro model studies of flow and WSS distribution. These models are based on average vessel geometries with average flow conditions and compared to average pathology distribution of lesions that may obscure the true relationship between WSS and lesion distribution[1]. Recent techniques have been developed using coronary MR angiography to create patient-specific 3D models along with velocity measurements of blood flow using phase contrast magnetic resonance (PCMR). However, these models may lack adequate spatial resolution for accurate, localized calculation of WSS[2]. Current, state-of-art multidetector CT scanners offer improvements in spatial resolution over MRI for creation of 3D vessel models.

Flow Prediction in Rotating Ducts Using Coriolis-Modified Turbulence Models

1980 ◽  
Vol 102 (4) ◽  
pp. 456-461 ◽  
Author(s):  
J. H. G. Howard ◽  
S. V. Patankar ◽  
R. M. Bordynuik
Keyword(s):  
Shear Stress ◽  
Aspect Ratio ◽  
Wall Shear Stress ◽  
Coriolis Force ◽  
Rectangular Cross Section ◽  
Turbulent Viscosity ◽  
Side Wall ◽  
Turbulence Models ◽  
Measured Velocity ◽  
Wall Shear

A parabolic numerical analysis procedure has been used to predict the flow in a straight, radial rotating channel of rectangular cross-section, chosen as a simple model of an impeller passage. A two equation turbulence model was employed, with alternative modifications, to include the influence of Coriolis force on turbulent kinetic energy. Alternative Coriolis force terms were evaluated by comparisons in a high-aspect-ratio duct with measured velocity, wall shear stress and turbulent viscosity. Secondary velocity predictions were checked with data from a low-aspect-ratio duct where the Coriolis modification of turbulence was found less influential than the secondary flow in the modification of side wall shear stress.

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.

Measurements of Wall Shear Stress in Axial Flow in a Square Lattice Rectangular Rod Bundle

1986 ◽  
Vol 108 (2) ◽  
pp. 166-172 ◽  
Author(s):  
M. Abdelghany ◽  
R. Eichhorn
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Axial Flow ◽  
Side Wall ◽  
Diameter Ratio ◽  
Square Lattice ◽  
Local Shear ◽  
Wall Shear ◽  
Hot Film ◽  
Local Shear Stress

Hot film probe measurements of the distribution of the wall shear stress were made for axial flow along a rectangular 3 × 6 array of rods with a pitch to diameter ratio, P/D = 4/3, and a wall to diameter ratio, W/D = 2/3. Measurements were performed on rods at several locations and on two duct side walls at a position 62 hydraulic diameters from the entrance. Local shear stress maxima occur near the largest subchannel flow areas with the lowest maximum local shear stress on rods nearest the sidewalls. Maximum to the minimum shear stress ratio on an individual rod is largest for the corner rod. Side wall maximum local shear stress occurs in the first wall subchannel. Overall friction factors calculated from the wall shear stress measurements agree with those calculated from pressure drop data.

Fabrication, Oxidation and Characterization of Shark Skin Inspired Riblet Structures as Aerodynamically Optimized High Temperature Coatings for Blades of Aeroengines

2010 ◽  
Author(s):  
Claudia C. Bu¨ttner ◽  
Uwe Schulz
Keyword(s):  
Shear Stress ◽  
High Temperature ◽  
Wall Shear Stress ◽  
Physical Vapor Deposition ◽  
Gas Flow ◽  
Turbine Blades ◽  
Picosecond Laser ◽  
Single Digit ◽  
Structured Surfaces ◽  
Wall Shear

This paper deals with the study of different structuring methods for high temperature nickel alloys, which are used for compressor and turbine blades in aeroengines. The ideal structured surface combines high oxidation resistance with low drag in a hot gas flow. The effect of drag reduction due to riblet structured surfaces was originally inspired by the shark scales, which have a drag reducing riblet structure. Riblets were successfully produced on a NiCoCrAlY coating by picosecond laser treatment. This method is suitable for larger structures within the range of some tens of micrometers. Furthermore, experiments were performed by depositing different materials through polymer and metal masks via electrodeposition and physical vapor deposition. All fabricated structures were oxidized at 900–1100°C for up to 100 h to simulate the temperature conditions in an aeroengine. The resulting shape of the riblets was characterized using scanning electron microscopy. The most accurate structures were obtained by using photolithography with a subsequent electrodeposition of nickel. This method is suited for single digit micrometer structures. The reduction of the wall shear stress was measured in an oil channel. The riblet structures prior to oxidation showed a reduction of the wall shear stress of up to 4.9%.

scholarly journals Effects of size and elasticity on the relation between flow velocity and wall shear stress in side-wall aneurysms: A lattice Boltzmann-based computer simulation study

2019 ◽  
Author(s):  
Haifeng Wang ◽  
Timm Krüger ◽  
Fathollah Varnik
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Velocity ◽  
Lattice Boltzmann ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Side Wall ◽  
Aneurysm Rupture ◽  
Immersed Boundary ◽  
Wall Shear

AbstractBlood flow in an artery is a fluid-structure interaction problem. It is widely accepted that aneurysm formation, enlargement and failure are associated with wall shear stress (WSS) which is exerted by flowing blood on the aneurysmal wall. To date, the combined effect of aneurysm size and wall elasticity on intra-aneurysm (IA) flow characteristics, particularly in the case of side-wall aneurysms, is poorly understood. Here we propose a model of three-dimensional viscous flow in a compliant artery containing an aneurysm by employing the immersed boundary-lattice Boltzmann-finite element method. This model allows to adequately account for the elastic deformation of both the blood vessel and aneurysm walls. Using this model, we perform a detailed investigation of the flow through aneurysm under different conditions with a focus on the parameters which may influence the wall shear stress. Most importantly, it is shown in this work that the use of flow velocity as a proxy for wall shear stress is well justified only in those sections of the vessel which are close to the ideal cylindrical geometry. Within the aneurysm domain, however, the correlation between wall shear stress and flow velocity is largely lost due to the complexity of the geometry and the resulting flow pattern. Moreover, the correlations weaken further with the phase shift between flow velocity and transmural pressure. These findings have important implications for medical applications since wall shear stress is believed to play a crucial role in aneurysm rupture.

scholarly journals Hemodynamic impingement and the initiation of intracranial side-wall aneurysms

2018 ◽  
Vol 24 (3) ◽  
pp. 288-296 ◽  
Author(s):  
Gerald J Riccardello ◽  
Abhinav R Changa ◽  
Fawaz Al-Mufti ◽  
I Paul Singh ◽  
Chirag Gandhi ◽  
...  
Keyword(s):  
Shear Stress ◽  
Carotid Artery ◽  
Wall Shear Stress ◽  
Internal Carotid Artery ◽  
Secondary Flow ◽  
Internal Carotid ◽  
Fluid Dynamic ◽  
Side Wall ◽  
Flow Patterns ◽  
Wall Shear

Objective The natural history intracranial aneurysms (IA) remains poorly understood despite significant morbidity and mortality associated with IA rupture. Hemodynamic impingement resulting in elevations in wall shear stress and wall shear stress gradient (WSSG) has been shown to induce aneurysmal remodeling at arterial bifurcations. We investigate the hemodynamic environment specific to side-wall pre-aneurysmal vasculature. We hypothesize that fluid impingement and secondary flow patterns play a role in side-wall aneurysm initiation. Methods Eight side-wall internal carotid artery aneurysms from the Aneurisk repository were identified. Pre-aneurysmal vasculature was algorithmically reconstructed. Blood flow was simulated with computational fluid dynamic simulations. An indicator of isolated fluid impingement energy was developed by insetting the vessel surface and calculating the impinging component of the fluid dynamic pressure. Results Isolated fluid impingement was found to be elevated in the area of aneurysm initiation in 8/8 cases. The underlying fluid flow for each area of initiation was found to harbor secondary flow patterns known as Dean’s vortices, the result of changes in momentum imparted by bends in the internal carotid artery (ICA). Conclusion Isolated fluid impingement and secondary flow patterns may play a major role in the initiation of side-wall aneurysm initiation. We are unable to determine if this role is through direct or indirect mechanisms but hypothesize that elevations in isolated fluid impingement mark areas of cerebral vasculature that are at risk for aneurysm initiation. Thus, this indicator provides vascular locations to focus future study of side-wall aneurysm initiation.

Inter-Operator Segmentation Differences Impact Wall Shear Stress Distributions in Patient-Specific Computational Fluid Dynamic Models

2009 ◽  
Author(s):  
Ian C. Campbell ◽  
William W. Sprague ◽  
Marina Piccinelli ◽  
Alessandro Veneziani ◽  
John N. Oshinski
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Dynamic Models ◽  
Fluid Dynamic ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Wall Thickening ◽  
Cross Sectional ◽  
Wall Shear

The link between hemodynamic forces, notably wall shear stress (WSS), and atherogenesis is well established. Patient-specific computational fluid dynamics (CFD) modeling of human vasculature has attracted recent attention because it allows investigators to determine areas at risk for plaque formation and subsequent rupture [1]. Non-invasive in vivo imaging methods such as magnetic resonance (MR) angiography allow acquisition of vascular geometry and cross-sectional velocity such that a CFD model can determine the spatial distribution of WSS. WSS may then be correlated with phenomena such as wall thickening.

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