Stent-Induced Vascular Remodeling in Two-Step Stent-Assisted Coiling Treatment of Brain Aneurysms: A Closer Look Into the Hemodynamic Changes During the Stent Healing Period

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Gabriel B. Santos ◽  
Iago Oliveira ◽  
José L. Gasche ◽  
Julio Militzer ◽  
Carlos E. Baccin
Keyword(s):  
Vascular Remodeling ◽  
Treatment Process ◽  
Geometric Analysis ◽  
Cfd Analysis ◽  
The Novel ◽  
Hemodynamic Changes ◽  
Stent Deployment ◽  
Healing Period ◽  
Treatment Stage ◽  
Computational Fluid Dynamics Cfd

Abstract Stenting has become an important adjunctive tool for assisting coil embolization in complex-shaped intracranial aneurysms. However, as a secondary effect, stent deployment has been related to both immediate and delayed remodeling of the local vasculature. Recent studies have demonstrated that this phenomenon may assume different roles depending on the treatment stage. However, the extent of such event on the intra-aneurysmal hemodynamics is still unclear; especially when performing two-step stent-assisted coiling (SAC). Therefore, we performed computational fluid dynamics (CFD) analysis of the blood flow in four bifurcation aneurysms focusing on the stent healing period found in SAC as a two-step maneuver. Our results show that by changing the local vasculature, the intra-aneurysmal hemodynamics changes considerably. However, even though changes do occur, they were not consistent among the cases. Furthermore, by changing the local vasculature not only the shear levels change but also the shear distribution on the aneurysm surface. Additionally, a geometric analysis alone can mislead the estimation of the novel hemodynamic environment after vascular remodeling, especially in the presence of mixing streams. Therefore, although the novel local vasculature might induce an improved hemodynamic environment, it is also plausible to expect that adverse hemodynamic conditions might occur. This could pose a particularly delicate condition since the aneurysm surface remains completely exposed to the novel hemodynamic environment during the stent healing period. Finally, our study emphasizes that vascular remodeling should be considered when assessing the hemodynamics in aneurysms treated with stents, especially when evaluating the earlier stages of the treatment process.

scholarly journals Influence of different computational approaches for stent deployment on cerebral aneurysm haemodynamics

2011 ◽  
Vol 1 (3) ◽  
pp. 338-348 ◽  
Author(s):  
Annarita Bernardini ◽  
Ignacio Larrabide ◽  
Hernán G. Morales ◽  
Giancarlo Pennati ◽  
Lorenza Petrini ◽  
...  
Keyword(s):  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Cfd Analysis ◽  
Clinical Workflow ◽  
Stent Deployment ◽  
Cerebral Vessel ◽  
Virtual Tools ◽  
Computational Fluid Dynamics Cfd ◽  
Vessel Material ◽  
Set Up

Cerebral aneurysms are abnormal focal dilatations of artery walls. The interest in virtual tools to help clinicians to value the effectiveness of different procedures for cerebral aneurysm treatment is constantly growing. This study is focused on the analysis of the influence of different stent deployment approaches on intra-aneurysmal haemodynamics using computational fluid dynamics (CFD). A self-expanding stent was deployed in an idealized aneurysmatic cerebral vessel in two initial positions. Different cases characterized by a progression of simplifications on stent modelling (geometry and material) and vessel material properties were set up, using finite element and fast virtual stenting methods. Then, CFD analysis was performed for untreated and stented vessels. Haemodynamic parameters were analysed qualitatively and quantitatively, comparing the cases and the two initial positions. All the cases predicted a reduction of average wall shear stress and average velocity of almost 50 per cent after stent deployment for both initial positions. Results highlighted that, although some differences in calculated parameters existed across the cases based on the modelling simplifications, all the approaches described the most important effects on intra-aneurysmal haemodynamics. Hence, simpler and faster modelling approaches could be included in clinical workflow and, despite the adopted simplifications, support clinicians in the treatment planning.

Design Analysis of the Volumatic: A CFD and Experimental Study

2002 ◽  
Author(s):  
Vahid Jalili ◽  
Mayur K. Patel ◽  
Christopher Bailey ◽  
Steve Begg ◽  
Henk Versteeg ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Study ◽  
Laser Doppler Anemometry ◽  
Cfd Analysis ◽  
The Novel ◽  
Initial Part ◽  
Cfd Model ◽  
Novel Approach ◽  
Computational Fluid Dynamics Cfd ◽  
Visualization Techniques

The aim of this paper has been to describe the novel approach adopted in studying the flow field within the Volumatic. In this study a combination of engineering tools such as Computational Fluid Dynamics (CFD), Laser Doppler Anemometry (LDA) and Flow visualization techniques have been employed. The initial part of the study involved the use of CFD in modelling the drug entering the Volumatic. The CFD model was then validated against measurements made using LDA. The agreement obtained was very good; this was particularly encouraging as the CFD analysis was carried out some six months prior to the experimental study.

scholarly journals Design and Numerical Study of the Novel Manifold Header for the Evacuated Tube Solar Collector

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2450
Author(s):  
Martin Beer ◽  
Radim Rybár ◽  
Michal Cehlár ◽  
Sergey Zhironkin ◽  
Peter Sivák
Keyword(s):  
Numerical Study ◽  
Cfd Analysis ◽  
The Novel ◽  
Design Elements ◽  
Serial Connection ◽  
Final Design ◽  
Computational Fluid Dynamics Cfd ◽  
Evacuated Tube ◽  
Prototype Phase ◽  
Selection Of

The presented paper dealt with the concept of an innovative manifold header for evacuated tube solar collectors. The proposed concept eliminates the drawbacks of conventional manifold headers, especially the serial connection of heat pipes that operate under uneven conditions. The advantage of the proposed design of the manifold header is also an increase in the heat exchange surface and the possibility of conducting the heat transfer media flow in a parallel flow arrangement, which increases the overall efficiency. The concept of the manifold header was evaluated on five variations of design with the use of the computational fluid dynamics (CFD) analysis. The results of the CFD analysis confirmed the functionality of the concept and also enabled the selection of the most suitable design elements, which were incorporated into the final design of a manifold header in the pre-prototype phase of manufacturing.

scholarly journals Design of Novel Flash Ironmaking Reactors for Greatly Reduced Energy Consumption and CO2 Emissions

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 332
Author(s):  
Hong Yong Sohn ◽  
De-Qiu Fan ◽  
Amr Abdelghany
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Large Diameter ◽  
Reduction Reaction ◽  
The Novel ◽  
Height Ratio ◽  
Fine Iron ◽  
Computational Fluid Dynamics Cfd ◽  
High Reduction ◽  
Iron Ore Concentrate

The development of a novel ironmaking technology based on fine iron ore concentrate in a flash reactor is summarized. The design of potential industrial reactors for flash ironmaking based on the computational fluid dynamics technique is described. Overall, this simulation work has shown that the size of the reactor used in the novel flash ironmaking technology (FIT) can be quite reasonable vis-à-vis the blast furnaces. A flash reactor of 12 m diameter and 35 m height with a single burner operating at atmospheric pressure would produce 1.0 million tons of iron per year. The height can be further reduced by either using multiple burners, preheating the feed gas, or both. The computational fluid dynamics (CFD)-based design of potential industrial reactors for flash ironmaking pointed to a number of features that should be incorporated. The flow field should be designed in such a way that a larger portion of the reactor is used for the reduction reaction but at the same time excessive collision of particles with the wall must be avoided. Further, a large diameter-to-height ratio that still allows a high reduction degree should be used from the viewpoint of decreased heat loss. This may require the incorporation of multiple burners and solid feeding ports.

Analysis of an Airfoil Using a Transition and Turbulence Model

2016 ◽  
Vol 819 ◽  
pp. 356-360
Author(s):  
Mazharul Islam ◽  
Jiří Fürst ◽  
David Wood ◽  
Farid Nasir Ani
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Turbulence Model ◽  
Original Version ◽  
Transitional Region ◽  
Cfd Analysis ◽  
Computational Fluid Dynamics Cfd

In order to evaluate the performance of airfoils with computational fluid dynamics (CFD) tools, modelling of transitional region in the boundary layer is very critical. Currently, there are several classes of transition-based turbulence model which are based on different methods. Among these, the k-kL- ω, which is a three equation turbulence model, is one of the prominent ones which is based on the concept of laminar kinetic energy. This model is phenomenological and has several advantageous features. Over the years, different researchers have attempted to modify the original version which was proposed by Walter and Cokljat in 2008 to enrich the modelling capability. In this article, a modified form of k-kL-ω transitional turbulence model has been used with the help of OpenFOAM for an investigative CFD analysis of a NACA 4-digit airfoil at range of angles of attack.

An Improved Lifting Line Model for the Design of Marine Propellers

2006 ◽  
Vol 43 (02) ◽  
pp. 100-113
Author(s):  
Fahri Celik ◽  
Mesut Guner
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Cfd Analysis ◽  
Vortex System ◽  
Marine Propellers ◽  
Propeller Design ◽  
Trailing Vortices ◽  
Realistic Representation ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method ◽  
Lifting Line

This paper describes a procedure for the design of marine propellers where more realistic representation of the slipstream shape by the trailing vortex system is taken into account. The slipstream shape behind the propeller is allowed to deform and to align with the direction of local velocity, which is obtained by the sum of the inflow velocity and induced velocities due to the trailing vortices. In classical lifting line approaches, that deformation is neglected. Applications for an autonomous underwater vehicle (AUV) and a fishing vessel are carried out to demonstrate propeller design and the effect of the slipstream contraction. Furthermore, a computational fluid dynamics (CFD) analysis based on the finite volume method and experimental validation of the method are carried out for the propellers. CFD analysis and experimental results are compared with the results obtained from present method.

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