scholarly journals Interpretation of coronary steal syndrome and haemodynamic changes after surgical closure of coronary fistula using Doppler wire and computational fluid dynamics analysis: a case report

2021 ◽  
Vol 5 (4) ◽  
Author(s):  
Kwan Yong Lee ◽  
Kiyuk Chang ◽  
Joo Myung Lee ◽  
Sang-Wook Lee
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Myocardial Ischaemia ◽  
Cfd Analysis ◽  
Coronary Fistula ◽  
Surgical Closure ◽  
Haemodynamic Changes ◽  
Coronary Steal ◽  
Steal Syndrome

Abstract Background Coronary arteriovenous fistulas (CAFs) are rare but can cause myocardial ischaemia and other complications. However, the haemodynamic and physiologic characteristics of significant CAFs requiring treatment are poorly described. We report a case of CAF causing coronary steal syndrome in which haemodynamic changes were assessed before and after surgical closure using a Doppler wire and computational fluid dynamics (CFD) technique. Case summary A 51-year-old woman presented with exertional chest pain for 3 years. Progressive dyspnoea occurred with exertion. Treadmill and cardiopulmonary exercise tests showed suspicious myocardial ischaemia. Coronary angiography and contrast-enhanced coronary computed tomography angiography (CCTA) revealed a coronary fistula arising from the distal left main coronary artery that drained into the pulmonary artery trunk. We observed a persistent coronary steal phenomenon at baseline and during hyperaemia and a systolic dominant flow rate pattern inside the CAF by Doppler wire-based flow rate measurement. According to CFD analysis based on CCTA, low wall shear stress and a high focal oscillatory shear index were observed at the ostial sites of aneurysmal sacs in the CAF. After successful surgical closure of the CAF, the vessel sizes and flow rate distributions of the coronary arteries increased. Discussion Doppler wire-based flow rate distribution measurements and CFD analysis may facilitate the identification of significant coronary steal syndrome requiring closure and the evaluation of future risks of life-threatening complications such as thrombosis and rupture.

CFD-Analyse zur Leistungssteigerung eines Orbit-Motors*/CFD investigation of the performance of an orbital motor - CFD investigation of the influence of the rotor teeth number and eccentricity on the performance of an orbital motor

2015 ◽  
Vol 105 (06) ◽  
pp. 433-439
Author(s):  
A. Mishev ◽  
T. Stehle
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Volume Fraction ◽  
Cfd Analysis ◽  
Rotor Design ◽  
Pressure Ripple ◽  
Computational Fluid Dynamics Cfd ◽  
Gas Volume Fraction ◽  
Gas Volume

Vorgestellt wird ein neuer Orbit-Motor mit innovativem Rotor-Design. Der Motor wurde grundlegend mit der Methode „Computational Fluid Dynamics (CFD) Analysis“ (numerische Strömungsmechanik) simulativ untersucht und entwickelt. Sechs volle dreidimensionale transiente CFD-Orbit-Motor-Modelle wurden entwickelt und mit dem CFD-Modell eines Standard-Orbit-Motors verglichen. Dabei weisen die CFD-Simulationsergebnisse für die neuen Orbit-Motoren-Modellvarianten einen deutlichen Anstieg des Motordrehmoments sowie wesentlich geringere Druck- und Gasvolumen-Anteil-Pulsationen gegenüber dem Standard-Orbit-Motor auf.   In this paper a new orbital motor with innovative rotor design is presented and fundamentally investigated by means of CFD analysis. Six full 3D transient CFD orbital motor models were designed and compared to a standard orbital motor. The results from the simulation showed a substantial increase of the motor torque and reduction of the pressure ripple and gas volume fraction ripple of all six models. Furthermore the flow rate and the volumetric efficiency of all orbital motor models were predicted.

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.

scholarly journals Theoretical Analysis of Brush Seals Leakage Using Local Computational Fluid Dynamics Estimated Permeability Laws

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Lilas Deville ◽  
Mihai Arghir
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Principal Direction ◽  
Experimental Results ◽  
Leakage Flow ◽  
Cfd Analysis ◽  
Brush Seal ◽  
Brush Seals ◽  
Local Reynolds Number

Brush seals are a mature technology that has generated extensive experimental and theoretical work. Theoretical models range from simple correlations with experimental results to advanced numerical approaches coupling the bristles deformation with the flow in the brush. The present work follows this latter path. The bristles of the brush are deformed by the pressure applied by the flow, by the interference with the rotor and with the back plate. The bristles are modeled as linear beams but a nonlinear numerical algorithm deals with the interferences. The brush with its deformed bristles is then considered as an anisotropic porous medium for the leakage flow. Taking into account, the variation of the permeability with the local geometric and flow conditions represents the originality of the present work. The permeability following the principal directions of the bristles is estimated from computational fluid dynamics (CFD) calculations. A representative number of bristles are selected for each principal direction and the CFD analysis domain is delimited by periodicity and symmetry boundary conditions. The parameters of the CFD analysis are the local Reynolds number and the local porosity estimated from the distance between the bristles. The variations of the permeability are thus deduced for each principal direction and for Reynolds numbers and porosities characteristic for brush seal. The leakage flow rates predicted by the present approach are compared with experimental results from the literature. The results depict also the variations of the pressures, of the local Reynolds number, of the permeability, and of the porosity through the entire brush seal.

scholarly journals Effect of hydraulic and geometric factors upon leakage flow rate in pressurized pipes

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Mayara Francisca da Silva ◽  
Fábio Veríssimo Gonçalves ◽  
Johannes Gérson Janzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Leakage Flow ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Leakage Flow Rate ◽  
Geometric Factors ◽  
Leakage Area ◽  
Computational Fluid Dynamics Cfd

ABSTRACT Computational Fluid Dynamics (CFD) simulations of a leakage in a pressurized pipe were undertaken to determine the empirical effects of hydraulic and geometric factors on the leakage flow rate. The results showed that pressure, leakage area and leakage form, influenced the leakage flow rate significantly, while pipe thickness and mean velocity did not influence the leakage flow rate. With relation to the interactions, the effect of pressure upon leakage flow rate depends on leakage area, being stronger for great leakage areas; the effects of leakage area and pressure on leakage flow rate is more pronounced for longitudinal leakages than for circular leakages. Finally, our results suggest that the equations that predict leakage flow rate in pressurized pipes may need a revision.

Experimentally Validated Computational Fluid Dynamics Model for Data Center With Active Tiles

2018 ◽  
Vol 140 (1) ◽  
Author(s):  
Jayati Athavale ◽  
Yogendra Joshi ◽  
Minami Yoda
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Data Center ◽  
Hot Spot ◽  
Volume Flow Rate ◽  
Optimal Number ◽  
Inlet Temperature ◽  
Cfd Model ◽  
Level Model

Abstract This paper presents an experimentally validated room-level computational fluid dynamics (CFD) model for raised-floor data center configurations employing active tiles. Active tiles are perforated floor tiles with integrated fans, which increase the local volume flow rate by redistributing the cold air supplied by the computer room air conditioning (CRAC) unit to the under-floor plenum. The numerical model of the data center room consists of one cold aisle with 12 racks arranged on both sides and three CRAC units sited around the periphery of the room. The commercial CFD software package futurefacilities6sigmadcx is used to develop the model for three configurations: (a) an aisle populated with ten (i.e., all) passive tiles; (b) a single active tile and nine passive tiles in the cold aisle; and (c) an aisle populated with all active tiles. The predictions from the CFD model are found to be in good agreement with the experimental data, with an average discrepancy between the measured and computed values for total flow rate and rack inlet temperature less than 4% and 1.7 °C, respectively. The validated models were then used to simulate steady-state and transient scenarios following cooling failure. This physics-based and experimentally validated room-level model can be used for temperature and flow distributions prediction and identifying optimal number and locations of active tiles for hot spot mitigation in data centers.

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