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Van den Eynde J, Westenberg JJM, Hazekamp MG, Lamb HJ, Jongbloed MRM, Wentzel JJ, Kenjeres S, Dekkers IA, Van De Bruaene A, Rijnberg FM, Roest AAW. Noninvasive Advanced Cardiovascular Magnetic Resonance-Derived Fontan Hemodynamics Are Associated With Reduced Kidney Function But Not Albuminuria. J Am Heart Assoc 2024; 13:e033122. [PMID: 38293946 PMCID: PMC11056124 DOI: 10.1161/jaha.123.033122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Accepted: 12/01/2023] [Indexed: 02/01/2024]
Abstract
BACKGROUND Kidney disease is the most important predictor of death in patients with a Fontan circulation, yet its clinical and hemodynamic correlates have not been well established. METHODS AND RESULTS A total of 53 ambulatory patients with a Fontan circulation (median age, 16.2 years, 52.8% male patients) underwent advanced cardiovascular magnetic resonance assessment, including 4-dimensional flow imaging and computational fluid dynamics. Estimated glomerular filtration rate (eGFR) <90 mL/min per 1.73 m2 was observed in 20.8% and albumin-to-creatinine ratio >3 mg/mmol in 39.6%. The average eGFR decline rate was -1.83 mL/min per 1.73 m2 per year (95% CI, -2.67 to -0.99; P<0.001). Lower eGFR was associated with older age, larger body surface area at examination, longer time since Fontan procedure, and lower systemic ventricular ejection fraction. Higher albumin-to-creatinine ratio was associated with absence of fenestration at the Fontan operation, and older age and lower systemic ventricular ejection fraction at the assessment. Lower cross-sectional area of the Fontan conduit indexed to flow (r=0.32, P=0.038), higher inferior vena cava-conduit velocity mismatch factor (r=-0.35, P=0.022), higher kinetic energy indexed to flow in the total cavopulmonary connection (r=-0.59, P=0.005), and higher total cavopulmonary connection resistance (r=-0.42, P=0.005 at rest; r=-0.43, P=0.004 during exercise) were all associated with lower eGFR but not with albuminuria. CONCLUSIONS Kidney dysfunction and albuminuria are common among clinically well adolescents and young adults with a Fontan circulation. Advanced cardiovascular magnetic resonance-derived metrics indicative of declining Fontan hemodynamics are associated with eGFR and might serve as targets to improve kidney health. Albuminuria might be driven by other factors that need further investigation.
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Affiliation(s)
- Jef Van den Eynde
- Department of Pediatrics, Division of Pediatric CardiologyLeiden University Medical CenterLeidenThe Netherlands
- Department of Cardiothoracic SurgeryLeiden University Medical CenterLeidenThe Netherlands
- Congenital and Structural CardiologyUniversity Hospitals LeuvenLeuvenBelgium
- Department of Cardiovascular SciencesCatholic University LeuvenLeuvenBelgium
| | - Jos J. M. Westenberg
- CardioVascular Imaging Group, Department of RadiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Mark G. Hazekamp
- Department of Cardiothoracic SurgeryLeiden University Medical CenterLeidenThe Netherlands
| | - Hildo J. Lamb
- CardioVascular Imaging Group, Department of RadiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Monique R. M. Jongbloed
- Department of CardiologyLeiden University Medical CenterLeidenThe Netherlands
- Department of Anatomy & EmbryologyLeiden University Medical CenterLeidenThe Netherlands
| | - Jolanda J. Wentzel
- Department of CardiologyBiomechanical Engineering, Erasmus MCRotterdamThe Netherlands
| | - Sasa Kenjeres
- Department of Chemical Engineering, Faculty of Applied SciencesDelft University of TechnologyDelftThe Netherlands
- J.M. Burgers Centrum Research School for Fluid MechanicsDelftThe Netherlands
| | - Ilona A. Dekkers
- CardioVascular Imaging Group, Department of RadiologyLeiden University Medical CenterLeidenThe Netherlands
| | - Alexander Van De Bruaene
- Congenital and Structural CardiologyUniversity Hospitals LeuvenLeuvenBelgium
- Department of Cardiovascular SciencesCatholic University LeuvenLeuvenBelgium
| | - Friso M. Rijnberg
- Department of Cardiothoracic SurgeryLeiden University Medical CenterLeidenThe Netherlands
| | - Arno A. W. Roest
- Department of Pediatrics, Division of Pediatric CardiologyLeiden University Medical CenterLeidenThe Netherlands
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Hut T, Roest A, Gaillard D, Hazekamp M, van den Boogaard P, Lamb H, Kroft L, Jongbloed M, Westenberg J, Wentzel J, Rijnberg F, Kenjeres S. Virtual surgery to predict optimized conduit size for adult Fontan patients with 16-mm conduits. Interdiscip Cardiovasc Thorac Surg 2023; 37:ivad126. [PMID: 37522877 PMCID: PMC10686953 DOI: 10.1093/icvts/ivad126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 06/18/2023] [Accepted: 07/30/2023] [Indexed: 08/01/2023]
Abstract
OBJECTIVES Recent evidence suggests that conduits implanted in Fontan patients at the age of 2-4 years become undersized for adulthood. The objective of this study is to use computational fluid dynamic models to evaluate the effect of virtual expansion of the Fontan conduit on haemodynamics and energetics of the total cavopulmonary connection (TCPC) under resting conditions and increased flow conditions. METHODS Patient-specific, magnetic resonance imaging-based simulation models of the TCPC were performed during resting and increased flow conditions. The original 16-mm conduits were virtually enlarged to 3 new sizes. The proposed conduit sizes were defined based on magnetic resonance imaging-derived conduit flow in each patient. Flow efficiency was evaluated based on power loss, pressure drop and resistance and thrombosis risk was based on flow stagnation volume and relative residence time (RRT). RESULTS Models of 5 adult patients with a 16-mm extracardiac Fontan connection were simulated and subsequently virtually expanded to 24-32 mm depending on patient-specific conduit flow. Virtual expansion led to a 40-65% decrease in pressure gradient across the TCPC depending on virtual conduit size. Despite improved energetics of the entire TCPC, the pulmonary arteries remained a significant contributor to energy loss (60-73% of total loss) even after virtual surgery. Flow stagnation volume inside the virtual conduit and surface area in case of elevated RRT (>20/Pa) increased after conduit enlargement but remained negligible (flow stagnation <2% of conduit volume in rest, <0.5% with exercise and elevated RRT <3% in rest, <1% with exercise). CONCLUSIONS Virtual expansion of 16-mm conduits to 24-32 mm, depending on patient-specific conduit flow, in Fontan patients significantly improves TCPC efficiency while thrombosis risk presumably remains low.
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Affiliation(s)
- Tjerry Hut
- Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology and J.M. Burgers Centrum Research School for Fluid Mechanics, Delft, Netherlands
| | - Arno Roest
- Department of Pediatric Cardiology, Leiden University Medical Center, Leiden, Netherlands
| | - Duco Gaillard
- Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology and J.M. Burgers Centrum Research School for Fluid Mechanics, Delft, Netherlands
| | - Mark Hazekamp
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, Netherlands
| | | | - Hildo Lamb
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Lucia Kroft
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Monique Jongbloed
- Department of Cardiology and Anatomy & Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Jos Westenberg
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Jolanda Wentzel
- Department of Cardiology, Biomechanical Engineering, Erasmus MC, Rotterdam, Netherlands
| | - Friso Rijnberg
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, Netherlands
| | - Sasa Kenjeres
- Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology and J.M. Burgers Centrum Research School for Fluid Mechanics, Delft, Netherlands
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Rijnberg FM, van ‘t Hul LC, Hazekamp MG, van den Boogaard PJ, Juffermans JF, Lamb HJ, Terol Espinosa de Los Monteros C, Kroft LJM, Kenjeres S, le Cessie S, Jongbloed MRM, Westenberg JJM, Roest AAW, Wentzel JJ. Haemodynamic performance of 16-20-mm extracardiac Goretex conduits in adolescent Fontan patients at rest and during simulated exercise. Eur J Cardiothorac Surg 2022; 63:6808623. [PMID: 36342204 PMCID: PMC9972516 DOI: 10.1093/ejcts/ezac522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 10/03/2022] [Accepted: 11/06/2022] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVES To date, it is not known if 16-20-mm extracardiac conduits are outgrown during somatic growth from childhood to adolescence. This study aims to determine total cavopulmonary connection (TCPC) haemodynamics in adolescent Fontan patients at rest and during simulated exercise and to assess the relationship between conduit size and haemodynamics. METHODS Patient-specific, magnetic resonance imaging-based computational fluid dynamic models of the TCPC were performed in 51 extracardiac Fontan patients with 16-20-mm conduits. Power loss, pressure gradient and normalized resistance were quantified in rest and during simulated exercise. The cross-sectional area (CSA) (mean and minimum) of the vessels of the TCPC was determined and normalized for flow rate (mm2/l/min). Peak (predicted) oxygen uptake was assessed. RESULTS The median age was 16.2 years (Q1-Q3 14.0-18.2). The normalized mean conduit CSA was 35-73% smaller compared to the inferior and superior vena cava, hepatic veins and left/right pulmonary artery (all P < 0.001). The median TCPC pressure gradient was 0.7 mmHg (Q1-Q3 0.5-0.8) and 2.0 (Q1-Q3 1.4-2.6) during rest and simulated exercise, respectively. A moderate-strong inverse non-linear relationship was present between normalized mean conduit CSA and TCPC haemodynamics in rest and exercise. TCPC pressure gradients of ≥1.0 at rest and ≥3.0 mmHg during simulated exercise were observed in patients with a conduit CSA ≤ 45 mm2/l/min and favourable haemodynamics (<1 mmHg during both rest and exercise) in conduits ≥125 mm2/l/min. Normalized TCPC resistance correlated with (predicted) peak oxygen uptake. CONCLUSIONS Extracardiac conduits of 16-20 mm have become relatively undersized in most adolescent Fontan patients leading to suboptimal haemodynamics.
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Affiliation(s)
- Friso M Rijnberg
- Corresponding author. Department of Cardiothoracic surgery, Leiden University Medical Center, Albinusdreef 2, 2333ZA, Leiden, the Netherlands, Telephone number:+31715262348 (F.M. Rijnberg)
| | - Luca C van ‘t Hul
- Department of Cardiology, Biomechanical Engineering, Erasmus MC, Rotterdam, Netherlands
| | - Mark G Hazekamp
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, Netherlands
| | | | - Joe F Juffermans
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Hildo J Lamb
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | | | - Lucia J M Kroft
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Sasa Kenjeres
- Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology and J.M. Burgers centrum Research School for Fluid Mechanics, Delft, Netherlands
| | - Saskia le Cessie
- Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, Netherlands
| | - Monique R M Jongbloed
- Department of Cardiology and Anatomy & Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Jos J M Westenberg
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
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Westenberg JJM, van Assen HC, van den Boogaard PJ, Goeman JJ, Saaid H, Voorneveld J, Bosch J, Kenjeres S, Claessens T, Garg P, Kouwenhoven M, Lamb HJ. Echo planar imaging-induced errors in intracardiac 4D flow MRI quantification. Magn Reson Med 2021; 87:2398-2411. [PMID: 34866236 PMCID: PMC9300143 DOI: 10.1002/mrm.29112] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 11/16/2021] [Accepted: 11/16/2021] [Indexed: 01/09/2023]
Abstract
Purpose To assess errors associated with EPI‐accelerated intracardiac 4D flow MRI (4DEPI) with EPI factor 5, compared with non‐EPI gradient echo (4DGRE). Methods Three 3T MRI experiments were performed comparing 4DEPI to 4DGRE: steady flow through straight tubes, pulsatile flow in a left‐ventricle phantom, and intracardiac flow in 10 healthy volunteers. For each experiment, 4DEPI was repeated with readout and blip phase‐encoding gradient in different orientations, parallel or perpendicular to the flow direction. In vitro flow rates were compared with timed volumetric collection. In the left‐ventricle phantom and in vivo, voxel‐based speed and spatio‐temporal median speed were compared between sequences, as well as mitral and aortic transvalvular net forward volume. Results In steady‐flow phantoms, the flow rate error was largest (12%) for high velocity (>2 m/s) with 4DEPI readout gradient parallel to the flow. Voxel‐based speed and median speed in the left‐ventricle phantom were ≤5.5% different between sequences. In vivo, mean net forward volume inconsistency was largest (6.4 ± 8.5%) for 4DEPI with nonblip phase‐encoding gradient parallel to the main flow. The difference in median speed for 4DEPI versus 4DGRE was largest (9%) when the 4DEPI readout gradient was parallel to the flow. Conclusions Velocity and flow rate are inaccurate for 4DEPI with EPI factor 5 when flow is parallel to the readout or blip phase‐encoding gradient. However, mean differences in flow rate, voxel‐based speed, and spatio‐temporal median speed were acceptable (≤10%) when comparing 4DEPI to 4DGRE for intracardiac flow in healthy volunteers.
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Affiliation(s)
- Jos J M Westenberg
- CardioVascular Imaging Group, Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Hans C van Assen
- CardioVascular Imaging Group, Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Pieter J van den Boogaard
- CardioVascular Imaging Group, Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | - Jelle J Goeman
- Department of Biomedical Data Sciences, Leiden University Medical Center, Leiden, the Netherlands
| | - Hicham Saaid
- Institute Biomedical Technology, Ghent University, Ghent, Belgium
| | - Jason Voorneveld
- Department of Biomedical Engineering, Erasmus Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Johan Bosch
- Department of Biomedical Engineering, Erasmus Medical Center Rotterdam, Rotterdam, the Netherlands
| | - Sasa Kenjeres
- Department of Chemical Engineering, Delft University of Technology, Delft, the Netherlands
| | - Tom Claessens
- Department of Materials, Textiles and Chemical Engineering, Ghent University, Ghent, Belgium
| | - Pankaj Garg
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, UK
| | - Marc Kouwenhoven
- Department of MR R&D-Clinical Science, Philips, Best, the Netherlands
| | - Hildo J Lamb
- CardioVascular Imaging Group, Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
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Rijnberg FM, van der Woude SFS, Hazekamp MG, van den Boogaard PJ, Lamb HJ, Terol Espinosa de Los Monteros C, Kroft LJM, Kenjeres S, Karim T, Jongbloed MRM, Westenberg JJM, Wentzel JJ, Roest AAW. Extracardiac conduit adequacy along the respiratory cycle in adolescent Fontan patients. Eur J Cardiothorac Surg 2021; 62:6423130. [PMID: 34747442 PMCID: PMC9257669 DOI: 10.1093/ejcts/ezab478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 09/12/2021] [Accepted: 09/26/2021] [Indexed: 11/30/2022] Open
Affiliation(s)
- Friso M Rijnberg
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, Netherlands
| | | | - Mark G Hazekamp
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, Netherlands
| | | | - Hildo J Lamb
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | | | - Lucia J M Kroft
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Sasa Kenjeres
- Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology and J.M. Burgers Centrum Research School for Fluid Mechanics, Delft, Netherlands
| | - Tawab Karim
- Department of Cardiology, Biomechanical Engineering, Erasmus MC, Rotterdam, Netherlands
| | - Monique R M Jongbloed
- Department of Cardiology and Anatomy and Embryology, Leiden University Medical Center, Leiden, Netherlands
| | - Jos J M Westenberg
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Jolanda J Wentzel
- Department of Cardiology, Biomechanical Engineering, Erasmus MC, Rotterdam, Netherlands
| | - Arno A W Roest
- Department of Pediatric Cardiology, Leiden University Medical Center, Leiden, Netherlands
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van der Woude SFS, Rijnberg FM, Hazekamp MG, Jongbloed MRM, Kenjeres S, Lamb HJ, Westenberg JJM, Roest AAW, Wentzel JJ. The Influence of Respiration on Blood Flow in the Fontan Circulation: Insights for Imaging-Based Clinical Evaluation of the Total Cavopulmonary Connection. Front Cardiovasc Med 2021; 8:683849. [PMID: 34422920 PMCID: PMC8374887 DOI: 10.3389/fcvm.2021.683849] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 07/05/2021] [Indexed: 12/18/2022] Open
Abstract
Congenital heart disease is the most common birth defect and functionally univentricular heart defects represent the most severe end of this spectrum. The Fontan circulation provides an unique solution for single ventricle patients, by connecting both caval veins directly to the pulmonary arteries. As a result, the pulmonary circulation in Fontan palliated patients is characterized by a passive, low-energy circulation that depends on increased systemic venous pressure to drive blood toward the lungs. The absence of a subpulmonary ventricle led to the widely believed concept that respiration, by sucking blood to the pulmonary circulation during inspiration, is of great importance as a driving force for antegrade blood flow in Fontan patients. However, recent studies show that respiration influences pulsatility, but has a limited effect on net forward flow in the Fontan circulation. Importantly, since MRI examination is recommended every 2 years in Fontan patients, clinicians should be aware that most conventional MRI flow sequences do not capture the pulsatility of the blood flow as a result of the respiration. In this review, the unique flow dynamics influenced by the cardiac and respiratory cycle at multiple locations within the Fontan circulation is discussed. The impact of (not) incorporating respiration in different MRI flow sequences on the interpretation of clinical flow parameters will be covered. Finally, the influence of incorporating respiration in advanced computational fluid dynamic modeling will be outlined.
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Affiliation(s)
- Séline F S van der Woude
- Department of Cardiology, Biomedical Engineering, Biomechanics Laboratory, Rotterdam, Netherlands
| | - Friso M Rijnberg
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, Netherlands
| | - Mark G Hazekamp
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, Netherlands
| | - Monique R M Jongbloed
- Department of Anatomy, Embryology and Cardiology, Leiden University Medical Center, Leiden, Netherlands
| | - Sasa Kenjeres
- Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology and J. M. Burgerscentrum Research School for Fluid Mechanics, Delft, Netherlands
| | - Hildo J Lamb
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Jos J M Westenberg
- Department of Radiology, Leiden University Medical Center, Leiden, Netherlands
| | - Arno A W Roest
- Department of Pediatric Cardiology, Leiden University Medical Center, Leiden, Netherlands
| | - Jolanda J Wentzel
- Department of Cardiology, Biomedical Engineering, Biomechanics Laboratory, Rotterdam, Netherlands
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Ramaekers MJFG, Adriaans BP, Juffermans JF, van Assen HC, Bekkers SCAM, Scholte AJHA, Kenjeres S, Lamb HJ, Wildberger JE, Westenberg JJM, Schalla S. Characterization of Ascending Aortic Flow in Patients With Degenerative Aneurysms: A 4D Flow Magnetic Resonance Study. Invest Radiol 2021; 56:494-500. [PMID: 33653992 DOI: 10.1097/rli.0000000000000768] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES Degenerative thoracic aortic aneurysm (TAA) patients are known to be at risk of life-threatening acute aortic events. Guidelines recommend preemptive surgery at diameters of greater than 55 mm, although many patients with small aneurysms show only mild growth rates and more than half of complications occur in aneurysms below this threshold. Thus, assessment of hemodynamics using 4-dimensional flow magnetic resonance has been of interest to obtain more insights in aneurysm development. Nonetheless, the role of aberrant flow patterns in TAA patients is not yet fully understood. MATERIALS AND METHODS A total of 25 TAA patients and 22 controls underwent time-resolved 3-dimensional phase contrast magnetic resonance imaging with 3-directional velocity encoding (ie, 4-dimensional flow magnetic resonance imaging). Hemodynamic parameters such as vorticity, helicity, and wall shear stress (WSS) were calculated from velocity data in 3 anatomical segments of the ascending aorta (root, proximal, and distal). Regional WSS distribution was assessed for the full cardiac cycle. RESULTS Flow vorticity and helicity were significantly lower for TAA patients in all segments. The proximal ascending aorta showed a significant increase in peak WSS in the outer curvature in TAA patients, whereas WSS values at the inner curvature were significantly lower as compared with controls. Furthermore, positive WSS gradients from sinotubular junction to midascending aorta were most prominent in the outer curvature, whereas from midascending aorta to brachiocephalic trunk, the outer curvature showed negative WSS gradients in the TAA group. Controls solely showed a positive gradient at the inner curvature for both segments. CONCLUSIONS Degenerative TAA patients show a decrease in flow vorticity and helicity, which is likely to cause perturbations in physiological flow patterns. The subsequent differing distribution of WSS might be a contributor to vessel wall remodeling and aneurysm formation.
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Affiliation(s)
| | | | | | | | | | | | - Sasa Kenjeres
- Department of Chemical Engineering, Transport Phenomena Section, Faculty of Applied Sciences, Delft University of Technology, Delft, the Netherlands
| | - Hildo J Lamb
- Department of Radiology, Leiden University Medical Center
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Rijnberg FM, van der Woude SFS, van Assen HC, Juffermans JF, Hazekamp MG, Jongbloed MRM, Kenjeres S, Lamb HJ, Westenberg JJM, Wentzel JJ, Roest AAW. Non-uniform mixing of hepatic venous flow and inferior vena cava flow in the Fontan conduit. J R Soc Interface 2021; 18:20201027. [PMID: 33823607 PMCID: PMC8086942 DOI: 10.1098/rsif.2020.1027] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Fontan patients require a balanced hepatic blood flow distribution (HFD) to prevent pulmonary arteriovenous malformations. Currently, HFD is quantified by tracking Fontan conduit flow, assuming hepatic venous (HV) flow to be uniformly distributed within the Fontan conduit. However, this assumption may be unvalid leading to inaccuracies in HFD quantification with potential clinical impact. The aim of this study was to (i) assess the mixing of HV flow and inferior vena caval (IVC) flow within the Fontan conduit and (ii) quantify HFD by directly tracking HV flow and quantitatively comparing results with the conventional approach. Patient-specific, time-resolved computational fluid dynamic models of 15 total cavopulmonary connections were generated, including the HV and subhepatic IVC. Mixing of HV and IVC flow, on a scale between 0 (no mixing) and 1 (perfect mixing), was assessed at the caudal and cranial Fontan conduit. HFD was quantified by tracking particles from the caudal (HFDcaudal conduit) and cranial (HFDcranial conduit) conduit and from the hepatic veins (HFDHV). HV flow was non-uniformly distributed at both the caudal (mean mixing 0.66 ± 0.13) and cranial (mean 0.79 ± 0.11) level within the Fontan conduit. On a cohort level, differences in HFD between methods were significant but small; HFDHV (51.0 ± 20.6%) versus HFDcaudal conduit (48.2 ± 21.9%, p = 0.033) or HFDcranial conduit (48.0 ± 21.9%, p = 0.044). However, individual absolute differences of 8.2–14.9% in HFD were observed in 4/15 patients. HV flow is non-uniformly distributed within the Fontan conduit. Substantial individual inaccuracies in HFD quantification were observed in a subset of patients with potential clinical impact.
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Affiliation(s)
- Friso M Rijnberg
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Hans C van Assen
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Joe F Juffermans
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Mark G Hazekamp
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, The Netherlands
| | - Monique R M Jongbloed
- Department of Cardiology and Anatomy and Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | - Sasa Kenjeres
- Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology and J. M. Burgerscentrum Research School for Fluid Mechanics, Delft, The Netherlands
| | - Hildo J Lamb
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jos J M Westenberg
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jolanda J Wentzel
- Department of Cardiology, Biomedical Engineering, Erasmus MC, Rotterdam, The Netherlands
| | - Arno A W Roest
- Department of Pediatric Cardiology, Leiden University Medical Center, Leiden, The Netherlands
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Kenjeres S, Henry FS, Tsuda A. Is Current Social Distancing Enough? Ann Biomed Eng 2021; 49:1973-1974. [PMID: 33575929 PMCID: PMC7878170 DOI: 10.1007/s10439-021-02741-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Indexed: 11/19/2022]
Affiliation(s)
- Sasa Kenjeres
- Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, 2629 HZ, Delft, The Netherlands.
| | - Frank S Henry
- Department of Mechanical Engineering, Manhattan College, Riverdale, NY, 10471, USA
| | - Akira Tsuda
- Tsuda Lung Research, Shrewsbury, MA, 01545, USA.
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Voorneveld J, Saaid H, Schinkel C, Radeljic N, Lippe B, Gijsen FJH, van der Steen AFW, de Jong N, Claessens T, Vos HJ, Kenjeres S, Bosch JG. 4-D Echo-Particle Image Velocimetry in a Left Ventricular Phantom. Ultrasound Med Biol 2020; 46:805-817. [PMID: 31924419 DOI: 10.1016/j.ultrasmedbio.2019.11.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 10/29/2019] [Accepted: 11/30/2019] [Indexed: 06/10/2023]
Abstract
Left ventricular (LV) blood flow is an inherently complex time-varying 3-D phenomenon, where 2-D quantification often ignores the effect of out-of-plane motion. In this study, we describe high frame rate 4-D echocardiographic particle image velocimetry (echo-PIV) using a prototype matrix transesophageal transducer and a dynamic LV phantom for testing the accuracy of echo-PIV in the presence of complex flow patterns. Optical time-resolved tomographic PIV (tomo-PIV) was used as a reference standard for comparison. Echo-PIV and tomo-PIV agreed on the general profile of the LV flow patterns, but echo-PIV smoothed out the smaller flow structures. Echo-PIV also underestimated the flow rates at greater imaging depths, where the PIV kernel size and transducer point spread function were large relative to the velocity gradients. We demonstrate that 4-D echo-PIV could be performed in just four heart cycles, which would require only a short breath-hold, providing promising results. However, methods for resolving high velocity gradients in regions of poor spatial resolution are required before clinical translation.
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Affiliation(s)
- Jason Voorneveld
- Department of Biomedical Engineering, Thorax Center, Erasmus MC University Medical Center, Rotterdam, the Netherlands.
| | - Hicham Saaid
- Institute Biomedical Technology, Ghent University, Ghent, Belgium
| | - Christiaan Schinkel
- Transport Phenomena Section, Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology; the Netherlands
| | | | | | - Frank J H Gijsen
- Department of Biomedical Engineering, Thorax Center, Erasmus MC University Medical Center, Rotterdam, the Netherlands
| | - Antonius F W van der Steen
- Department of Biomedical Engineering, Thorax Center, Erasmus MC University Medical Center, Rotterdam, the Netherlands; Laboratory of Acoustical Wavefield Imaging, Faculty of Applied Sciences, Delft University of Technology, Delft, the Netherlands
| | - Nico de Jong
- Department of Biomedical Engineering, Thorax Center, Erasmus MC University Medical Center, Rotterdam, the Netherlands; Laboratory of Acoustical Wavefield Imaging, Faculty of Applied Sciences, Delft University of Technology, Delft, the Netherlands
| | - Tom Claessens
- Department of Materials, Textiles and Chemical Engineering, Ghent University, Ghent, Belgium
| | - Hendrik J Vos
- Department of Biomedical Engineering, Thorax Center, Erasmus MC University Medical Center, Rotterdam, the Netherlands; Laboratory of Acoustical Wavefield Imaging, Faculty of Applied Sciences, Delft University of Technology, Delft, the Netherlands
| | - Sasa Kenjeres
- Transport Phenomena Section, Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology; the Netherlands
| | - Johan G Bosch
- Department of Biomedical Engineering, Thorax Center, Erasmus MC University Medical Center, Rotterdam, the Netherlands
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11
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van As K, Boterman J, Kleijn CR, Kenjeres S, Bhattacharya N. Laser speckle imaging of flowing blood: A numerical study. Phys Rev E 2020; 100:033317. [PMID: 31639980 DOI: 10.1103/physreve.100.033317] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Indexed: 11/07/2022]
Abstract
Laser speckle imaging (LSI) can be used to study dynamic processes in turbid media, such as blood flow. However, it is presently still challenging to obtain meaningful quantitative information from speckle, mainly because speckle is the interferometric summation of multiply scattered light. Consequently, speckle represents a convolution of the local dynamics of the medium. In this paper, we present a computational model for simulating the LSI process, which we aim to use for improving our understanding of the underlying physics. Thereby reliable methods for extracting meaningful information from speckle can be developed. To validate our code, we apply it to a case study resembling blood flow: a cylindrical fluid flow geometry seeded with small spherical particles and modulated with a heartbeat signal. From the simulated speckle pattern, we successfully retrieve the main frequency modes of the original heartbeat signal. By comparing Poiseuille flow to plug flow, we show that speckle boiling causes a small amount of uniform spectral noise. Our results indicate that our computational model is capable of simulating LSI and will therefore be useful in future studies for further developing LSI as a quantitative imaging tool.
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Affiliation(s)
- Kevin van As
- Delft University of Technology, Faculty of Applied Sciences, Dept. of Chemical Engineering, 2629 HZ Delft, The Netherlands.,JM Burgerscentrum for Fluid Mechanics, 2628 CD Delft, The Netherlands
| | - Jorne Boterman
- Delft University of Technology, Faculty of Applied Sciences, Dept. of Chemical Engineering, 2629 HZ Delft, The Netherlands
| | - Chris R Kleijn
- Delft University of Technology, Faculty of Applied Sciences, Dept. of Chemical Engineering, 2629 HZ Delft, The Netherlands.,JM Burgerscentrum for Fluid Mechanics, 2628 CD Delft, The Netherlands
| | - Sasa Kenjeres
- Delft University of Technology, Faculty of Applied Sciences, Dept. of Chemical Engineering, 2629 HZ Delft, The Netherlands.,JM Burgerscentrum for Fluid Mechanics, 2628 CD Delft, The Netherlands
| | - Nandini Bhattacharya
- Delft University of Technology, Faculty of Applied Sciences, Dept. of Imaging Physics, 2628 CJ Delft, The Netherlands
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12
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Saaid H, Voorneveld J, Schinkel C, Westenberg J, Gijsen F, Segers P, Verdonck P, de Jong N, Bosch JG, Kenjeres S, Claessens T. Tomographic PIV in a model of the left ventricle: 3D flow past biological and mechanical heart valves. J Biomech 2019; 90:40-49. [DOI: 10.1016/j.jbiomech.2019.04.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 03/14/2019] [Accepted: 04/15/2019] [Indexed: 10/27/2022]
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13
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Khalafvand SS, Xu F, Westenberg J, Gijsen F, Kenjeres S. Intraventricular blood flow with a fully dynamic mitral valve model. Comput Biol Med 2019; 104:197-204. [DOI: 10.1016/j.compbiomed.2018.11.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 11/27/2018] [Accepted: 11/28/2018] [Indexed: 11/25/2022]
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14
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Voorneveld J, Muralidharan A, Hope T, Vos HJ, Kruizinga P, van der Steen AFW, Gijsen FJH, Kenjeres S, de Jong N, Bosch JG. High Frame Rate Ultrasound Particle Image Velocimetry for Estimating High Velocity Flow Patterns in the Left Ventricle. IEEE Trans Ultrason Ferroelectr Freq Control 2018; 65:2222-2232. [PMID: 29990263 DOI: 10.1109/tuffc.2017.2786340] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Echocardiographic determination of multicomponent blood flow dynamics in the left ventricle remains a challenge. In this paper, we compare contrast enhanced, high frame rate (HFR) (1000 frames/s) echo-particle image velocimetry (ePIV) against optical particle image velocimetry (oPIV, gold standard), in a realistic left ventricular (LV) phantom. We find that ePIV compares well to oPIV, even for the high velocity inflow jet (normalized RMSE = 9% ± 1%). In addition, we perform the method of proper orthogonal decomposition, to better qualify and quantify the differences between the two modalities. We show that ePIV and oPIV resolve very similar flow structures, especially for the lowest order mode with a cosine similarity index of 86%. The coarser resolution of ePIV does result in increased variance and blurring of smaller flow structures when compared to oPIV. However, both modalities are in good agreement with each other for the modes that constitute the bulk of the kinetic energy. We conclude that HFR ePIV can accurately estimate the high velocity diastolic inflow jet and the high energy flow structures in an LV setting.
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15
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Nemati M, Loozen GB, van der Wekken N, van de Belt G, Urbach HP, Bhattacharya N, Kenjeres S. Application of full field optical studies for pulsatile flow in a carotid artery phantom. Biomed Opt Express 2015; 6:4037-50. [PMID: 26504652 PMCID: PMC4605061 DOI: 10.1364/boe.6.004037] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 07/21/2015] [Accepted: 08/12/2015] [Indexed: 05/04/2023]
Abstract
A preliminary comparative measurement between particle imaging velocimetry (PIV) and laser speckle contrast analysis (LASCA) to study pulsatile flow using ventricular assist device in a patient-specific carotid artery phantom is reported. These full-field optical techniques have both been used to study flow and extract complementary parameters. We use the high spatial resolution of PIV to generate a full velocity map of the flow field and the high temporal resolution of LASCA to extract the detailed frequency spectrum of the fluid pulses. Using this combination of techniques a complete study of complex pulsatile flow in an intricate flow network can be studied.
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Affiliation(s)
- M. Nemati
- Department of Imaging Physics, Delft University of Technology, Delft, The
Netherlands
| | - G. B. Loozen
- Department of Imaging Physics, Delft University of Technology, Delft, The
Netherlands
| | - N. van der Wekken
- Transport Phenomena Section, Department of Chemical Engineering, Faculty of Applied Sciences and J. M. Burgerscentrum for Fluid Mechanics, Delft University of Technology, Delft, The
Netherlands
| | - G. van de Belt
- Transport Phenomena Section, Department of Chemical Engineering, Faculty of Applied Sciences and J. M. Burgerscentrum for Fluid Mechanics, Delft University of Technology, Delft, The
Netherlands
| | - H. P. Urbach
- Department of Imaging Physics, Delft University of Technology, Delft, The
Netherlands
| | - N. Bhattacharya
- Department of Imaging Physics, Delft University of Technology, Delft, The
Netherlands
| | - S. Kenjeres
- Transport Phenomena Section, Department of Chemical Engineering, Faculty of Applied Sciences and J. M. Burgerscentrum for Fluid Mechanics, Delft University of Technology, Delft, The
Netherlands
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16
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Haverkort JW, Kenjeres S, Kleijn CR. Magnetic particle motion in a Poiseuille flow. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 80:016302. [PMID: 19658801 DOI: 10.1103/physreve.80.016302] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2009] [Revised: 05/25/2009] [Indexed: 05/28/2023]
Abstract
The manipulation of magnetic particles in a continuous flow with magnetic fields is central to several biomedical applications, including magnetic cell separation and magnetic drug targeting. A simplified two-dimensional (2D) equation describing the motion of particles in a planar Poiseuille flow is considered for various magnetic field configurations. Exact analytical solutions are derived for the particle motion under the influence of a constant magnetization force and a force decaying as a power of the source distance, e.g., due to a current carrying wire or a magnetized cylinder. For a source distance much larger than the transversal size of the flow, a general solution is derived and applied to the important case of a magnetic dipole. This solution is used to investigate the dependence of the particle capture efficiency on the dipole orientation. A correction factor to convert the obtained 2D results to a three-dimensional cylindrical geometry is derived and validated against computational simulations. Simulations are also used to investigate parameter ranges beyond the region of applicability of the analytical results and to investigate more complex magnetic field configurations.
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Affiliation(s)
- J W Haverkort
- Department of Multi-Scale Physics, Delft University of Technology, Prins Bernhardlaan 6, 2628 BW Delft, The Netherlands.
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17
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Abstract
We performed large eddy simulations (LES) of the turbulent natural convection of an electrically conductive fluid (water with 7% Na2SO4 electrolyte solution) in a moderate (4:4:1) aspect ratio enclosure heated from below and cooled from above and subjected to external nonuniformly distributed electromagnetic fields. Different configurations with permanent magnets (located under the lower thermally active wall, B_{0}=1T ) and different strengths of imposed dc electric currents ( I=0-10A ) were compared to the case of pure thermal convection in the turbulent regime, Ra=10;{7} , Pr=7 . It is demonstrated that the electromagnetic forcing of the boundary layers caused significant reorganization of flow and turbulence structures producing significant enhancement of the wall-heat transfer (up to 188% for a configuration with 35 magnets and an applied dc current of 10A ).
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Affiliation(s)
- Sasa Kenjeres
- Department of Multi-Scale Physics and J.M. Burgers Centre for Fluid Dynamics, Delft University of Technology, Prins Bernhardlaan 6, 2628 BW Delft, The Netherlands
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Abstract
We present numerical simulations of a turbulent magnetic dynamo mimicking closely the Riga-dynamo experiment at Re approximately 3.5x10(6) and 15< or =Rem< or =20. The Reynolds-averaged Navier-Stokes equations for the fluid flow and turbulence field are solved simultaneously with the direct numerical solution of the magnetic field equations. The fully integrated two-way-coupled simulations reproduced all features of the magnetic self-excitation detected by the Riga experiment, with frequencies and amplitudes of the self-generated magnetic field in good agreement with the experimental records, and provided full insight into the unsteady magnetic and velocity fields and the mechanisms of the dynamo action.
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Affiliation(s)
- S Kenjeres
- Department of Multi Scale Physics, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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20
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Kenjeres S, Hanjalic K. Large eddy simulations of turbulent thermal convection at high Rayleigh number. J Vis (Tokyo) 2004. [DOI: 10.1007/bf03181577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Abstract
Large-scale vortical structures, found in many flows in nature, in laboratory or industrial equipment, have often a deterministic character. Simulation, identification, visualization, and interpretation of such structures is essential for understanding the physics of turbulence and transport processes, and for their control, but still poses a challenge especially in complex flows at high Reynolds and Rayleigh numbers. We show that such structures can be simulated by a transient Reynolds-averaged Navier-Stokes (T-RANS) approach. Various structure-identification methods show that the captured deterministic structures resemble closely those obtained from experiments or direct numerical simulations (DNS). The potential of the T-RANS method is illustrated by examples of classical and magnetic Rayleigh-Bénard (R-B) convection in a range of Rayleigh numbers that are at present inaccessible to experiments or other simulation techniques.
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Affiliation(s)
- Kemal Hanjalić
- Department of Applied Physics, Delft University of Technology, the Netherlands.
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22
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Kenjeres S, Hanjalić K. Numerical insight into flow structure in ultraturbulent thermal convection. Phys Rev E Stat Nonlin Soft Matter Phys 2002; 66:036307. [PMID: 12366253 DOI: 10.1103/physreve.66.036307] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2001] [Indexed: 05/23/2023]
Abstract
Very large eddy simulations of high-aspect-ratio unbounded Rayleigh-Bénard convection for Pr=0.71 over a 10-decade range of Rayleigh numbers (Ra=10(5)-10(15)) reveal a consolidation and dramatic thinning of the wall boundary layer with an increase in the Ra number. The fingerlike plumes between planform structures become also thinner, more distant, but much more vigorous. The Ra exponent in the Nu proportional to Ra(n) correlation follows n approximately 0.31 scaling, but n begins to increase gradually above Ra=10(13). However, no trend towards "crossing" of the thermal and hydrodynamic boundary layers is observed.
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Affiliation(s)
- S Kenjeres
- Department of Applied Physics, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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Kenjeres S, Hanjalic K. Convective rolls and heat transfer in finite-length rayleigh-Benard convection: A two-dimensional numerical study. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 2000; 62:7987-98. [PMID: 11138083 DOI: 10.1103/physreve.62.7987] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2000] [Indexed: 11/07/2022]
Abstract
A two-dimensional (2D) numerical study using a single-point algebraic k-straight theta;(2)-varepsilon-varepsilon(straight theta) turbulence closure was performed to detect the existence, origin, creation and behavior of convective rolls and associated wall Nusselt (Nu) number variation in thermal convection in 2D horizontal slender enclosures heated from below. The study covered the Rayleigh (Ra) numbers from 10(5) to 10(12) and aspect ratios from 4:1 to 32:1. The time evolution of the convective rolls and the formation of the corner vortices were analyzed using numerical flow visualization, and the correlation between roll structures and heat transfer established. A major consequence of the imposed two dimensionality appeared in the persistence of regular roll structures at higher Ra numbers that approach a steady state for all configurations considered. This finding contradicts the full three-dimensional direct numerical simulations (DNS), large eddy simulations (LES), and three-dimensional transient Reynolds-averaged Navier-Stokes (TRANS) computations, which all show continuously changing unsteady patterns. However, the final-stage roll structures, long-term averaged mean temperature and turbulence moments, and the Nusselt number (both local and integral), are all reproduced in good agreement with the ensemble-averaged 3D DNS, TRANS, and several recent experimental results. These findings justified the 2D approach as an acceptable method for ensemble average analysis of fully 3D flows with at least one homogeneous direction. Based on our 2D computations and adopting the low and high Ra number asymptotic power laws of Grossmann and Lohse [J. Fluid Mech. 407, 27 (2000)], new prefactors in the Nu-Ra correlation for Pr=O(1) were proposed that fit better several sets of data over a wide range of Ra numbers and aspect ratios: Nu=0.1Ra(1/4)+0.05Ra(1/3). Even better agreement of our computations was achieved with the new correlation Nu=0.124 Ra0.309 proposed recently by Niemela et al. [Nature (London) 404, 837 (2000)] for 10(6)</=Ra</=10(17).
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Affiliation(s)
- S Kenjeres
- Department of Applied Physics, Thermo-Fluids Section, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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