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Taglienti D, Guglietta F, Sbragaglia M. Droplet dynamics in homogeneous isotropic turbulence with the immersed boundary-lattice Boltzmann method. Phys Rev E 2024; 110:015302. [PMID: 39160985 DOI: 10.1103/physreve.110.015302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 06/05/2024] [Indexed: 08/21/2024]
Abstract
We develop a numerical method for simulating the dynamics of a droplet immersed in a generic time-dependent velocity gradient field. This approach is grounded on the hybrid coupling between the lattice Boltzmann (LB) method, employed for the flow simulation, and the immersed boundary (IB) method, utilized to couple the droplet with the surrounding fluid. We show how to enrich the numerical scheme with a mesh regularization technique, allowing droplets to sustain large deformations. The resulting methodology is adapted to simulate the dynamics of droplets in homogeneous and isotropic turbulence, with the characteristic size of the droplet being smaller than the characteristic Kolmogorov scale of the outer turbulent flow. We report statistical results for droplet deformation and orientation collected from an ensemble of turbulent trajectories, as well as comparisons with theoretical models in the limit of small deformation.
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Konnigk L, Torner B, Bruschewski M, Grundmann S, Wurm FH. Equivalent Scalar Stress Formulation Taking into Account Non-Resolved Turbulent Scales. Cardiovasc Eng Technol 2021; 12:251-272. [PMID: 33675019 PMCID: PMC8169507 DOI: 10.1007/s13239-021-00526-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 02/09/2021] [Indexed: 01/01/2023]
Abstract
PURPOSE Cardiovascular engineering includes flows with fluid-dynamical stresses as a parameter of interest. Mechanical stresses are high-risk factors for blood damage and can be assessed by computational fluid dynamics. By now, it is not described how to calculate an adequate scalar stress out of turbulent flow regimes when the whole share of turbulence is not resolved by the simulation method and how this impacts the stress calculation. METHODS We conducted direct numerical simulations (DNS) of test cases (a turbulent channel flow and the FDA nozzle) in order to access all scales of flow movement. After validation of both DNS with literature und experimental data using magnetic resonance imaging, the mechanical stress is calculated as a baseline. Afterwards, same flows are calculated using state-of-the-art turbulence models. The stresses are computed for every result using our definition of an equivalent scalar stress, which includes the influence from respective turbulence model, by using the parameter dissipation. Afterwards, the results are compared with the baseline data. RESULTS The results show a good agreement regarding the computed stress. Even when no turbulence is resolved by the simulation method, the results agree well with DNS data. When the influence of non-resolved motion is neglected in the stress calculation, it is underpredicted in all cases. CONCLUSION With the used scalar stress formulation, it is possible to include information about the turbulence of the flow into the mechanical stress calculation even when the used simulation method does not resolve any turbulence.
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Affiliation(s)
- Lucas Konnigk
- Institute of Turbomachinery, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, Rostock, Germany.
| | - Benjamin Torner
- Institute of Turbomachinery, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, Rostock, Germany
| | - Martin Bruschewski
- Institute of Fluid Mechanics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, Rostock, Germany
| | - Sven Grundmann
- Institute of Fluid Mechanics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, Rostock, Germany
| | - Frank-Hendrik Wurm
- Institute of Turbomachinery, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, Rostock, Germany
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Torner B, Konnigk L, Abroug N, Wurm H. Turbulence and turbulent flow structures in a ventricular assist device-A numerical study using the large-eddy simulation. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2021; 37:e3431. [PMID: 33336869 DOI: 10.1002/cnm.3431] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 12/14/2020] [Accepted: 12/14/2020] [Indexed: 06/12/2023]
Abstract
Numerical flow simulations that analyze the turbulent flow characteristics within a turbopump are important for optimizing the efficiency of such machines. In the case of ventricular assist devices (VADs), turbulent flow characteristics must be also examined in order to improve hemocompatibility. Turbulence increases the shear stresses in the VAD flow, which can lead to an increased damage to the transported blood components. Therefore, an understanding of the turbulent flow patterns and their significance for the numerical blood damage prediction is particularly important for flow optimizations in VADs in order to identify and thus minimize flow regions where blood could be damaged due to high turbulent stresses. Nevertheless, the turbulence occurring in VADs and the local turbulent structures that lead to increased turbulent stresses have not yet been analyzed in detail in these machines. Therefore, this study aims to investigate the turbulence in an axial VAD in a comprehensive and double tracked way. First, the flow in an axial VAD was computed using the large-eddy simulation method, and it was verified that the majority of the turbulence was directly resolved by the simulation. Then, the turbulent flow state of the VAD was quantified globally. For this purpose, a self-designed evaluation method, the power loss analysis, was used. Subsequently, local flow regions and flow structures were identified where significant turbulent stresses prevail. It will be shown that the identified regions are universal and will also occur in other axial blood pumps as well, for example, in the HeartMate II.
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Affiliation(s)
- Benjamin Torner
- Faculty of Mechanical Engineering and Marine Technology, Institute of Turbomachinery, University of Rostock, Rostock, Germany
| | - Lucas Konnigk
- Faculty of Mechanical Engineering and Marine Technology, Institute of Turbomachinery, University of Rostock, Rostock, Germany
| | - Nada Abroug
- Faculty of Mechanical Engineering and Marine Technology, Institute of Turbomachinery, University of Rostock, Rostock, Germany
| | - Hendrik Wurm
- Faculty of Mechanical Engineering and Marine Technology, Institute of Turbomachinery, University of Rostock, Rostock, Germany
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Assessment of the Flow Field in the HeartMate 3 Using Three-Dimensional Particle Tracking Velocimetry and Comparison to Computational Fluid Dynamics. ASAIO J 2020; 66:173-182. [DOI: 10.1097/mat.0000000000000987] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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Hong JK, Gao L, Singh J, Goh T, Ruhoff AM, Neto C, Waterhouse A. Evaluating medical device and material thrombosis under flow: current and emerging technologies. Biomater Sci 2020; 8:5824-5845. [DOI: 10.1039/d0bm01284j] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This review highlights the importance of flow in medical device thrombosis and explores current and emerging technologies to evaluate dynamic biomaterial Thrombosis in vitro.
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Affiliation(s)
- Jun Ki Hong
- School of Chemistry
- The University of Sydney
- Australia
- School of Medical Sciences
- Faculty of Medicine and Health
| | - Lingzi Gao
- Heart Research Institute
- Newtown
- Australia
- The University of Sydney Nano Institute
- The University of Sydney
| | - Jasneil Singh
- Heart Research Institute
- Newtown
- Australia
- The Charles Perkins Centre
- The University of Sydney
| | - Tiffany Goh
- Heart Research Institute
- Newtown
- Australia
- The Charles Perkins Centre
- The University of Sydney
| | - Alexander M. Ruhoff
- Heart Research Institute
- Newtown
- Australia
- The Charles Perkins Centre
- The University of Sydney
| | - Chiara Neto
- School of Chemistry
- The University of Sydney
- Australia
- The University of Sydney Nano Institute
- The University of Sydney
| | - Anna Waterhouse
- School of Medical Sciences
- Faculty of Medicine and Health
- The University of Sydney
- Australia
- Heart Research Institute
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Bortot M, Ashworth K, Sharifi A, Walker F, Crawford NC, Neeves KB, Bark D, Di Paola J. Turbulent Flow Promotes Cleavage of VWF (von Willebrand Factor) by ADAMTS13 (A Disintegrin and Metalloproteinase With a Thrombospondin Type-1 Motif, Member 13). Arterioscler Thromb Vasc Biol 2019; 39:1831-1842. [DOI: 10.1161/atvbaha.119.312814] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Objective—
Acquired von Willebrand syndrome is defined by excessive cleavage of the VWF (von Willebrand Factor) and is associated with impaired primary hemostasis and severe bleeding. It often develops when blood is exposed to nonphysiological flow such as in aortic stenosis or mechanical circulatory support. We evaluated the role of laminar, transitional, and turbulent flow on VWF cleavage and the effects on VWF function.
Approach and Results—
We used a vane rheometer to generate laminar, transitional, and turbulent flow and evaluate the effect of each on VWF cleavage in the presence of ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type-1 motif, member 13). We performed functional assays to evaluate the effect of these flows on VWF structure and function. Computational fluid dynamics was used to estimate the flow fields and forces within the vane rheometer under each flow condition. Turbulent flow is required for excessive cleavage of VWF in an ADAMTS13-dependent manner. The assay was repeated with whole blood, and the turbulent flow had the same effect. Our computational fluid dynamics results show that under turbulent conditions, the Kolmogorov scale approaches the size of VWF. Finally, cleavage of VWF in this study has functional consequences under flow as the resulting VWF has decreased ability to bind platelets and collagen.
Conclusions—
Turbulent flow mediates VWF cleavage in the presence of ADAMTS13, decreasing the ability of VWF to sustain platelet adhesion. These findings impact the design of mechanical circulatory support devices and are relevant to pathological environments where turbulence is added to circulation.
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Affiliation(s)
- Maria Bortot
- From the Department of Pediatrics (M.B., K.A., F.W., K.B.N., D.B., J.D.P.), University of Colorado Anschutz Medical Campus, Aurora
- Department of Bioengineering (M.B., K.B.N.), University of Colorado Anschutz Medical Campus, Aurora
| | - Katrina Ashworth
- From the Department of Pediatrics (M.B., K.A., F.W., K.B.N., D.B., J.D.P.), University of Colorado Anschutz Medical Campus, Aurora
| | - Alireza Sharifi
- Department of Mechanical Engineering (A.S., D.B.), Colorado State University, Fort Collins
| | - Faye Walker
- From the Department of Pediatrics (M.B., K.A., F.W., K.B.N., D.B., J.D.P.), University of Colorado Anschutz Medical Campus, Aurora
| | - Nathan C. Crawford
- Department of Material Characterization, Thermo Fisher Scientific, Madison, WI (N.C.C.)
| | - Keith B. Neeves
- From the Department of Pediatrics (M.B., K.A., F.W., K.B.N., D.B., J.D.P.), University of Colorado Anschutz Medical Campus, Aurora
- Department of Bioengineering (M.B., K.B.N.), University of Colorado Anschutz Medical Campus, Aurora
| | - David Bark
- From the Department of Pediatrics (M.B., K.A., F.W., K.B.N., D.B., J.D.P.), University of Colorado Anschutz Medical Campus, Aurora
- Department of Mechanical Engineering (A.S., D.B.), Colorado State University, Fort Collins
- School of Biomedical Engineering (D.B.), Colorado State University, Fort Collins
| | - Jorge Di Paola
- From the Department of Pediatrics (M.B., K.A., F.W., K.B.N., D.B., J.D.P.), University of Colorado Anschutz Medical Campus, Aurora
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Rowlands GW, Good BC, Deutsch S, Manning KB. Characterizing the HeartMate II Left Ventricular Assist Device Outflow Using Particle Image Velocimetry. J Biomech Eng 2018; 140:2677750. [DOI: 10.1115/1.4039822] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Indexed: 11/08/2022]
Abstract
Ventricular assist devices (VADs) are implanted in patients with a diseased ventricle to maintain peripheral perfusion as a bridge-to-transplant or as destination therapy. However, some patients with continuous flow VADs (e.g., HeartMate II (HMII)) have experienced gastrointestinal (GI) bleeding, in part caused by the proteolytic cleavage or mechanical destruction of von Willebrand factor (vWF), a clotting glycoprotein. in vitro studies were performed to measure the flow located within the HMII outlet cannula under both steady and physiological conditions using particle image velocimetry (PIV). Under steady flow, a mock flow loop was used with the HMII producing a flow rate of 3.2 L/min. The physiological experiment included a pulsatile pump operated at 105 BPM with a ventricle filling volume of 50 mL and in conjunction with the HMII producing a total flow rate of 5.0 L/min. Velocity fields, Reynolds normal stresses (RNSs), and Reynolds shear stresses (RSSs) were analyzed to quantify the outlet flow's potential contribution to vWF degradation. Under both flow conditions, the HMII generated principal Reynolds stresses that are, at times, orders of magnitude higher than those needed to unfurl vWF, potentially impacting its physiological function. Under steady flow, principal RNSs were calculated to be approximately 500 Pa in the outlet cannula. Elevated Reynolds stresses were observed throughout every phase of the cardiac cycle under physiological flow with principal RNSs approaching 1500 Pa during peak systole. Prolonged exposure to these conditions may lead to acquired von Willebrand syndrome (AvWS), which is accompanied by uncontrollable bleeding episodes.
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Affiliation(s)
- Grant W. Rowlands
- Department of Biomedical Engineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802
| | - Bryan C. Good
- Department of Biomedical Engineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802
| | - Steven Deutsch
- Department of Biomedical Engineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802
| | - Keefe B. Manning
- Professor Department of Biomedical Engineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802
- Department of Surgery, Penn State Hershey Medical Center, Hershey, PA 17033 e-mail:
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Molteni A, Masri ZPH, Low KWQ, Yousef HN, Sienz J, Fraser KH. Experimental measurement and numerical modelling of dye washout for investigation of blood residence time in ventricular assist devices. Int J Artif Organs 2018; 41:201-212. [DOI: 10.1177/0391398817752877] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ventricular assist devices have become the standard therapy for end-stage heart failure. However, their use is still associated with severe adverse events related to the damage done to the blood by fluid dynamic stresses. This damage relates to both the stress magnitude and the length of time the blood is exposed to that stress. We created a dye washout technique which combines experimental and numerical approaches to measure the washout times of ventricular assist devices. The technique was used to investigate washout characteristics of three commercially available and clinically used ventricular assist devices: the CentriMag, HVAD and HeartMate II. The time taken to reach 5% dye concentration at the outlet (T05) was used as an indicator of the total residence time. At a typical level of cardiac support, 5 L/min and 100 mmHg, T05 was 0.93, 0.28 and 0.16 s for CentriMag, HVAD and HeartMate II, respectively, and increased to 5.06, 1.64 and 0.96 s for reduced cardiac support of 1 L/min. Regional variations in washout characteristics are described in this article. While the volume of the flow domain plays a large role in the differences in T05 between the ventricular assist devices, after standardising for ventricular assist device volume, the secondary flow path was found to increase T05 by 35%. The results explain quantitatively, for the first time, why the CentriMag, which exerts low shear stress magnitude, has still been found to cause acquired von Willebrand Syndrome in patients.
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Affiliation(s)
| | - Zubair PH Masri
- Department of Mechanical Engineering, University of Bath, Bath, UK
| | - Kenny WQ Low
- Advanced Sustainable Manufacturing Technologies (ASTUTE) 2020 Operation, College of Engineering, Swansea University, Swansea, UK
| | - Haitham N Yousef
- Advanced Sustainable Manufacturing Technologies (ASTUTE) 2020 Operation, College of Engineering, Swansea University, Swansea, UK
| | - Johann Sienz
- Advanced Sustainable Manufacturing Technologies (ASTUTE) 2020 Operation, College of Engineering, Swansea University, Swansea, UK
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