scholarly journals Pulsatile Aortic Blood Flow - a Critical Assessment of Boundary Conditions

2020 ◽  
Author(s):  
Alexander Fuchs ◽  
Niclas Berg ◽  
Lisa Prahl Wittberg
Keyword(s):  
Blood Flow ◽  
Boundary Conditions ◽  
Patient Specific ◽  
Aortic Blood Flow ◽  
Relative Residence Time ◽  
Heart Cycle ◽  
Simulation Results ◽  
Inlet Conditions ◽  
Set Up ◽  
Outflow Boundary

Abstract Patient specific (PS) blood flow studies have become popular in recent years but have thus far had limited clinical impact. This is possibly due to uncertainties and errors in the underlying models and simulations set-up. This study focuses on the sensitivity of simulation results due to in- and outflow boundary conditions (BC:s). Nine different inlet- and seven different outlet BC:s were applied to two variants of a healthy subject's thoracic aorta. Temporal development of the flow is essential for the formation and development of helical/spiralling flow where the commonly observed clockwise helical motion may change direction during the heart-cycle. The sensitivity to temporal and spatial variations in the inlet conditions is significant both when expressed in terms of mean and maximal wall shear stress (WSS) and its different averaged variables, e.g. Time-Averaged WSS (TAWSS), Oscillating Shear Index (OSI) and Relative Residence Time (RRT). The simulation results are highly sensitive to BC. For example, the maximal WSS the results may vary over 3 orders of magnitude (1 to 1000 Pa) depending on particular combinations of BC:s. Moreover, certain formulations of outlet boundary conditions may be inconsistent of the computed flow field if the underlying assumptions of the space-time dependence are violated. The results of this study show that CFD simulations can reveal flow details that can enhance understanding of blood flows. However, the results also demonstrate the potential difficulties in mimicking blood flow in clinical situations.

Computational Study on the Effects of Peripheral Vessel Network on Blood Flow in the Arterial Circle of Willis

2007 ◽  
Author(s):  
Shigefumi Tokuda ◽  
Takeshi Unemura ◽  
Marie Oshima
Keyword(s):  
Numerical Simulation ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Vascular System ◽  
Computational Study ◽  
Circulatory System ◽  
Biological Data ◽  
Patient Specific ◽  
Peripheral Vessel

Cerebrovascular disorder such as subarachnoid hemorrhage (SAH) is 3rd position of the cause of death in Japan [1]. Its initiation and growth are reported to depend on hemodynamic factors, particularly on wall shear stress or blood pressure induced by blood flow. In order to investigate the information on the hemodynamic quantities in the cerebral vascular system, the authors have been developing a computational tool using patient-specific modeling and numerical simulation [2]. In order to achieve an in vivo simulation of living organisms, it is important to apply appropriate physiological conditions such as physical properties, models, and boundary conditions. Generally, the numerical simulation using a patient-specific model is conducted for a localized region near the research target. Although the analysis region is only a part of the circulatory system, the simulation has to include the effects from the entire circulatory system. Many studies have carried out to derive the boundary conditions to model in vivo environment [3–5]. However, it is not easy to obtain the biological data of cerebral arteries due to head capsule.

Computational Modeling of Shear-Based Hemolysis Caused by Renal Obstruction

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Polina A. Segalova ◽  
K. T. Venkateswara Rao ◽  
Christopher K. Zarins ◽  
Charles A. Taylor
Keyword(s):  
Blood Flow ◽  
Boundary Conditions ◽  
Renal Artery ◽  
Aortic Aneurysms ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Shear Stresses ◽  
Baseline Model ◽  
Implantable Medical Devices ◽  
Renal Obstruction

As endovascular treatment of abdominal aortic aneurysms (AAAs) gains popularity, it is becoming possible to treat certain challenging aneurysmal anatomies with endografts relying on suprarenal fixation. In such anatomies, the bare struts of the device may be placed across the renal artery ostia, causing partial obstruction to renal artery blood flow. Computational fluid dynamics (CFD) was used to simulate blood flow from the aorta to the renal arteries, utilizing patient-specific boundary conditions, in three patient models and calculate the degree of shear-based blood damage (hemolysis). We used contrast-enhanced computed tomography angiography (CTA) data from three AAA patients who were treated with a novel endograft to build patient-specific models. For each of the three patients, we constructed a baseline model and endoframe model. The baseline model was a direct representation of the patient’s 30-day post-operative CTA data. This model was then altered to create the endoframe model, which included a ring of metallic struts across the renal artery ostia. CFD was used to simulate blood flow, utilizing patient-specific boundary conditions. Pressures, flows, shear stresses, and the normalized index of hemolysis (NIH) were quantified for all patients. The overall differences between the baseline and endoframe models for all three patients were minimal, as measured though pressure, volumetric flow, velocity, and shear stress. The average NIH across the three baseline and endoframe models was 0.002 and 0.004, respectively. Results of CFD modeling show that the overall disturbance to flow caused by the presence of the endoframe struts is minimal. The magnitude of the NIH in all models was well below the accepted design and safety threshold for implantable medical devices that interact with blood flow.

Tuning a Multiscale Model of Abdominal Aortic Hemodynamics to Incorporate Patient-Specific Features of Flow and Pressure Waveforms

2009 ◽  
Author(s):  
Ryan L. Spilker ◽  
Charles A. Taylor
Keyword(s):  
Boundary Conditions ◽  
Computational Models ◽  
Multiscale Model ◽  
Patient Specific ◽  
Vascular Walls ◽  
Outflow Boundary Conditions ◽  
Abdominal Aortic ◽  
Cardiovascular Models ◽  
Outflow Boundary ◽  
Aortic Hemodynamics

Computational models enable the calculation of quantities that are impractical or impossible to measure and the prediction of physiological changes due to interventions. In order to be useful, cardiovascular models must be both rooted in physical principles and designed such that measured or otherwise desired features of the cardiovascular system are reproduced. The former requirement has motivated the development of image-based anatomic models, patient-specific inflow boundary conditions, deformable vascular walls, outflow boundary conditions that represent the influence of the downstream circulation, and multiscale models. The development of approaches to address the latter requirement, reproducing desired features of the circulation, is a critical area of modeling research that has received comparatively little attention.

scholarly journals Vascular flow simulations using SimVascular and OpenFOAM

2021 ◽  
Author(s):  
Swetha Yogeswaran ◽  
Fei Liu
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Open Source ◽  
Open Source Software ◽  
Flow Analysis ◽  
Coarctation Of The Aorta ◽  
Patient Specific ◽  
Specific Information ◽  
Imaging Data ◽  
Set Up

AbstractApplications of computational fluid dynamics (CFD) techniques to aid in the diagnosis and treatment of cardiovascular disease have entered the research domain in recent years, due to their ability to provide valuable patient-specific information without risks associated with highly invasive procedures. SimVascular [1] [2] is an open-source software which allows streamlined processing and CFD blood flow analysis of medical imaging data. OpenFOAM [3] is a proven open-source software which allows for versatile modeling of various fluid dynamics phenomena. In this study, both SimVascular and OpenFOAM simulations are set up with identical computational mesh, similar numerical schemes, boundary conditions, and material properties, to model blood flow in the coronary artery of a 10 year old patient with Coarctation of the Aorta (CoA) who underwent end-to-side anastomosis. Difference in the flow fields such as flow rate, pressure, vorticity, and wall shear stress between SimVascular and OpenFOAM are analyzed. Similar results are obtained in both simulations up to a certain model time, before the results become drastically different. Both the similarities and differences are documented and discussed.

The Vascular Model Repository: A Public Resource of Medical Imaging Data and Blood Flow Simulation Results

2013 ◽  
Author(s):  
Nathan M. Wilson ◽  
Ana K. Ortiz ◽  
Allison B. Johnson
Keyword(s):  
Blood Flow ◽  
Treatment Options ◽  
Unmet Need ◽  
Flow Simulation ◽  
Image Data ◽  
Patient Specific ◽  
Imaging Data ◽  
Medical Software ◽  
Public Resource ◽  
Simulation Results

Patient-specific blood flow simulations may provide insight into disease progression, treatment options, and medical device design that would be difficult or impossible to obtain experimentally. However, publicly available image data and computer models for researchers and device designers are extremely limited. The NHLBI sponsored Open Source Medical Software Corporation (Contracts No: HHSN268200800008C & HHSN268201100035C) and its university collaborators to build a public repository including realistic, image-based anatomic models and related hemodynamic simulation results to address this unmet need.

Volumetric Flow at the Supraceliac and Infrarenal Levels in Patients With Abdominal Aortic Aneurysm: Waveforms and Allometric Scaling Relationships

2009 ◽  
Author(s):  
Andrea S. Les ◽  
Janice J. Yeung ◽  
Phillip M. Young ◽  
Robert J. Herfkens ◽  
Ronald L. Dalman ◽  
...  
Keyword(s):  
Blood Flow ◽  
Abdominal Aortic Aneurysm ◽  
Aortic Aneurysm ◽  
Boundary Conditions ◽  
Computational Simulation ◽  
Critical Role ◽  
Healthy Person ◽  
Patient Specific ◽  
Hemodynamic Forces ◽  
Abdominal Aortic

Hemodynamic forces are thought to play a critical role in abdominal aortic aneurysm (AAA) formation and growth, as well as in the migration and failure of aortic stent grafts. Computational simulation of blood flow enables the study of such hemodynamic forces; however, these simulations require accurate geometries and boundary conditions, usually in the form of flow and pressure data at specific locations. Although hundreds of computed tomography (CT) and magnetic resonance (MR) imaging studies of AAA geometry are performed daily in the clinical setting, flow information is difficult to obtain: It is not possible to reliably measure flow using CT, and while phase-contrast MRI (PC-MRI) can measure velocities, it is rarely used clinically for AAA patients. As a result, many AAA blood flow simulations use highly resolved patient-specific geometries, but may utilize literature-derived flows for inlet boundary conditions from a single, unrelated, sometimes healthy person of dissimilar body mass.

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