scholarly journals Computational Fontan Analysis: Preserving accuracy while expediting workflow

2021 ◽  
Author(s):  
Xiaolong Liu ◽  
Seda Aslan ◽  
Byeol Kim ◽  
Linnea Warburton ◽  
Derrick Jackson ◽  
...  
Keyword(s):  
Particle Filtering ◽  
Cfd Simulation ◽  
Fontan Operation ◽  
Flow Distribution ◽  
Mesh Size ◽  
Computational Time ◽  
Patient Specific ◽  
Flow Loop ◽  
Cfd Simulations

Background: Post-operative outcomes of the Fontan operation have been linked to graft shape after implantation. Computational fluid dynamics (CFD) simulations are used to explore different surgical options. The objective of this study is to perform a systematic in vitro validation for investigating the accuracy and efficiency of CFD simulation to predict Fontan hemodynamics. Methods: CFD simulations were performed to measure indexed power loss (iPL) and hepatic flow distribution (HFD) in 10 patient-specific Fontan models, with varying mesh and numerical solvers. The results were compared with a novel in vitro flow loop setup with 3D printed Fontan models. A high-resolution differential pressure sensor was used to measure the pressure drop for validating iPL predictions. Microparticles with particle filtering system were used to measure HFD. The computational time was measured for a representative Fontan model with different mesh sizes and numerical solvers. Results: When compared to in vitro setup, variations in CFD mesh sizes had significant effect on HFD (p = 0.0002) but no significant impact on iPL (p = 0.069). Numerical solvers had no significant impact in both iPL (p = 0.50) and HFD (P = 0.55). A transient solver with 0.5 mm mesh size requires computational time 100 times more than a steady solver with 2.5 mm mesh size to generate similar results. Conclusions: The predictive value of CFD for Fontan planning can be validated against an in vitro flow loop. The prediction accuracy can be affected by the mesh size, model shape complexity and flow competition.

PIV-Measured Versus CFD-Predicted Flow Dynamics in Anatomically Realistic Cerebral Aneurysm Models

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Matthew D. Ford ◽  
Hristo N. Nikolov ◽  
Jaques S. Milner ◽  
Stephen P. Lownie ◽  
Edwin M. DeMont ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Cardiac Cycle ◽  
Flow Dynamics ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Flow Loop ◽  
Cfd Simulations ◽  
Flow Through

Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement between PIV and CFD suggests that CFD can reliably predict the details of the intra-aneurysmal flow dynamics observed in anatomically realistic in vitro models. Nevertheless, given the various modeling assumptions, this does not prove that they are mimicking the actual in vivo hemodynamics, and so validations against in vivo data are encouraged whenever possible.

Prediction of Blood Flow Distribution in Liver Radioembolization Using Convolutional Neural Networks

2020 ◽  
Author(s):  
Amirtahà Taebi ◽  
Catherine T. Vu ◽  
Emilie Roncali
Keyword(s):  
Blood Flow ◽  
Cfd Simulation ◽  
Mean Squared Error ◽  
Flow Distribution ◽  
Homogeneous Distribution ◽  
Blood Flow Distribution ◽  
Cfd Simulations ◽  
Squared Error ◽  
Network Output ◽  
Yttrium 90

Abstract We have developed a new dosimetry approach, called CFDose, for liver cancer radioembolization based on computational fluid dynamics (CFD) simulation in the hepatic arterial tree. Although CFDose overcomes some of the limitations of the current dosimetry methods such as the unrealistic assumption of homogeneous distribution of yttrium-90 in the liver, it suffers from the expensive computational cost of CFD simulations. To accelerate CFDose, we introduce a deep learning model to predict the blood flow distribution between the liver segments in a patient with hepatocellular carcinoma. The model was trained with the results of CFD simulations under different outlet boundary conditions. The model consisted of convolutional, average pooling and transposed convolution layers. A regression layer with a mean-squared-error loss function was utilized at the network output to estimate the arterial outlet blood flow. The mean-squared error and prediction accuracy were calculated to measure model performance. Results showed that the average difference between the CFD results and predicted flow data was less than 2.45% for all the samples in the test dataset. The proposed model thus estimated the blood flow distribution with high accuracy significantly faster than a CFD simulation. The network output can be used to estimate the yttrium-90 dose distribution in the liver in future studies.

A Hemodynamic Comparison of Myocardial Bridging and Coronary Atherosclerotic Stenosis: A Computational Model with Experimental Evaluation

2020 ◽  
Author(s):  
Mohammadali Sharzehee ◽  
Yasamin Seddighi ◽  
Eugene A. Sprague ◽  
Ender A. Finol ◽  
Hai-Chao Han
Keyword(s):  
Pressure Drop ◽  
Experimental Results ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Flow Loop ◽  
Myocardial Bridging ◽  
Atherosclerotic Stenosis ◽  
Stenosis Severity ◽  
The Difference

Abstract Myocardial bridging (MB) and coronary atherosclerotic stenosis can impair coronary blood flow and may cause myocardial ischemia or even stoke. It remains unclear how MB and stenosis are similar or different regarding their impacts on coronary hemodynamics. The purpose of this study was to compare the hemodynamic effects of MB and stenosis using experimental and computational fluid dynamics (CFD) approaches. For CFD modeling, three MB patients with different levels of lumen obstruction such as mild, moderate, and severe were selected. Patient-specific left anterior descending coronary artery models were reconstructed from biplane angiograms. For each MB patient, the virtually healthy and stenotic models were also simulated for comparison. In addition, an in vitro flow-loop was developed to evaluate the model-predicted pressure drop. The CFD modeling results demonstrated that the difference between MB and stenosis increased with increasing MB/stenosis severity and flow rate. Experimental results showed that increasing the MB length (by 140%) only had significant impact on the pressure drop in the severe MB (39% increase at the exercise). However, increasing the stenosis length dramatically increased the pressure drop in both moderate and severe stenoses at all flow rates (31% and 93% increase at the exercise, respectively). Both CFD and experimental results confirmed that the MB had a higher maximum and a lower mean pressure drop in comparison with the stenosis, regardless of MB/stenosis severity. A better understanding of MB and stenosis may improve the therapeutic strategies in coronary disease patients and prevent acute coronary syndromes.

Design, Development and Temporal Evaluation of an MRI-Compatible In-Vitro Circulation Model Using a Compliant AAA Phantom

2021 ◽  
Author(s):  
Mirunalini Thirugnanasambandam ◽  
Tejas Canchi ◽  
Senol Piskin ◽  
Christof Karmonik ◽  
Ethan Kung ◽  
...  
Keyword(s):  
Circulation Model ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Design Development ◽  
Dynamics Modeling ◽  
Flow Loop ◽  
Volume Changes ◽  
Essential Components

Abstract Biomechanical characterization of abdominal aortic aneurysms (AAA) has become commonplace in rupture risk assessment studies. However, its translation to the clinic has been greatly limited due to the complexity associated with its tools and their implementation. The unattainability of patient-specific tissue properties leads to the use of generalized population-averaged material models in finite element analyses, which adds a degree of uncertainty to the wall mechanics quantification. In addition, computational fluid dynamics modeling of AAA typically lacks the patient-specific inflow and outflow boundary conditions that should be obtained by non-standard of care clinical imaging. An alternative approach for analyzing AAA flow and sac volume changes is to conduct in vitro experiments in a controlled laboratory environment. We designed, built, and characterized quantitatively a benchtop flow-loop using a deformable AAA silicone phantom representative of a patient-specific geometry. The impedance modules, which are essential components of the flow-loop, were fine-tuned to ensure typical intra-sac pressure conditions. The phantom was imaged with a magnetic resonance imaging (MRI) scanner to acquire time-resolved images of the moving wall and the velocity field inside the sac. Temporal AAA sac volume changes lead to a corresponding variation in compliance throughout the cardiac cycle. The primary outcome of this work was the design optimization of the impedance elements, the quantitative characterization of the resistive and capacitive attributes of a compliant AAA phantom, and the exemplary use of MRI for flow visualization and quantification of the deformed AAA geometry.

scholarly journals In-Vitro Validation of Self-Powered Fontan Circulation for Treatment of Single Ventricle Anomaly

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 401
Author(s):  
Arka Das ◽  
Ray Prather ◽  
Eduardo Divo ◽  
Michael Farias ◽  
Alain Kassab ◽  
...  
Keyword(s):  
Flow Rate ◽  
Experimental Testing ◽  
Fontan Operation ◽  
Fontan Circulation ◽  
Lumped Parameter Model ◽  
Pressure Reduction ◽  
Flow Loop ◽  
Pulmonary Flow ◽  
Self Powered

Around 8% of all newborns with a Congenital Heart Defect (CHD) have only a single functioning ventricle. The Fontan operation has served as palliation for this anomaly for decades, but the surgery entails multiple complications, and the survival rate is less than 50% by adulthood. A rapidly testable novel alternative is proposed by creating a bifurcating graft, or Injection Jet Shunt (IJS), used to “entrain” the pulmonary flow and thus provide assistance while reducing the caval pressure. A dynamically scaled Mock Flow Loop (MFL) has been configured to validate this hypothesis. Three IJS nozzles of varying diameters 2, 3, and 4 mm with three aortic anastomosis angles and pulmonary vascular resistance (PVR) reduction have been tested to validate the hypothesis and optimize the caval pressure reduction. The MFL is based on a Lumped-Parameter Model (LPM) of a non-fenestrated Fontan circulation. The best outcome was achieved with the experimental testing of a 3 mm IJS by producing an average caval pressure reduction of more than 5 mmHg while maintaining the clinically acceptable pulmonary flow rate (Qp) to systemic flow rate (Qs) ratio of ~1.5. Furthermore, alteration of the PVR helped in achieving higher caval pressure reduction with the 3 mm IJS at the expense of an increase in Qp/Qs ratio.

scholarly journals A Simulation Study of Drying Chamber for Marine Product

2021 ◽  
Vol 13 (6) ◽  
Author(s):  
Mohd Afzanizam Mohd Rosli ◽  
◽  
Hiew Sit Jing ◽  
Nur Izzati Mohd Azhar ◽  
Maidi Saputra ◽  
...  
Keyword(s):  
Steady State ◽  
Cfd Simulation ◽  
Air Flow ◽  
Flow Distribution ◽  
Cfd Simulations ◽  
High Quality ◽  
Steady State Condition ◽  
Temperature Distributions ◽  
Marine Product ◽  
Drying Chamber

Drying chamber is a drying application for agriculture product to produce high quality and hygiene product. The purpose of this paper is to propose best configuration trays arrangement in drying chamber for better distribution of velocity and temperature. Therefore, five configurations of trays are analyzed to obtain the best performance of uniformity air flow distribution within drying chamber. CFD simulation studied the uniform air flow in the drying chamber in steady state condition. A validation is performed by comparing the data obtained from the literature review CFD simulation to ensure the methodology is correct. Then, the drying chamber with different trays arrangements are simulated using CFD simulations to obtain velocity and temperature distributions at nine plotted points on trays. From the results obtained, it concluded that design (A) and (D) are selected as the best designs for uniformity because there is less discrepancy for each point contributed the more uniformity of distribution.

Abstract 1122‐000014: Effects of Patient‐Specific Blood Properties and Inflow Conditions on Hemodynamics in Cerebral Aneurysms

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Yuya Uchiyama ◽  
Hiroyuki Takao ◽  
Soichiro Fujimura ◽  
Takashi Suzuki ◽  
Yuma Yamanaka ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Parent Artery ◽  
Computational Domain ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Visual Evaluation ◽  
The Mean ◽  
Inflow Conditions

Introduction : Computational Fluid Dynamics (CFD) simulation is an effective tool to investigate pathologies and clinical outcomes of cerebral aneurysms from the hemodynamic perspective. However, simulation conditions such as the blood properties and boundary conditions are usually referred to in the literature do not consider patient‐specific values. In this study, we measured blood properties and extracted the inflow conditions from four‐dimensional digital subtraction angiography (4D‐DSA) images for patients who underwent flow diverter (FD) deployment. Then, we conducted CFD simulations considering the deployed FD geometry to investigate the effect of patient‐specific conditions on aneurysmal hemodynamics. Methods : We took whole blood samples of five patients with intracranial aneurysms just before the surgery and measured the blood density and viscosity with a densitometer and a falling needle rheometer. The patients underwent 4D‐DSA imaging, from which we calculated the patient‐specific inflow velocity of each patient using an in‐house flow extraction program. We used in‐house virtual FD deployment software to reproduce the FD geometry for each patient. We then defined the computational domain including the FD geometry. Four CFD simulations were performed for each of the five patients: (1) a steady CFD simulation under a referred Newtonian blood model and previously published inflow conditions as a basic simulation pattern (2) a CFD simulation including the patient‐specific non‐Newtonian blood properties only, (3) a CFD simulation including the inflow conditions only, and (4) a CFD simulation including both the patient‐specific blood properties and inflow conditions. We calculated the mean velocity in the aneurysm normalized by the mean velocity in the parent artery and the wall shear stress (WSS) of the aneurysm. We compared the results of the four CFD simulations and calculated their differences based on the values for the basic simulation pattern. Results : Based on the visual evaluation, the flow structures of the four CFD simulation patterns differed only slightly from each other, but a quantitative comparison revealed that there were large differences in the hemodynamic parameters. For the velocity, there was an average 14.2% difference with the steady CFD simulation results when the patient‐specific blood properties are considered, and an average 35.8% difference when the patient‐specific inflow conditions are considered. There was an average 60.7% difference when both the patient‐specific blood properties and inflow conditions are taken into account. For the WSS, there was an average 8.75% difference when including the patient‐specific blood properties and an average 66.8% difference in including the patient‐specific inflow conditions. There was an average 69.3% difference in including both conditions are considered. It appeared that the effect of including patient‐specific inflow conditions was more substantial than that of including the patient‐specific blood properties, and most robust when both conditions were included. Conclusions : The hemodynamics obtained from CFD simulations with the deployed FD appears to strongly depend on both the blood properties and the inflow conditions. This result implies that CFD simulations with the referred conditions may not accurately reproduce the hemodynamics. It was confirmed that patient‐specific conditions should be included in CFD simulations.

CFD Simulation of Prediction of Pressure Drop in Venturi Scrubber

2012 ◽  
Vol 166-169 ◽  
pp. 3008-3011 ◽  
Author(s):  
Majid Ali ◽  
Chang Qi Yan ◽  
Zhong Ning Sun ◽  
Jian Jun Wang ◽  
Khurram Mehboob
Keyword(s):  
Fluid Dynamics ◽  
Pressure Drop ◽  
Cfd Simulation ◽  
Mesh Size ◽  
Cfd Simulations ◽  
Venturi Scrubber ◽  
Severe Accidents ◽  
Ansys Cfx ◽  
Simulation Results ◽  
Accuracy Of Results

Venturi Scrubbers are used in filtered vented containment system (FVCS) for collection of aerosols produced in NPP in severe accidents. Therefore, venturi scrubber (VS) needs an attention to design it properly and improved in all aspects. In this research, CFD simulations of prediction of pressure drop in venturi scrubber has been carried out. ANSYS CFX tool is used to obtain the simulation results. k-ε turbulence model is employed to study the fluid dynamics of the venturi scrubber. Mesh size plays an important role for convergence and accuracy of results. Therefore, the mesh independency is checked for optimized mesh size.

Abstract 15923: A Combined In Silico and In Vitr o Approach for Surgical Planning of Pediatric Coarctation Repair

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Fanette Chassagne ◽  
Sujatha Buddhe ◽  
Lester C Permut ◽  
David MCMULLAN ◽  
Stephen P Seslar ◽  
...  
Keyword(s):  
Surgical Treatment ◽  
Aortic Arch ◽  
In Silico ◽  
Cfd Simulation ◽  
Patch Repair ◽  
Recirculation Region ◽  
Patient Specific ◽  
Congenital Cardiac Malformation

Introduction: Coarctation of the aorta is a congenital malformation of the proximal descending aorta that results in severe narrowing of the vessel lumen. It causes significant changes in the aortic hemodynamics, including reduced blood flow and an increased pressure gradient in this area of the vasculature. When this congenital cardiac malformation is associated with aortic arch hypoplasia, a two step-surgery is proposed: first, an end-to-end anastomosis in performed to remove all the ductal tissue surrounding the coarctation, and then the aorta is longitudinally incised and patched to increase its diameter. The design of the patch, based on the surgeon’s experience, is done in the OR. A combined in silico and in vitro approach is proposed to test the possibility of a priori design of the patch. This approach would also open the door to optimization of the patch to restore physiological hemodynamics in the aorta. Methods & Results: CFD simulations of the hemodynamics in the pre-treatment aortic arch were created from the segmentation of patients’ images who received surgical treatment at Seattle Children’s Hospital. In vivo hemodynamics data were used as boundary conditions for the simulation. The design of the patch was created via an in-house code and was based on surgeons’ input: the locations of the start and the end of the lumen enlargement and the length of the aortic segment to be resected. The optimization of the patch design was performed by comparing the simulated hemodynamics (pressure drop, endothelial shear stress, size of the recirculation region, ...) before and after the patch repair. The optimized patch design was then used by the surgeon to perform the in vitro surgical treatment on a physical model of the patient’s anatomy, made in a translucent silicon rubber. The repaired anatomical model was scanned by X-ray microtomography and cast in an optically clear silicone. Time-resolved particle image velocimetry measurements were performed to characterize the post-treatment hemodynamics, and compared to the results of the CFD simulation. Conclusions: This unique in silico and in vitro approach allows surgeons to perform different repairs on patient-specific physical in vitro models and to optimize the design of the patch prior to starting the surgery.

Improvement of Cavitation Surge in a Double Suction Centrifugal Pump by Use of CFD

2017 ◽  
Author(s):  
Shusaku Kagawa ◽  
Naoki Matsushita
Keyword(s):  
Centrifugal Pump ◽  
Cfd Simulation ◽  
Reverse Flow ◽  
Low Frequency ◽  
The Other ◽  
Computational Time ◽  
Complete Suppression ◽  
Cavitation Model ◽  
Cfd Simulations ◽  
Pump Impeller

This paper discussed about suppressions of cavitation surge in a double suction centrifugal pump. In order to suppress the cavitation surge, CFD simulation was carried out. Cavitation surge was observed near the best efficiency point, and it was difficulty to operate the pump stably. The specific speed of the tested pump was about 81 [m3/min, min−1, m] or 533 [ft., USGPM, min.−1]. In general, the main cause of the cavitation surge is inlet reverse flows at the impeller inlet. In order to prevent the inlet reverse flow, two kinds of modification at the impeller inlet were applied. One was the reduction of impeller inlet area by using a suction ring, and the other was the reduction of impeller inlet diameter. To reduce the computational time, in CFD model, a half of the double suction centrifugal pump was modeled. CFD simulations were carried out using ANSYS CFX with the Rayleigh Preset cavitation model. It was confirmed that the head fluctuation caused by the cavitation phenomena was predicted qualitatively by use of unsteady CFD simulation in the original pump impeller. The head fluctuation was about the 16% of the time averaged head and the very low frequency was confirmed by the FFT analysis. In addition, the relationship between head characteristics and cavitation behavior was observed clearly. The objective of the suction ring was to eliminate the head fluctuations caused by the cavitation. It was concluded that the suction ring was very effective to prevent the cavitation surge. On the other hand, the decrease of impeller inlet diameter was effective to reduce the head fluctuations, which became half of that for the original pump impeller. As a result, it was suggested that the complete suppression of the cavitation surge by the reduction of impeller inlet diameter was difficult in this case. It was concluded that unsteady CFD simulations with cavitation model is very effective for clarification of the impeller inlet modification on the cavitation surge.

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