scholarly journals Methodology for Computational Fluid Dynamic Validation for Medical Use: Application to Intracranial Aneurysm

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Nikhil Paliwal ◽  
Robert J. Damiano ◽  
Nicole A. Varble ◽  
Vincent M. Tutino ◽  
Zhongwang Dou ◽  
...  
Keyword(s):  
Flow Field ◽  
Intracranial Aneurysm ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Model Error ◽  
Patient Specific ◽  
Cfd Validation ◽  
Validation Data ◽  
Promising Tool ◽  
Simulation Results

Computational fluid dynamics (CFD) is a promising tool to aid in clinical diagnoses of cardiovascular diseases. However, it uses assumptions that simplify the complexities of the real cardiovascular flow. Due to high-stakes in the clinical setting, it is critical to calculate the effect of these assumptions in the CFD simulation results. However, existing CFD validation approaches do not quantify error in the simulation results due to the CFD solver’s modeling assumptions. Instead, they directly compare CFD simulation results against validation data. Thus, to quantify the accuracy of a CFD solver, we developed a validation methodology that calculates the CFD model error (arising from modeling assumptions). Our methodology identifies independent error sources in CFD and validation experiments, and calculates the model error by parsing out other sources of error inherent in simulation and experiments. To demonstrate the method, we simulated the flow field of a patient-specific intracranial aneurysm (IA) in the commercial CFD software star-ccm+. Particle image velocimetry (PIV) provided validation datasets for the flow field on two orthogonal planes. The average model error in the star-ccm+ solver was 5.63 ± 5.49% along the intersecting validation line of the orthogonal planes. Furthermore, we demonstrated that our validation method is superior to existing validation approaches by applying three representative existing validation techniques to our CFD and experimental dataset, and comparing the validation results. Our validation methodology offers a streamlined workflow to extract the “true” accuracy of a CFD solver.

scholarly journals A Closed-Loop Optimized System with CFD Data for Liquid Maldistribution Model

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1332
Author(s):  
Wei Zhang ◽  
Liyi Li ◽  
Baoping Zhang ◽  
Xin Xu ◽  
Jian Zhai ◽  
...  
Keyword(s):  
Closed Loop ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Structural Parameters ◽  
Computational Cost ◽  
Pso Algorithm ◽  
Oil Refining ◽  
Support Vector ◽  
Cfd Validation ◽  
Liquid Distributor

For the simulation of a trickle-bed reactor (TBR) in coal and oil refining, modeling the liquid maldistribution of the gas-liquid distributor incurs enormous pre-processing work and bears a huge computational cost. A closed-loop optimized system with computational fluid dynamic (CFD) data is therefore proposed for the first time in this paper. A fast prediction model based on support vector regression (SVR) is developed to simplify the modeling of the liquid flow rate in TBRs. The model uses CFD simulation results to determine an optimized set of structural parameters for the gas-liquid distributor in TBRs. In order to obtain an accurate SVR model quickly, the particle swarm optimization (PSO) algorithm is employed to optimize the SVR parameters. Then, the structural parameters corresponding to the minimum liquid maldistribution factor are calculated using the response surface methodology (RSM) based on the hybrid PSO-SVR model. The CFD validation results show a good agreement with the values predicted by RSM, with liquid maldistribution factors of 0.159 and 0.162, respectively.

scholarly journals Development of an Intravascular Doppler Optical Coherence Tomography Imaging Technique for Neurovascular Applications

2021 ◽  
Author(s):  
Barry Vuong
Keyword(s):  
Blood Flow ◽  
Optical Coherence Tomography ◽  
Intracranial Aneurysm ◽  
Intracranial Aneurysms ◽  
Fluid Dynamic ◽  
Patient Specific ◽  
Optical Coherence ◽  
Specific Flow ◽  
Arterial Lumen ◽  
Risk Of Rupture

The rupture of an intracranial aneurysm can cause spontaneous subarachnoid hemorrhage and result in sudden death. A large portion of intracranial aneurysms occurs near the center of the head, at the skull base, which poses significant technical challenge to neurosurgeons due to limited accessibility. The utilization of angiography is prominent during the treatment of intracranial aneurysms. However, malapposition of stent or incomplete packing of the intracranial aneurysm can be difficult to assess with angiography, and could lead to severe postoperative complications. As a result, angiography may not be sufficient in determining the risk of rupture as the compensatory mechanisms are known to occur at the microstructural level due to the local hemodynamics in the arterial lumen, as well as in evaluating the intraoperative treatment. In this work, we describe a method for assessing intracranial aneurysm through the evaluation of blood flow within the lumen and morphological structures of the arterial wall with optical coherence tomography (OCT). Sterile intravascular fiber-optic catheters can be introduced in the artery to detect blood flow. Prior to this work, limited investigations of catheter based Doppler OCT (DOCT) were reported. A novel signal processing technique was developed to further reduce the effect of Doppler noise within a catheter based DOCT system. This technique consisted of splitting the interferogram of an OCT signal prior to estimating the Doppler shift. This split spectrum DOCT (ssDOCT) method was evaluated through flow models and porcine models, as well as through the correlation between ssDOCT algorithm and computational fluid dynamic (CFD) models. It was observed that ssDOCT provided improved Doppler artefact suppression over the conventional DOCT technique. ssDOCT also provided the ability to estimate lower velocities within the DOCT image to measure the hemodynamic patterns around stent struts in both the internal carotid and patient specific flow phantoms. An OCT imaging study was also conducted consisting of surgically resected human intracranial aneurysms. Further enhancement of the detection of these key morphological structures was demonstrated by an optical-attenuation imaging variant of OCT. The presented techniques could provide further insights to the cause of intracranial aneurysm rupture and vascular healing mechanisms.

scholarly journals Development of an Intravascular Doppler Optical Coherence Tomography Imaging Technique for Neurovascular Applications

2021 ◽  
Author(s):  
Barry Vuong
Keyword(s):  
Blood Flow ◽  
Optical Coherence Tomography ◽  
Intracranial Aneurysm ◽  
Intracranial Aneurysms ◽  
Fluid Dynamic ◽  
Patient Specific ◽  
Optical Coherence ◽  
Specific Flow ◽  
Arterial Lumen ◽  
Risk Of Rupture

The rupture of an intracranial aneurysm can cause spontaneous subarachnoid hemorrhage and result in sudden death. A large portion of intracranial aneurysms occurs near the center of the head, at the skull base, which poses significant technical challenge to neurosurgeons due to limited accessibility. The utilization of angiography is prominent during the treatment of intracranial aneurysms. However, malapposition of stent or incomplete packing of the intracranial aneurysm can be difficult to assess with angiography, and could lead to severe postoperative complications. As a result, angiography may not be sufficient in determining the risk of rupture as the compensatory mechanisms are known to occur at the microstructural level due to the local hemodynamics in the arterial lumen, as well as in evaluating the intraoperative treatment. In this work, we describe a method for assessing intracranial aneurysm through the evaluation of blood flow within the lumen and morphological structures of the arterial wall with optical coherence tomography (OCT). Sterile intravascular fiber-optic catheters can be introduced in the artery to detect blood flow. Prior to this work, limited investigations of catheter based Doppler OCT (DOCT) were reported. A novel signal processing technique was developed to further reduce the effect of Doppler noise within a catheter based DOCT system. This technique consisted of splitting the interferogram of an OCT signal prior to estimating the Doppler shift. This split spectrum DOCT (ssDOCT) method was evaluated through flow models and porcine models, as well as through the correlation between ssDOCT algorithm and computational fluid dynamic (CFD) models. It was observed that ssDOCT provided improved Doppler artefact suppression over the conventional DOCT technique. ssDOCT also provided the ability to estimate lower velocities within the DOCT image to measure the hemodynamic patterns around stent struts in both the internal carotid and patient specific flow phantoms. An OCT imaging study was also conducted consisting of surgically resected human intracranial aneurysms. Further enhancement of the detection of these key morphological structures was demonstrated by an optical-attenuation imaging variant of OCT. The presented techniques could provide further insights to the cause of intracranial aneurysm rupture and vascular healing mechanisms.

Abstract P304: A Novel Method for Modeling Flow in Cerebral Vasculature Diagnostics

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Huy Dinh
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Physiological Saline ◽  
Patient Specific ◽  
Cfd Analysis ◽  
Velocity Data ◽  
Flow Measurements ◽  
Flow Parameters ◽  
Flow Pressure ◽  
Dependent Flow

Introduction: We examined the viability of pairing wire-obtained flow pressure data with computational fluid dynamic (CFD) analysis for accurate patient-specific 3D reconstruction of flow through cerebral vessels—an approach that provides comprehensive velocity data and other flow parameters to assist the preventative diagnosis of cerebral stenosis. Methods: Two physical phantom models of a cerebral stenosis—differing in regard to vascular morphology at and around the stenosis—were prepared, filled with physiological saline and connected individually to a flow pump (Vascular Simulations LLC Left Heart Replicator) applying pulsatile flow. Pressure measurements were taken upstream of the stenosis by microcatheter-guided wires to define an inlet boundary condition for CFD analysis. Pressure and velocity at 2 cm proximal to stenosis, the stenosis inlet, the stenosis outlet, and 2 cm distal to stenosis were measured to validate the CFD simulated flow. Results: Excellent agreement was observed between CFD and wire-measured time-dependent flow pressure, with the expected pulsatile behavior observed at each location. Between the two methods, differences in maximum systolic pressures ranged between |0.73±0.72|% and |3.90±0.74|%. Differences in minimum diastolic pressures ranged between |1.79±1.33|% and |9.08±1.42|%. Velocity data from wire measurements lacked pulsatile behavior and showed differences ranging between |2.93±5.20|% and |120.10±2.91|% from CFD-obtained measurements, which did show correct pulsatile behavior. Larger discrepancies were strongly associated with areas of higher CFD predicted velocities (r=0.86). Conclusion: Guidewire flow measurements provided CFD analysis with accurate inlet boundary conditions and validated CFD simulation results. CFD analysis allowed for detailed visualization of key flow parameters that may be difficult to physically measure—such as velocity—that are relevant for understanding risk factors associated with cerebral stenosis on a case-by-case basis.

CFD Simulation of Incompressible Turbomachinery — A Comparison of Results From ANSYS Fluent and OpenFOAM

2014 ◽  
Author(s):  
Franziska Bothe ◽  
Christian Friebe ◽  
Martin Heinrich ◽  
Rüdiger Schwarze
Keyword(s):  
Flow Field ◽  
Energy Efficient ◽  
Total Pressure ◽  
High Performance ◽  
Cfd Simulation ◽  
Pressure Rise ◽  
Wake Flow ◽  
Ansys Fluent ◽  
Simulation Results ◽  
Good Agreement

A numerical investigation of incompressible turbomachinery and the comparison of two CFD packages are presented within this paper. A ducted single rotor fan is simulated with OpenFOAM and ANSYS FLUENT by applying methods as comparable as possible. The characteristic maps and flow fields are analyzed and the results from the CFD codes are compared to examine differences regarding accuracy and efficiency. Additionally the influence of the turbulence model is determined. It is found that the CFD programs show a good agreement especially at the machines design point. The information about the flow field of this fan is used for the modelling of a high-performance and energy-efficient ducted contra-rotating fan (CRF). Comparing the CRF simulation results to those of the single rotor fan, a doubling of the total pressure rise and a significant reduction of the swirl in the wake flow can be noticed.

scholarly journals Analisis Perbedaan Mesh Pada Simulasi Boiler PLTGU Tanjung Priok Berbasis CFD

Jurnal METTEK ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 46
Author(s):  
I Nyoman Agus Adi Saputra ◽  
I Gusti Bagus Wijaya Kusuma ◽  
I Gusti Ngurah Priambadi
Keyword(s):  
Computational Fluid Dynamic ◽  
Cfd Simulation ◽  
Initial Conditions ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Process Stage ◽  
Convergence Study ◽  
Simulation Results ◽  
Gas Power Plant ◽  
Meshing Process

Penelitian Analisis Perbedaan Mesh berbasis Computational Fluid Dynamic (CFD) ini dilakukan Pada Boiler PLTGU Tanjung Priok. Boiler atau reboiler dalam sistem PLTGU dikategorikan sebagai alat penukar kalor karena perpindahan panasnya dilakukan tanpa kontak langsung antara media pemanas dengan media yang dipanaskan. Fluida kerja pada boiler PLTGU Tanjung Priok berupa gas methane dan air. Penelitian ini bertujuan melihat jumlah pembagian elemen terhadap hasil simulasi dengan menggunakan dua model Studi konvergensi grid yaitu dengan grid kasar, dan yang paling optimal melalui hasil simulasi CFD. Metode yang digunakan mulai dari mendesain geometri boiler sesuai kondisi di lapangan menginput initial conditions dan  boundry conditions. Data hasil penelitian yang sudah di lakukan pada simulasi boiler menunjukkan bahwa baik temperatur, tekanan dan kecepatan aliran memiliki nilai yang sama besar dan tidak di pengaruhi oleh pembagian elemen yang di lakukan pada saat proses meshing dari elemen yang paling kasar dengan jumlah total sebanyak 203.363 sampai pada tahap  proses meshing dengan elemen teroptimal yang berjumlah sebanyak 1.491.428 berdasarkan hal tersebut maka proses simulasi yang dilakukan menjadi lebih efisien karena proses perhitungan data dari elemen yang lebih sedikit mendapatkan hasil yang sama dengan elemen yang lebih banyak. The research on Mesh Difference Analysis based on Computational Fluid Dynamic (CFD) was conducted at Tanjung Priok PLTGU Boiler. Boilers or reboilers in PLTGU systems are categorized as heat exchangers because the heat transfer is done without direct contact between the heating media and the heated media. The working fluid in the Tanjung Priok gas power plant boiler is in the form of methane gas and water. This study aims to look at the number of elements divided against the simulation results by using two grid convergence study models, namely with a coarse grid, and the most optimal through CFD simulation results. The method used starts from designing the boiler geometry according to the field conditions, inputting initial conditions and boundry conditions. Data from research that has been done on boiler simulations shows that both temperature, pressure and flow velocity have the same value and are not affected by the division of elements carried out during the meshing process of the most coarse elements with a total number of 203.363 up to the meshing process stage with the optimum elements totaling 1,491,428 based on this, the simulation process carried out becomes more efficient because the process of calculating data from fewer elements gets the same results with more elements.

scholarly journals Computational Fluid Dynamics Simulation of Airflow and Air Pattern in the Living Room for Reducing Coronavirus Exposure

2021 ◽  
Author(s):  
Majid Bayatian ◽  
Khosro Ashrafi ◽  
Zahra Amiri ◽  
Elahe Jafari
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Indoor Air ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Dynamics Simulation ◽  
Living Room ◽  
Air Velocity ◽  
Cfd Validation ◽  
Airflow Pattern

Abstract Viruses can be transmitted in indoor environments. Important factors in Indoor Air Quality (IAQ) are air velocity, relative humidity, temperature, and airflow pattern and Computational fluid dynamics (CFD) can use for IAQ assessment. The objective of this study is to CFD simulation in the living room to the prediction of the air pattern and air velocity. A computational fluid dynamic model was applied for airflow pattern and air velocity simulation. For simulation, GAMBIT, FLUENT, and CFD post software were used as preprocessing, processing, and post-processing, respectively. CFD validation was carried out by comparing the computed data with the experimental measurements. The final mesh number was set to 1,416,884 elementary cells and SIMPLEC algorithm was used for pressure-velocity coupling. PERSTO, and QUIK schemes have been used for the pressure terms, and the other variables, respectively. Simulations were carried out in ACH equals 3, 6 and 8 in four lateral walls. The maximum error and root mean square error from the air velocity were 14% and 0.10, respectively. Terminal settling velocity and relaxation time were equal to 0.302 ×10− 2 m/s and 0.0308 ×10− 2 s for 10 µm diameter particles, respectively. The stopping distance was 0.0089m and 0.011m for breathing and talking, respectively. The maximum of mean air velocity is in scenario 4 with ACH = 8 that mean air velocity is equal to 0.31 in 1.1m height, respectively. The results of this study showed that avoiding family gatherings is necessary for exposure control and suitable airflow and pattern can be improving indoor air conditions.

scholarly journals Development of an Intravascular Doppler Optical Coherence Tomography Imaging Technique for Neurovascular Applications

2021 ◽  
Author(s):  
Barry Vuong
Keyword(s):  
Blood Flow ◽  
Optical Coherence Tomography ◽  
Intracranial Aneurysm ◽  
Intracranial Aneurysms ◽  
Fluid Dynamic ◽  
Patient Specific ◽  
Optical Coherence ◽  
Specific Flow ◽  
Arterial Lumen ◽  
Risk Of Rupture

The rupture of an intracranial aneurysm can cause spontaneous subarachnoid hemorrhage and result in sudden death. A large portion of intracranial aneurysms occurs near the center of the head, at the skull base, which poses significant technical challenge to neurosurgeons due to limited accessibility. The utilization of angiography is prominent during the treatment of intracranial aneurysms. However, malapposition of stent or incomplete packing of the intracranial aneurysm can be difficult to assess with angiography, and could lead to severe postoperative complications. As a result, angiography may not be sufficient in determining the risk of rupture as the compensatory mechanisms are known to occur at the microstructural level due to the local hemodynamics in the arterial lumen, as well as in evaluating the intraoperative treatment. In this work, we describe a method for assessing intracranial aneurysm through the evaluation of blood flow within the lumen and morphological structures of the arterial wall with optical coherence tomography (OCT). Sterile intravascular fiber-optic catheters can be introduced in the artery to detect blood flow. Prior to this work, limited investigations of catheter based Doppler OCT (DOCT) were reported. A novel signal processing technique was developed to further reduce the effect of Doppler noise within a catheter based DOCT system. This technique consisted of splitting the interferogram of an OCT signal prior to estimating the Doppler shift. This split spectrum DOCT (ssDOCT) method was evaluated through flow models and porcine models, as well as through the correlation between ssDOCT algorithm and computational fluid dynamic (CFD) models. It was observed that ssDOCT provided improved Doppler artefact suppression over the conventional DOCT technique. ssDOCT also provided the ability to estimate lower velocities within the DOCT image to measure the hemodynamic patterns around stent struts in both the internal carotid and patient specific flow phantoms. An OCT imaging study was also conducted consisting of surgically resected human intracranial aneurysms. Further enhancement of the detection of these key morphological structures was demonstrated by an optical-attenuation imaging variant of OCT. The presented techniques could provide further insights to the cause of intracranial aneurysm rupture and vascular healing mechanisms.

scholarly journals CFD Simulation of Thermal-Hydraulic Benchmark V1000CT-2 Using ANSYS CFX

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
Thomas Höhne
Keyword(s):  
Best Practice ◽  
Nuclear Reactor ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Turbulence Models ◽  
Measured Data ◽  
Reactor Power ◽  
Cfd Validation ◽  
Relative Temperature ◽  
Water Reactors

Plant measured data from VVER-1000 coolant mixing experiments were used within the OECD/NEA and AER coupled code benchmarks for light water reactors to test and validate computational fluid dynamic (CFD) codes. The task is to compare the various calculations with measured data, using specified boundary conditions and core power distributions. The experiments, which are provided for CFD validation, include single loop cooling down or heating-up by disturbing the heat transfer in the steam generator through the steam valves at low reactor power and with all main coolant pumps in operation. CFD calculations have been performed using a numerical grid model of 4.7 million tetrahedral elements. The Best Practice Guidelines in using CFD in nuclear reactor safety applications has been used. Different advanced turbulence models were utilized in the numerical simulation. The results show a clear sector formation of the affected loop at the downcomer, lower plenum and core inlet, which corresponds to the measured values. The maximum local values of the relative temperature rise in the calculation are in the same range of the experiment. Due to this result, it is now possible to improve the mixing models which are usually used in system codes.

Research of 3D-CFD Simulation on a Large Sized Pit Type Carburizing Furnace

2006 ◽  
Vol 118 ◽  
pp. 337-342
Author(s):  
Wei Min Zhang ◽  
Ye Ma ◽  
Lin Lin Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Cfd Simulations ◽  
3 Dimensional ◽  
Set Up ◽  
Carburizing Process

A fluid dynamic model was set up to describe the flow field of gas in a large sized pit type carburizing furnace when large sized gears were being carburized. The commercial software Fluent was adopted to carry out 3 dimensional computational fluid dynamics (3D-CFD) simulations of the gas flow field under different, actually four kinds of , furnace designs in this article. The flow fields of the carburizing gas around the part were analyzed. According to the simulations and analysis, it was shown that the number of fans on gear’s carburizing is not a primary factor, using a air inducting tub can improve the carburizing process significantly and proper loading tray design can also be positive. The results indicate that the simulation provides a reference to the furnace’s design optimization.

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