Computational fluid dynamics study in biomedical applications: a review
01 Jan 2016-
TL;DR: The essential methodology of CFD as a reliable tool for researchers and medical scientist in understanding the physiology and pathophysiology of cardiovascular system and respiratory system through simulation is discussed.
Abstract: Computational Fluid Dynamics (CFD) is a widely adopted methodology of computer-based simulation in order to solve complex problems in many modern engineering fields as well as biomedical field. CFD is becoming a key component in developing updated designs and optimization through computational simulations, resulting in lower operating costs with enhanced efficiency. Even though biomedical application is pertaining to the complexity of human anatomy and human body fluid behaviour, the recent CFD in biomedical application is more accessible and practicable due to the availability of high performance hardware and software with advances in computer sciences. Many simulations and clinical results have been used to study the analyses in biomedical applications, particularly in blood flow and nasal airflow. The study of blood flow analysis includes the circulation of blood of ventricle function, coronary artery and heart valves. Meanwhile, the nasal airflow analysis consists of the basic airflow in human nose, drug delivery improvement and virtual surgery. Therefore, this review discusses the essential methodology of CFD as a reliable tool for researchers and medical scientist in understanding the physiology and pathophysiology of cardiovascular system and respiratory system through simulation. CFD plays a major role as a decision support prior to undertaking a real commitment to execute any medical design alterations and provide the direction to develop medical interventions.
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TL;DR: The proposed mathematical modelling shows that the deteriorating WSS is an indicator for possible rupture and its value oscillates over a cardiac cycle as well as over different stress conditions, which provides good insight of TAA.
Abstract: An attempt has been made to evaluate the effects of wall shear stress (WSS) on thoracic aortic aneurysm (TAA) using Computational Fluid Dynamics (CFD). Aneurysm is an excessive localized swelling of the arterial wall due to many physiological factors and it may rupture causing shock or sudden death. The existing imaging modalities such as MRI and CT assist in the visualization of anomalies in internal organs. However, the expected dynamic behaviour of arterial bulge under stressed condition can only be effectively evaluated through mathematical modelling. In this work, a 3D aneurysm model is reconstructed from the CT scan slices and eventually the model is imported to Star CCM+ (Siemens, USA) for intensive CFD analysis. The domain is discretized using polyhedral mesh with prism layers to capture the weakening boundary more accurately. When there is flow reversal in TAA as seen in the velocity vector plot, there is a chance of cell damage causing clots. This is because of the shear created in the system due to the flow pattern. It is observed from the proposed mathematical modelling that the deteriorating WSS is an indicator for possible rupture and its value oscillates over a cardiac cycle as well as over different stress conditions. In this model, the vortex formation pattern and flow reversals are also captured. The non-Newtonian model, including a pulsatile flow instead of a steady average flow, does not overpredict the WSS (15.29 Pa compared to 16 Pa for the Newtonian model). Although in a cycle the flow behaviour is laminar-turbulent-laminar (LTL), utilizing the non-Newtonian model along with LTL model also overpredicted the WSS with a value of 20.1 Pa. The numerical study presented here provides good insight of TAA using a systematic approach to numerical modelling and analysis.
21 citations
Cites background or methods from "Computational fluid dynamics study ..."
...[15] detailed the recent usage of CFD in biomedical applications....
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...It is desirable that y+ be in this range to ensure that the physics of boundary layer are truly represented in this study’s computation even though standard Figure 4: Velocity profile graph [15]....
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...The velocity profile was obtained from the published literature [15]....
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TL;DR: The results of this study indicated a tradeoff that exists between the attainable density and velocity of the microjet on the skin surface with variation in nozzle diameter; the optimum nozzle diameter was found to be within 200-250 μm under the present conditions.
14 citations
01 Jan 2020
TL;DR: CFD will become ubiquitous but will be buried inside digital twins/reduced order models so that it is usable by engineers, whereas CFD experts will be more engaged in creating them using high fidelity computations and of course, in extending the application of CFD into diverse areas of human activity.
Abstract: Computational Fluid Dynamics appears to be poised on the threshold of rapid advances powered by the recent developments in deep machine learning. Deep machine learning will be used to improve the speed, accuracy and, the user-friendliness of CFD software. The applications of CFD will expand beyond the usual aerospace and mechanical/thermal areas to include areas such as biomedical, sport, food processing, environmental, fire safety, buildings ventilation and energy efficiency, and a host of other areas of social relevance. Deep machine learning will be routinely used to generate digital twins/reduced order models which will have a profound impact on the way that CFD is utilized. Standardized interfaces will be developed to embed the digital twins into CAD/PLM software and even spreadsheets. This will enable engineers to rapidly assimilate these models into the product development process and thereby create optimal designs, without needing the services of a CFD expert. These models will also be used for optimal control. In addition, these models can be combined with experimental and field data using Internet-of-Things (IoT) to provide for real-time monitoring of the device and assessing the need for preventive maintenance, etc. This has profound implications for product safety in the field. The social benefits are obvious. In short, CFD will become ubiquitous but will be buried inside digital twins/reduced order models so that it is usable by engineers, whereas CFD experts will be more engaged in creating them using high fidelity computations and of course, in extending the application of CFD into diverse areas of human activity.
7 citations
TL;DR: Dp16 mice can be a useful model to examine the pathophysiology of increased upper airway collapsibility of DS and to evaluate the efficacy of therapeutic interventions for breathing and sleep anomalies, according to a combination of computational fluid dynamics and micro-CT imaging.
Abstract: A high prevalence of obstructive sleep apnea (OSA) has been reported in Down syndrome (DS) owing to the coexistence of multiple predisposing factors related to its genetic abnormality, posing a challenge for the management of OSA. We hypothesized that DS mice recapitulate craniofacial abnormalities and upper airway obstruction of human DS and can serve as an experimental platform for OSA research. This study, thus, aimed to quantitatively characterize the upper airway as well as craniofacial abnormalities in Dp(16)1Yey (Dp16) mice. Dp16 mice demonstrated craniofacial hypoplasia, especially in the ventral part of the skull and the mandible, and rostrally positioned hyoid. These changes were accompanied with a shorter length and smaller cross-sectional area of the upper airway, resulting in a significantly reduced upper airway volume in Dp16 mice. Our non-invasive approach, a combination of computational fluid dynamics and high-resolution micro-CT imaging, revealed a higher negative pressure inside the airway of Dp16 mice compared to wild-type littermates, showing the potential risk of upper airway collapse. Our study indicated that Dp16 mice can be a useful model to examine the pathophysiology of increased upper airway collapsibility of DS and to evaluate the efficacy of therapeutic interventions for breathing and sleep anomalies.
6 citations
TL;DR: In this paper , the authors have focused on unsteady nanofluid flow over a bidirectional stretching surface in the presence and absence of a magnetic field respectively and applied similarity transformation to convert the governing equations, from PDE to nonlinear ordinary type.
Abstract: This research has focused on unsteady nanofluid flow over a bidirectional stretching surface in the presence and absence of a magnetic field respectively. The direction of the magnetic field is vertically upwards. Nonlinear sort of thermal radiation has been considered here. Additionally, Brownian motion and thermophoresis are revealing an innovative way in this investigation. Moreover, we captured flow characteristics and temperature distribution along realistic thermal and mass convective boundary conditions. Similarity transformation is applied to convert the governing equations, from PDE to nonlinear ordinary type. Using RK4 shooting criteria through MAPLE 17 software we have solved numerically this transformed leading equation along with boundary conditions with the required accuracy rate. Upshots are explored with appropriate geometrical representation and tables. After those physical consignments as Sherwood number, Nusselt number also skin friction have been calculated. It has to remark from consequences that fluid velocity along x -axis, temperature, volume fraction are declined along with the positive increment of stretching parameter while the opposite impact is perceived for the velocity of nanofluid towards y − direction. The transportation of heat in nanoliquid increases for enlarging radiation factor also this effect turns advanced when magnetic force is neglected.
5 citations
References
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Book•
01 Jun 1995
TL;DR: This chapter discusses the development of the Finite Volume Method for Diffusion Problems, a method for solving pressure-Velocity Coupling in Steady Flows problems, and its applications.
Abstract: *Introduction. *Conservation Laws of Fluid Motion and Boundary Conditions. *Turbulence and its Modelling. *The Finite Volume Method for Diffusion Problems. *The Finite Volume Method for Convection-Diffusion Problems. *Solution Algorithms for Pressure-Velocity Coupling in Steady Flows. *Solution of Discretised Equations. *The Finite Volume Method for Unsteady Flows. *Implementation of Boundary Conditions. *Advanced topics and applications. Appendices. References. Index.
7,412 citations
"Computational fluid dynamics study ..." refers background in this paper
...Nevertheless, it is becoming more accessible and practicable by virtue of the advent of digital computer with high performance hardware and software[2]....
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...The applications of CFD received tremendous attention and widely adopted for solving complex problems in various modern engineering fields including electronics packaging, chemical engineering, turbines, external and internal environmental architectural design, marine and environmental engineering, metrology, hydrology and biomedical engineering [2,3]....
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Book•
09 Nov 2007
TL;DR: The only course text available that is specifically designed to give an applications lead, software oriented approach to understanding and using CFD is as discussed by the authors, which is coupled with a complete grounding in the necessary mathematical principles of CFD.
Abstract: A senior level undergraduate and graduate textbook for a wide audience of engineering students taking a first course in CFD or Computer Aided Engineering. Fully course matched, with the most extensive and rigorous pedagogy and features of any book in the field. The first book in the field aimed at CFD users rather than developers. The only course text available that is specifically designed to give an applications lead, software oriented approach to understanding and using CFD. This is coupled with a complete grounding in the necessary mathematical principles of CFD. Unlike existing books this has not been written with the needs of advanced students who are expected to develop their own CFD code in mind. The widespread availability of commercial software enables this book to meet the needs of beginner CFD students who use commercial software. Meets the needs of students taking a wide range of courses. Unlike existing titles it does not focus on the needs of advanced aerospace or applied math courses. Ideal for use on the burgeoning courses in mechanical, automotive, marine, environmental, civil and chemical engineering that harness CFD or computer aided engineering more generally.The strongest pedagogy of any available book. Core mathematics are developed in a step by step fashion, with no assumed steps left out in order to develop a solid understanding of the conservation laws, mathematical transport equations and basic concepts of fluid mechanics and heat transfer that comprise the key to effective use of CFDDetailed worked examples reinforce learning and link to the real applications students will work with; end of chapter knowledge check exercises, homework assignment questions, plus separate Instructor's Manual
682 citations
"Computational fluid dynamics study ..." refers background in this paper
...The applications of CFD received tremendous attention and widely adopted for solving complex problems in various modern engineering fields including electronics packaging, chemical engineering, turbines, external and internal environmental architectural design, marine and environmental engineering, metrology, hydrology and biomedical engineering [2,3]....
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TL;DR: General agreement of gross flow features were found that included high velocities in the constrictive nasal valve area region, high flow close to the septum walls, and vortex formations posterior to the nasal valve and olfactory regions.
210 citations
"Computational fluid dynamics study ..." refers background in this paper
...Wen et al.[16] also simulated steady laminar nasal airflow for flow rate of 7.5 to 15 L/min to present flow patterns between the left and right nasal cavities by adopting CFD simulation software (FLUENT) and CT scan images of human nasal cavity models....
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...Wen et al.[16] also simulated steady laminar nasal airflow for flow rate of 7....
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TL;DR: Good agreement between measured and numerically computed total pressure drops observed up to a flow rate of 250 ml/s is an important step to validate the ability of CFD software to describe flow in a physiologically realistic binasal model.
Abstract: Pressure-flow relationships measured in human plastinated specimen of both nasal cavities and maxillary sinuses were compared to those obtained by numerical airflow simulations in a numerical three-dimensional reconstruction issued from CT scans of the plastinated specimen. For experiments, flow rates up to 1,500 ml/s were tested using three different gases: HeO(2), Air, and SF(6). Numerical inspiratory airflow simulations were performed for flow rates up to 353 ml/s in both the nostrils using a finite-volume-based method under steady-state conditions with CFD software using a laminar model. The good agreement between measured and numerically computed total pressure drops observed up to a flow rate of 250 ml/s is an important step to validate the ability of CFD software to describe flow in a physiologically realistic binasal model. The major total pressure drop was localized in the nasal valve region. Airflow was found to be predominant in the inferior median part of nasal cavities. Two main vortices were observed downstream from the nasal valve and toward the olfactory region. In the future, CFD software will be a useful tool for the clinician by providing a better understanding of the complexity of three-dimensional breathing flow in the nasal cavities allowing more appropriate management of the patient's symptoms.
135 citations
TL;DR: It is suggested that significant inter-individual differences exist in bulk airflow patterns in the nose as well as streamlines and velocity magnitudes predicted by the computational model.
Abstract: Differences in nasal anatomy among human subjects may cause significant differences in respiratory airflow patterns and subsequent dosimetry of inhaled gases and particles in the respiratory tract. This study used computational fluid dynamics (CFD) to study inter-individual differences in nasal airflow among four healthy individuals. Magnetic resonance imaging (MRI) scans were digitized and nasal-surface-area-to-volume ratios (SAVR) were calculated for 15 adults. Two males and two females, representative of the range of SAVR values, were selected for flow analysis. Nasal CFD models were constructed for each subject by a semi-automated process that provided input to a commercial mesh generator to generate structured hexahedral meshes (Gambit, Fluent, Inc., Lebanon, NH, USA). Steady-state inspiratory laminar airflow at 15 L/min was calculated using commercial CFD software (FIDAP, Fluent, Inc., Lebanon, NH, USA). Streamline patterns, velocities, and helicity values were compared. In all subjects, the majority of flow passed through the middle and ventral regions of the nasal passages; however, the amount and location of swirling flow differed among individuals. Cross-sectional flow allocation analysis also indicated inter-individual differences. Laboratory water–dye experiments confirmed streamlines and velocity magnitudes predicted by the computational model. These results suggest that significant inter-individual differences exist in bulk airflow patterns in the nose.
81 citations