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Long-term exposure to risk factors will lead to coronary atherosclerosis, which will lead to the formation and progression of coronary plaque. Early identification of high-risk plaque characteristics will help prevent plaque rupture or erosion, thus avoiding the occurrence of acute cardiovascular events. Biomechanical stress plays an important role in progression and rupture of atherosclerotic plaques. In recent years, non-invasive coronary computed tomography angiography (CCTA) computational fluid dynamics (CFD) modeling has made it possible to acquire the corresponding biomechanical stress parameters. These coronary biomechanical stress parameters, especially wall shear stress (WSS), will aid in the development of a more accurate clinical model for predicting plaque progression and major adverse cardiovascular events ( MACE ). In this review, the biomechanical stress and the role of WSS from CCTA in atherosclerosis were introduced, and the researches on the relationship between biomechanical stress from CCTA and coronary artery diseases were discussed.
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Objective To investigate the effects of banding width on hemodynamic characteristics of pulmonary artery (PA) by constructing pulmonary artery banding (PAB) models with different widths. Methods Based on clinical practice, with the same banding position and degree, computer-aided design (CAD) was utilized to reconstruct three-dimensional PAB models with different banding widths (2, 3, 4, 5 mm). Hemodynamic characteristics of the models with different banding widths, including pressure, streamlines, energy loss, energy efficiency and blood flow distribution ratio, were compared and analyzed through computational fluid dynamics (CFD). Results The pressure of PA decreased significantly, while the change of banding width had no significant effects on the pressure drop level at banding position. With the increase of banding width, the energy loss decreased, and the energy efficiency showed an upward trend. The blood flow of the left PA raised, and the ratio of blood flow distribution between the left PA and right PA increased, with the maximum reaching up to 2.28 : 1. Conclusions The increase of banding width can reduce the energy loss of PA and improve the energy efficiency of blood flow, but it will lead to the imbalance of blood flow distributions between the left and right lungs. Both the balance of blood flow distribution and the energy loss should be considered in choice for banding width of PAB. The virtual design of PAB surgery based on CAD and CFD will assist individualized banding width selection in future.
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Objective To explore hemodynamics of the aortic arch and supraarch vessels after thoracic endovascular aortic repair with fenestration and parallel grafts techniques, and compare the differences of these techniques. Methods Four patients with aortic arch lesions whose supraarch vessels were reconstructed by different surgical techniques (fenestration, chimney and periscope) were studied, and three-dimensional (3D) geometric models were established based on postoperative image data. The physiological flow obtained from two dimensional (2D) phase contrast magnetic resonance imaging were imposed on the ascending aorta inlet and the supraarch vessels outlets. The pressure waveform of 3-element Windkessel model was imposed on the descending aorta outlet. Through computational fluid dynamics ( CFD ) simulations, the hemodynamic parameters were obtained, including the pressure of supraarch vessels, the velocity vector of the stent inlet, and the relative residence time. Results The pressure change of the periscope stent was the largest, followed by the fenestration stent, and the pressure change of the chimney stent was the smallest. The velocity of the fenestration and periscope stent inlet was uneven, which might form vortex. The velocity of the chimney stent inlet was even. The high relative residence time concentrated in distal end of the fenestration stent outer wall, the ‘gutter’ part, and the place where the chimney and periscope stent adhered to the vessel wall. Conclusions The pressure difference between the inner and outer walls of the fenestration and periscope stent was high, so it was recommended to use the balloon-expandable stent. The pressure difference between the inner and outer walls of the chimney stent was low, so it was recommended to use the self-expanding stent. The predicted location of thrombosis was consistent with the clinical follow-up data, so it may be used for surgical planning and risk assessment of interventional treatment of aortic arch lesions.
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After more than 100 years of development， spray drying technology has become more mature and widely used， and it is of great importance in the field of traditional Chinese medicine （TCM）. TCM powders prepared by spray drying is the raw material of dispensing granules， and the powder properties have an important influence on subsequent molding process and product quality. As a new form of TCM， dispensing granules have been included in the management category of TCM decoction pieces， indicating a broader application market， and a consensus has also been reached on the importance of TCM powder research. Based on this， the author summarized the application progress of spray drying in the study of TCM powders， including the factors affecting spray drying process， such as liquid properties， process parameters and equipment factors， as well as the application of computational fluid dynamics （CFD） and thermodynamic model in spray drying process simulation. Moreover， some commonly used pharmaceutical excipients for the modification of TCM powders were also introduced such as maltodextrin， microcrystalline cellulose and povidone. In addition， spray drying technology can also be used as a preparation technology for new drug delivery systems such as microcapsules and solid dispersions. Through the summary of this paper， the author suggests that the future research direction of spray drying of TCM can be carried out from the aspects of application rule of the coprocessing auxiliary materials based on the "unification of medicines and excipients"， the "structure-property" relationship of spray-dried powders and the application of computer simulation and design， so as to further enrich the application of spray drying in the field of TCM powders.
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Objective To explore the relationship between the establishment of collateral circulation caused by iliac vein compression syndrom(IVCS) and the deep venous thrombosis (DVT). Methods Different types of ideal collateral circulation models and IVCS patient-specific models were numerically simulated using computational fluid dynamics (CFD) in combination with the blood stasis model. The relationship between blood retention and collateral types and cross-sectional area was studied, and the relationship with thrombosis was explored. Results Wall shear stress (WSS) at the distal end part of each ideal model was 0.3 Pa. After four cardiac cycles, the residual blood stayed at the stenosis and the distal end part for the lumbar ascending and pelvic type models, the old blood volume fraction (OBVF) varied with collateral cross-sectional areas, ranging from 5%-90% and 70%-80%, respectively. The OBVF of the coexistence model was above 80%. The WSS at the distal end part of the patient-specific model was 0.9 Pa, and the OBVF at the distal end part was 51.5%. Conclusions The stenosis and the distal end part are most prone to blood stasis, and closely related with DVT. The larger the collateral cross-sectional area, the more serious the blood stagnation. Blood stagnation of the coexistence model is higher compared with the model with lumbar ascending type and pelvic type.
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Objective In view of the situation that tracheal atrophy causes the overall airway size to become smaller in the elderly, effects of the airway wall surface on reconstruction of a narrow airway and the airflow field under different respiratory conditions were investigated. Methods A three-dimensional (3D) model of human airway was established by using Mimics, and flow field in the airway was simulated by computational fluid dynamics (CFD) method. The inner wall pressure and the distribution of airflow were analyzed and compared under different breathing states. Results Under different respiratory states, the pressure of endotracheal wall was relatively uniform in the endotracheal wall, but decreased significantly in air inlet of the bronchial stenosis segment, and reached negative pressure near the narrowest area. The airflow velocity decreased from the center of the pipe to the boundary layer, and the velocity reached the maximum at the narrow area. Vortex was generated when airflow passed through the narrow area, and the larger the inlet flow velocity was, the larger the positive pressure and negative pressure were, the more obvious the pressure drop at the narrow area was, and the more obvious the vortex phenomenon was. Conclusions The constriction of the airway stenosis area caused by negative pressure will lead to the patient’s dyspnea, and the eddy current will cause the airway wall to be affected by the aerodynamic shear stress and may damage the airway wall mucosa. Therefore, understanding of the pressure distribution and velocity distribution in the narrow airway can provide references for clinical diagnosis and treatment of such diseased airways.
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Objective To explore hemodynamic performance of the aortic dissection after lesions, so as to provide a more scientific basis for patient treatment. Methods Based on computed tomography angiography (CTA) image data from a patient with complex Stanford B-type aortic dissection, the personalized aortic dissection models with different rupture shapes (H-type, O-type, and V-type) at proximal end of the aortic dissection were established. Combined with computational fluid dynamics (CFD) and morphological analysis method, distributions of the velocity at rupture section, the blood flow, the wall pressure and the wall shear stress (WSS) were analyzed. Results The flow velocity, the highest pressure difference and the WSS proportion at entrance of the H-shaped rupture showed larger hemodynamic parameters than those of the other two types. The risk of dissection rupture for type H was the largest, while type V was in the middle, and type O was the smallest. Conclusions This study provides an effective reference for further numerical analysis the cases and formulation of treatment plans.
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Objective To explore characteristics of flow field around the athletes, change of net flow force, and influences of hip flexion angles at the end of extension kick on the submerged dolphin kick stroke. Methods The body shape data of a swimmer were obtained by three-dimensional (3D) scanning, and the data were reversely reconstructed to obtain the swimmer model. The joints of the swimmer model were separated, and each segment of the athlete was divided into independent rigid body, and simulation of the submerged dolphin kick stroke was realized by controlling movement of each independent rigid body. The computational fluid dynamics (CFD) software package ANSYS Fluent was used as the solver for calculation and solution. Results The vortex structures were shed off from the surface of the swimmer’s body in the area with a large velocity gradient in flow field, and the shedding of vortex structures was different at the stage of extension kick and flexion kick. Propulsion was mainly generated during extension kick phase. At the end of extension kick, the drag decreased as the hip flexion angle increased from 20° to 30°. Conclusions To some extent, increasing flexion angle of the hip joint at the end of extension kick will reduce the drag force and increase the swimming speed in process of the submerged dolphin kick stroke.
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Objective To investigate the effects of athlete’s posture (including bending angle of upper body and angle between body and skis) on aerodynamic characteristics during flight in ski jumping. Methods The athlete and skis were regarded as a multi-body system. By using partially averaged Navier-Stokes (PANS) turbulence model and numerical simulation of computational fluid dynamics (CFD), the aerodynamic characteristics during flight under different postures were predicted. The calculation conditions for bending angle of upper body were 10°, 14°, 18°, 22° and 26°, and the calculation conditions of angle between body and skis were 8°, 12°, 16°, 20° and 24°. Results As the bending angle of upper body increased, the lift force and drag force of the multi-body system, the athlete and skis, and the pitch moment of skis all showed a monotonously decreasing trend, but the ratio of total lift force to total drag force increased first and then decreased. Meanwhile, the pitch moment of the multi-body system decreased first and then increased, and the pitch moment of athlete increased slightly and then decreased. As the angle between body and skis increased, the lift force and drag force of the multi-body system and skis increased first, then decreased and then increased, but the ratio of total lift force to total drag force decreased first, then increased and then decreased. Meanwhile, the lift force, drag force and pitch moment of the athlete increased monotonously, and the pitch moment of the multi-body system and the skis increased first and then decreased. The effect of bending angle of upper body on aerodynamic characteristics during flight in ski jumping was generally significantly larger than that of angle between body and skis. Conclusions The optimal range for bending angle of upper body is 14°-18°, and the optimal range of angle between body and skis is 16°-20°. The influence mechanism for bending angle of upper body and angle between body and skis on aerodynamic characteristics during flight in ski jumping can provide effective auxiliary support for on-the-spot prediction and decisionmaking,
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Objective To investigate the hemodynamic effects of morphological parameters on renal artery stenosis （RAS）, so as to provide theoretical references for clinical practice. Methods The idealized models of RAS were established, then the hemodynamic effects from morphological parameters of stenosis including its area, symmetry, length and shape on renal artery was explored using computational fluid dynamics （CFD） method. Results The renal perfusion, pressure drop and wall shear stress (WSS) distributions in renal artery were significantly correlated with area stenosis (AS). When the stenosis area increased from 50% to 70%, all hemodynamic parameters changed significantly. In addition, an asymmetrical stenosis resulted in a significant increase of abnormally high WSS and length of recirculation flow in renal artery, but the change of stenosis length or shape only led to marginal changes in hemodynamics. Conclusions Although AS is still the most significant factor to influence hemodynamics in RAS, other morphological parameters, especially asymmetric stenosis, cannot be neglected. Therefore, it is suggested that clinical treatment plans should be a comprehensive evaluation based on these morphological parameters.
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Midpalatal corticotomy-assisted rapid maxillary expansion (MCRME) is a minimally invasive treatment of maxillary transverse deficiency (MTD) in young adults. However, the effect of MCRME on respiratory function still needs to be determined. In this study, we evaluated the changes in maxillary morphology and the upper airway following MCRME using computational fluid dynamics (CFD). Twenty patients with MTD (8 males, 12 females; mean age 20.55 years) had cone-beam computed tomography (CBCT) images taken before and after MCRME. The CBCT data were used to construct a three-dimensional (3D) upper airway model. The upper airway flow characteristics were simulated using CFD, and measurements were made based on the CBCT images and CFD. The results showed that the widths of the palatal bone and nasal cavity, and the intermolar width were increased significantly after MCRME. The volume of the nasal cavity and nasopharynx increased significantly, while there were no obvious changes in the volumes of the oropharynx and hypopharynx. CFD simulation of the upper airway showed that the pressure drop and maximum velocity of the upper airway decreased significantly after treatment. Our results suggest that in these young adults with MTD, increasing the maxillary width, upper airway volume, and quantity of airflow by MCRME substantially improved upper airway ventilation.
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Objective To study urodynamic changes of urine at different degrees of hydronephrosis based on computational fluid dynamics (CFD) method, so as evaluate the influence of hydronephrosis degree on kidneys’ ability to discharge stones. Methods Twelve models, including the branched pelvis Model A (normal hydronephrosis A1, mild hydronephrosis A2, medium hydronephrosis A3, severe hydronephrosis A4 models), mature ampullary pelvis Model B (normal hydronephrosis B1, mild hydronephrosis B2, medium hydronephrosis B3, severe hydronephrosis B4 models), and embryo pot abdominal pelvis Model C (normal hydronephrosis C1, mild hydronephrosis C2, medium hydronephrosis C3, severe hydronephrosis C4 models) were established. The urine flow velocity and velocity vector at the neck of the kidney, the outlet of the renal pelvis were calculated by CFD method. Results As the degree of hydronephrosis increased, the flow velocity of urine at the neck of the kidney and the outlet of the renal pelvis decreased. The urinary shearing force of the stones and the kidney’s ability to discharge stones gradually decreased, whereas the circulatory stagnation zone and the velocity boundary layer in kidney aggregate system gradually increased. Conclusions Hydronephrosis can cause changes in urodynamics of the urine. Therefore, the effect of hydronephrosis with different degrees on the patient’s ability to discharge stones after surgery should be fully considered， so as to choose an appropriate treatment method for kidney stones in clinic.
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Objective The flow field of electromagnetically driven pulsating perfusion blood pump was simulated by computational fluid dynamics (CFD) method, and the flow state of blood in blood pump was improved by modifying the structure of pump head, so as to improve its anti-hemolytic performance. Methods The influences of changes in pump head structure on flow field in the pump were analyzed by using Fluent 17.0. Four simulation experiments were carried out to analyze streamline distributions of the internal liquid, the turbulent flow energy distribution on axis of the model, pressure loss of blood flowing through the pump head and shear stress on surface of the model. Results In the four experiments, when the angle between the inlet and outlet of the pump head was symmetrical and the angle between the pump head and the symmetrical axis (α) was 30°, there was no obvious disturbance in the flow line and the turbulence degree was low. In Experiment 1, the pressure loss was 376.8 Pa, with the minimum value. The maximum shear stress in Experiment 2 and 3 was 258.6 Pa and 302.8 Pa, respectively, which met the biomechanical requirements of blood pump such as pressure loss and hemolysis. The model with α=30° was selected as pump head structure of the pulsating blood pump driven by electromagnetic force, and was fabricated by 3D printing technology. Conclusions By optimization of the pump head, the hemolysis performance of the blood pump was improved. The research results can be applied to the design and experiment of a new electromagnetic drive pulse perfusion blood pump.
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Objective To establish a comprehensive method combining physical model experiment and numerical simulation for studying airflow state of upper respiratory tract. Methods Based on CT medical images published online, a three-dimensional (3D) model of human upper respiratory tract was reconstructed. Based on 3D printing technology, an experimental model of the upper respiratory tract was established and the flow process of respiration was measured. A numerical simulation model was created based on the meshing of upper respiratory tract model and the turbulent Realizable k-ε model. Results Firstly, the result of numerical simulation was compared with the experimental conditions, and good agreement was achieved. The numerical simulation results showed that the airflow in respiratory process was in a parabolic shape; the distribution of flow field, pressure on wall and vortex structure were different between inspiratory and expiratory phases; there were air residues in the upper and lower nasal passages during the respiratory exchange process. In addition, the effects of airflow on physiological environment of the upper respiratory tract were preliminarily analyzed through the steak line, pressure field and vortex structure distribution. Conclusions The method proposed in this paper has the characteristics of pertinence, rapidity and accuracy, which gives full play to the advantages of reliable physical experiments and fine numerical simulation, and is applicable for studying different problems of the upper respiratory tract in different cases, with a high value for personalized diagnosis and treatment in clinic.
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Objective Hemodynamic disorder of the pulmonary artery (PA) is the main cause of pulmonary arterial hypertension related to congenital heart disease (PAH-CHD). To study the hemodynamic characteristics of PA, so as to understand biomechanical factors in the occurrence and development of PAH-CHD. Methods Clinical and imaging data were collected in five PAH-CHD patients and five matched controls (Non-PAH) to reconstruct subject-specific three-dimensional (3D) PA models. Computational fluid dynamics (CFD) was performed to compare the hemodynamic difference of flow patterns, wall shear stress (WSS) and normalized energy loss (E·) in the two groups. Results Hemodynamics-related parameters showed that the velocity and WSS were higher in the left and right PA branches of PAH-CHD patients, with significantly lower WSS in the main PA. The E· significantly increased in PAH-CHD patients and positively correlated with normalized PA diameter and inflow. Conclusions Compared with Non-PAH subjects, PAH-CHD patients have obviously higher velocity and WSS in PA branches, lower WSS in main PA and greater E·, indicating these hemodynamic parameters are related with the PAH-CHD, which can be used as potential biomechanical factors for the clinical evaluation of PAH-CHD.
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Objective To investigate the pathogenesis of type-B aortic dissection by using morphological analysis and computational fluid dynamics (CFD) method, so as to provide evidence for the effective prediction of type-B aortic dissection. Methods Six primary type-B dissection cases scanned by CT (dissection group) and six normal cases applied to black-blood MRI (control group) were included in this study and patient-specific three-dimensional (3D) models of aorta were established through image segmentation and 3D reconstruction. The pre-type-B dissection aortas were constructed by applying the scaling algorithm to shrink the dissection and then compared with subjects in control group. The differences between morphological parameters and hemodynamic parameters of the two groups were compared. Results Compared with the normal cases, the area of the descending aorta increased dramatically in dissection group ［(892.03±263.78) mm2 vs (523.67±64.10) mm2, P=0.036］. A significant decrease in angle of the left subclavian artery occurred (66.62°±20.11° vs 100.40°±15.35°, P=0.036). The tortuosity of the aorta also had an obvious increase (0.37°±0.07° vs 0.21°±0.51°, P=0.011). The time-averaged wall shear stress (TAWSS) in dissection group was obviously higher than that in control group; the flow in the dissection region was vortex flow at low speed and the oscillating shear index (OSI) was higher. Conclusions The results of this study can be used to provide guidance for the early diagnosis and treatment of type-B aortic dissection.
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The aerodynamic characteristics of bobsleigh play a very important role in the result of the race. In order to improve the performance, it is necessary to optimize the bobsleigh aerodynamics and reduce its aerodynamic drag as much as possible. Foreign scholars has mainly used computational fluid dynamics (CFD) numerical simulation, wind tunnel experiments and other methods to study the aerodynamic characteristics and optimize drag reduction method, but the relevant research has not yet been carried out in China. In order to have a clear understanding of the technical requirements of bobsleigh aerodynamic optimization and drag reduction, the research result of bobsleigh aerodynamics in recent 20 years have been systematically combed, mainly including numerical simulations and wind tunnel experiments of aerodynamic optimization of bobsleigh body shape and athletes’ positions and attitudes in the bobsleigh, and the possible future development direction of bobsleigh aerodynamics research has been put forward: the systematic study of bobsleigh aerodynamics optimization and comprehensive assessment of bobsleigh aerodynamic drag reduction effects; the study on the interaction between athlete glide control and bobsleigh aerodynamics. These studies will provide an important scientific guidance for the optimization and improvement of bobsleigh sports equipment and the daily training of athletes.
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Objective To comprehensively consider the effect of low diverter (FD) implantation on aneurysmal sac and its branches, so as to provide references for making a more reasonable surgical strategy for intracranial aneurysm embolization in clinical practice. Methods Based on computational fluid dynamics (CFD) method, the FD implantation procedure was simulated by using porous media model innovatively. Changes in hemodynamic parameters of aneurysmal sac and side branch with different diameters before and after FD implantation were compared and analyzed, such as blood flow field, velocity, wall pressure and wall shear stress (WSS). Results FD changed the hemodynamic characteristics of aneurysms. The blood flow velocity decreased significantly. The WSS on aneurysmal neck increased, while the difference of WSS between proximal and distal cervical area reduced conversely. Different side branch diameters of vessels had different effects on hemodynamic characteristic changes. The larger diameter would cause the greater blood flow reduction in side branch after FD implantation, but the decrease in velocity of aneurysmal sac and pressure on aneurysmal roof became smaller simultaneously. Meanwhile, the increase of WSS on aneurysmal neck was inversely proportional to the diameter of side branch. Conclusions The larger branch diameter of vessels would cause the worse effect of FD embolization therapy for intracranial aneurysm, worse atherosclerosis improvements and greater possibilities of branch occlusion or other ischemic complications. Doctors should pay more attention to such cases in FD interventional intravascular embolization in clinic.
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Pulmonary hypertension (PH) is a devastating disease caused by different etiology and characterized by the progressive elevation of pulmonary vascular resistance and pulmonary artery pressure. As a new method that applied to clinical studies, computational fluid dynamics (CFD) gradually becomes a powerful tool for in-depth understanding of the disease progression. It can noninvasively obtain the patient-specific hemodynamic parameters at any point of the vessel and present them through the visualization technology. In this paper, an overall review of CFD with the focus on PH, including the numerical simulation method, boundary conditions, blood characteristics and relevant hemodynamic parameters was presented.
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An explicit illustration of pulmonary delivery processes (PDPs) was a prerequisite for the formulation design and optimization of carrier-based DPIs. However, the current evaluation approaches for DPIs could not provide precise investigation of each PDP separately, or the approaches merely used a simplified and idealized model. In the present study, a novel modular modified Sympatec HELOS (MMSH) was developed to fully investigate the mechanism of each PDP separately in real-time. An inhaler device, artificial throat and pre-separator were separately integrated with a Sympatec HELOS. The dispersion and fluidization, transportation, detachment and deposition processes of pulmonary delivery for model DPIs were explored under different flow rates. Moreover, time-sliced measurements were used to monitor the PDPs in real-time. The Next Generation Impactor (NGI) was applied to determine the aerosolization performance of the model DPIs. The release profiles of the drug particles, drug aggregations and carriers were obtained by MMSH in real-time. Each PDP of the DPIs was analyzed in detail. Moreover, a positive correlation was established between the total release amount of drug particles and the fine particle fraction (FPF) values ( = 0.9898). The innovative MMSH was successfully developed and was capable of illustrating the PDPs and the mechanism of carrier-based DPIs, providing a theoretical basis for the design and optimization of carrier-based DPIs.