研究者詳細 - 玉川　雅章

論文 - 玉川　雅章

分割表示219 件中 21 - 40 件目／全件表示 >>

Evaluation of Virus Concentration Analysis in the Airway by CFD 査読有り国際誌

Yanagita Y., Feng K., Miyamura Y., Basri A.A., Zuber M., Rohani S., Aziz A., Ahmad K.A., Tamagawa M.

Journal of Advanced Research in Numerical Heat Transfer 13 ( 1 ) 96 - 105 2023年06月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Currently, Covid-19 is an epidemic all over the world. When virus directly adhere to mucous membrane of airway by breath, some humans maybe get inflammatory responses by viruses in the first stage of infection. The airway is composed of the nasal cavity, sinuses (Maxillary Sinus, Ethmoid Sinus, Frontal Sinus and Sphenoidal Sinus) and lungs. In the infection stage, the sinuses located in the nasal cavity tend to exhibit particularly high virus concentrations. Therefore, it is important to evaluate quantitatively the areas where viruses are likely to be adhered in the nasal cavity including sinuses. In this study, by CFD including concentration analysis the areas where viruses are likely to be adhered in the nasal cavity are predicted. As for the methods, the nasal cavity was made from 2D-CT image data by Itk-SNAP. For this computation in the nasal cavity continuity equation, Navier-Stokes equation and transport equation are used. And the transport of concentration was computed in the divided 4 parts of nasal cavity. As a result, it was found that the ratio of the concentration to the initial concentration in Ethmoid Sinus is approximately 0.6. It was found that Ethmoid Sinus is the areas where viruses are likely to be adhered and the areas can be predicted by computing the concentration.

DOI： 10.37934/arnht.13.1.96105

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Numerical Simulation to Investigate Interactions of Generated Underwater Micro Shock Waves and Micro Bubbles by Focusing Femtosecond Pulse Laser 査読有り国際誌

Yamamoto A., Toh K., Tamagawa M.

Journal of Advanced Research in Numerical Heat Transfer 13 ( 1 ) 18 - 30 2023年06月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The purpose of this study is to elucidate the mechanism of propagation of the laser-induced micro shock waves under condition where the micro bubbles are generated. In this paper, effects of generated micro bubbles on propagation of the laser-induced micro shock waves were investigated by CFD (computational fluid dynamics). Firstly, the two models (1-D model and 1-D spherical symmetric model) were computed for comparison of the peak pressure variation of the shock waves with propagation. As for governing equations for the propagation of the shock waves, continuity equation, Euler’s momentum equation and Tait’s state equation are used. From the computation, it is confirmed that attenuation of pressure of the 1-D spherical symmetric model was earlier than the 1-D model. In addition, the attenuation of the 1-D spherical symmetric model agreed with the laser-induced shock waves obtained experimentally. However, the peak pressure and duration time of the shock wave was not the same as the experimental result. Then, the bubble behavior was included in the computation of the shock wave propagation. As for the bubble behavior, Rayleigh-Plesset equation is used. From this computation, pressure wave was obtained which superposed the pressure of the shock wave on the internal pressure of the bubble. Although the duration time of the pressure wave was close to the experimental result, the value of the pressure was almost the same as atmospheric pressure. It is suggested that there is a possibility that phenomenon other than the bubbles is generated such as plasma when the shock wave is generated by focusing the femtosecond pulse laser.

DOI： 10.37934/arnht.13.1.1830

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Fundamental Investigation on Ventilation Methods of Indoor Air for Preventing Infections by Computational Fluid Dynamics Analysis 査読有り国際誌

Feng Kaishan, Yanagita Yoshiki, Miyamura Yuko, Basri Adi Azriff, Zuber Mohammad, Rohani Siti, Aziz Abdul, Ahmad Kamarul Arifin, Tamagawa Masaaki

ICIC Express Letters ( ICIC International ) 17 ( 10 ) 1103 - 1110 2023年01月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Droplets including virus such as COVID-19 are easily influenced by the indoor airflow and spreading around everywhere. In general, areas with higher residence time of airflow in the room are more likely to have droplets. Therefore, it is important for predicting the infection risk to use the residence time. In this study, office models with ventilation devices are used and volume-averaged residence time is evaluated as indoor air quality. After making typical office models for the ventilation, indoor air flow motions were predicted by Computational Fluid Dynamics (CFD). By setting the proper boundary conditions for ventilation, effects of ventilation methods for ventilation devices were obtained. It was found that 1) by controlling the operation of devices, ventilation ability can be evaluated by calculating volume-averaged residence time, 2) the value of volume-averaged residence time depends on the degree of angles of device inlets, and 3) volume-averaged residence time for most areas can be decreased by opening a door.

DOI： 10.24507/icicel.17.10.1103

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Evaluation of Hemodynamics Parameters in Carotid Bifurcation System using Numerical Simulation 査読有り国際誌

H. N. Abhilash; S. M. Abdul Khader; Raghuvir Pai; Nitesh Kumar; Mohammad Zuber; John Corda

Applications of Computation in Mechanical Engineering (3rd International Conference on Computing in Mechanical Engineering, ICCME 2021), Lecture Notes in Mechanical Engineering ( Springer ) 149 - 161 2022年11月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Online

Hemodynamics plays a major role in the development of numerous diseases and disorders, including atherosclerosis and stroke. Hemodynamic forces must be adequately mapped to precisely predict and avoid various illnesses and disorders. Blood is a complicated biological fluid that contains constituents, such as erythrocytes that cause it to behave in a non-Newtonian manner. This component is usually overlooked while studying carotid blood flow, and blood is modeled as a Newtonian fluid with constant viscosity. In the present study comparison of hemodynamics in carotid artery for Newtonian viscosity model and non-Newtonian Carreau-Yasuda (CY) viscosity model is done. Computational fluid dynamics analysis is carried out for four patient-specific healthy carotid artery models. The geometry of the carotid artery is obtained from a CT scan and a 3D model is generated using MIMICS. Blood enters the carotid artery through a common carotid artery (CCA) and splits into two arteries named internal carotid artery (ICA) and external carotid artery (ECA). The pulsatile velocity boundary condition is considered at CCA, and the pulsatile pressure boundary condition is considered for both ICA and ECA. The results obtained for both Newtonian and Carreau Yasuda's viscosity models are studied and compared. Wall shear stress is calculated and when compared, results obtained from the Newtonian viscosity model overestimates WSS in certain regions like CCA, ICA, and ECA.

DOI： 10.1007/978-981-19-6032-1_12

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Comparison of Newtonian and Non-Newtonian Flow in Abdominal Aorta and Renal Artery Using Numerical Simulation 査読有り国際誌

Shenoy, B.G.; Kumar, N.; Barbouza, A.B.V.; Khader, S.M.A.; Prabhu, A.R.; Tamagawa, M.; Pai, B.R.

Applications of Computation in Mechanical Engineering, Lecture Notes in Mechanical Engineering ( Springer ) 163 - 172 2022年11月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Online

Numerical simulations of cardiovascular flows have emphasized investigating the mechanics of blood flow in arteries. The objective of the current study is to examine the effect of Newtonian and non-Newtonian flow models in flow simulation to analyze for hemodynamic behavior. CFD analysis was performed on an idealized healthy abdominal aorta with renal branching using ANSYS Fluent solver. The discretized mesh was obtained having polyhedral and hexahedral grid ensured the capture of gradients with a sufficient number of grids. Transient analysis was performed using pulsatile flow boundary conditions. Velocity plots obtained from the analysis predict the recirculation zone in the Ostia of the renal artery. TAWSS observed to be maximum at the infrarenal aorta. And Newtonian model predicted higher TAWSS. Oscillatory shearing index calculated to be maximum at the bifurcation. The result of this analysis will be helping in understanding the flow behavior in idealized cases and further extended to stenosed cases.

DOI： 10.1007/978-981-19-6032-1_13

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Effects of underwater plane shock waves on neutrophil propulsion 査読有り国際誌

Rintaro OBANA, Ayumu YAMAMOTO, Masaaki TAMAGAWA

Journal of Biomechanical Science and Engineering ( Japan Society of Mechanical Engineers ) Advance Publication (早期公開） 2022年06月

Influence of Altered Pressures on Flow Dynamics in Carotid Bifurcation System Using Numerical Methods 査読有り国際誌

Abhilash Hebbandi Ningappa, Suraj Patil, Gowrava Shenoy Belu, Augustine Benjamin Valerian Barboza, Nitesh Kumar, Raghuvir PaiBallambat, Adi Azriff Basri, Shah Mohammed Abdul Khader, Masaaki Tamagawa

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences ( Semarak Ilmu Publishing ) 97 ( 1 ) 47 - 61 2022年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

The application of numerical methods like CFD to understand hemodynamics in arteries has excellent potential to solve complex flow problems. In recent years, CFD has been primarily used in the hemodynamics of the carotid artery due to advances in computational resources. This technique is widely used to obtain knowledge on hemodynamics, predict the risk factors for the development and progression of the atherosclerotic lesion, and analyze local flow profiles due to changes in the carotid artery geometry. This fundamental study will be supportive in observing the blood flow behavior through arteries and studying arterial diseases. The present study investigates three different subject-specific carotid bifurcation models under altered blood pressure conditions. Subject-specific 3D carotid bifurcation modeling is carried out using Materialize software. Unsteady flow simulation is conducted in ANSYS Fluent under the rigid wall and Newtonian conditions. The haemodynamic parameters such as vorticity, helicity, and time-averaged wall shear stress (TAWSS) were evaluated to understand better the beginning and progression of atherosclerotic plaques in the bifurcation. Also, the influence of geometric variation in the bifurcation region was investigated, and it was observed that this region causes significant vortex formation zones. A noticeable reduction in velocity and backflow formation was observed, which reduced the shear stress. It is established that the regions of low TAWSS along the bifurcation region are likely to develop atherosclerosis.

DOI： 10.37934/arfmts.97.1.4761

DOI： 10.37934/arfmts.97.1.4761

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Investigating the Effect of a Single Peristalsis Wave on Unobstructed Ureter Using a Computational Technique 査読有り国際誌

Keni L.G., Satish Shenoy B., Hegde P., Prakashini K., Tamagawa M., Khader S.M.A., Hameed B.M.Z., Zuber M.

Engineered Science 20 330 - 340 2022年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

The ureter transports urine from the kidney to the bladder. During the peristalsis, the contraction of the ureter helps to move the urine in bolus form. In the current work, the ureter is modeled and a single peristalsis wave is used to know the effect of pressure and velocity at a different location in the ureter at different intervals of time for four inlet boundary conditions. A three-dimensional ureter model with 275 mm length is used in the current work. The analysis is carried out using a commercially available computational dynamic package ANSYS-CFX. A single sinusoidal peristaltic wave with a change in pressure is used for the analysis. The inlet pressure is varied as 0.1 Pa, 0.3 Pa, 0.5 Pa, and 0.7 Pa. The maximum pressure was found to be 1.28 Pa at an input pressure of 0.7Pa. In the neck region, a negative pressure of -1.03 Pa is observed at 0.1 Pa. At time T/4, it is observed that the maximum velocity of 0.0406 m/s at N1. In all the other time steps and locations, the minimum velocity of 0.017 m/s is observed. The reverse flow due to negative pressure will develop the urinary tract infection in the ureter and result in the bacteria and toxins from the ureter into the renal pelvis and kidneys.

DOI： 10.30919/es8d734

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PREDICTION OF THROMBUS FORMATION ON IMPINGING JET FLOW BY EULERIAN COMPUTATIONAL FLUID DYNAMICS (CFD) –EFFECTS OF CONCENTRATION BOUNDARY CONDITIONS ON PLATELET ADHESION– 査読有り国際誌

Yamaguchi T., Basri A.A., Ahmad K.A.B., Tamagawa M.

International Journal of Innovative Computing, Information and Control ( ICIC International 学会 ) 18 ( 2 ) 657 - 666 2022年04月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

For the thrombus formation in medical fluidics, it is considered that stagnation of the flow, shear rate and adhesion on the wall are important physical factors. Affeld et al. suggested that shear rate distribution and particle adhesion distribution on the wall are important factors by their experiment of impinging jet flow with stagnation point, and also showed that adhesion mechanism of platelets on the flow field is also important by theoretical evaluation. However, the effect of platelet adhesion on white thrombus formation by shear flow is still now unknown. In this paper, to improve accuracy of the prediction for platelet adhesion, transport process of concentration on impinging jet flow based on Affeld et al.’s experiment is analyzed by finite difference CFD with modifying the thrombus evaluation model. In addition, distribution of concertation on the wall is tried to be evaluated by setting simple boundary conditions of concertation for platelets adhesion. It is concluded that the distribution of platelet adhesion on the wall surface can be predicted accurately by the proposed evaluation method composed of distribution of concentration, velocity and shear rate with adjusting the threshold.

DOI： 10.24507/ijicic.18.02.657

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Prediction of Thrombus Formation on Impinging Jet Flow by Eulerian Computational Fluid Dynamics (CFD) -Effects of Concentration Boundary Conditions on Platelet Adhesion- 査読有り国際誌

Taishin Yamaguchi, Adi Azriff Basri, Kamarul Arifin Bin Ahmad, Masaaki Tamagawa

International Journal of Innovative Computing, Information and Control (IJICIC) ( ICIC International ) 18 ( 2 ) 657 - 666 2022年02月

Ureterdynamic Analysis of Multiple Peristaltic Waves on Variable Diameter Ureter 査読有り国際誌

Laxmikant G Keni, Mattias Jan Hayoz, Satish Shenoy B, Padmaraj Hegde, Prakashini K, Masaaki Tamagawa, Shah Mohammad Abdul Khader and Mohammad Zuber

Engineered Science 17 256 - 265 2022年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

In ureter physiology, the peristaltic mechanism is involved in urine transport from the kidney to the bladder through the ureter. The constrictions in the ureter develop the critical regions for ureter disease. ANSYS-CFX is used to analyze the flow dynamics. Multiple peristalsis waves are made to propagate over the tapered ureter model to understand the formation of bolus and reflux effect. The effect of the peristaltic sinusoidal wave propagating along the tapered circular tube results in pressure, velocity, pressure gradient, and wall shear distribution inside the ureter. The maximum pressure is created by the urine bolus of the single wave as it flows in front of the ascending urine bolus. This creates a negative pressure gradient, which can lead to a reverse flow. The high wall shear stress may affect the function of the kidney and play an important role in various kidney diseases. In triple wave due to incomplete wave propagation at the end, the minimum pressure gradient is recorded at the neck region due to contraction in the area. Also, the velocity shows a reverse flow at the outlet and this may lead to some urinary infection in the ureter.

DOI： 10.30919/es8e615

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Simulation of Mechanical Heart Valve Dysfunction and the Non-Newtonian Blood Model Approach 査読有り国際誌

Chen A., Basri A.A.B., Ismail N.B., Tamagawa M., Zhu D., Ahmad K.A.

Applied Bionics and Biomechanics 2022 2022年01月

記述言語：英語掲載種別：記事・総説・解説・論説等（学術雑誌）

The mechanical heart valve (MHV) is commonly used for the treatment of cardiovascular diseases. Nonphysiological hemodynamic in the MHV may cause hemolysis, platelet activation, and an increased risk of thromboembolism. Thromboembolism may cause severe complications and valve dysfunction. This paper thoroughly reviewed the simulation of physical quantities (velocity distribution, vortex formation, and shear stress) in healthy and dysfunctional MHV and reviewed the non-Newtonian blood flow characteristics in MHV. In the MHV numerical study, the dysfunction will affect the simulation results, increase the pressure gradient and shear stress, and change the blood flow patterns, increasing the risks of hemolysis and platelet activation. The blood flow passes downstream and has obvious recirculation and stagnation region with the increased dysfunction severity. Due to the complex structure of the MHV, the non-Newtonian shear-thinning viscosity blood characteristics become apparent in MHV simulations. The comparative study between Newtonian and non-Newtonian always shows the difference. The shear-thinning blood viscosity model is the basics to build the blood, also the blood exhibiting viscoelastic properties. More details are needed to establish a complete and more realistic simulation.

DOI： 10.1155/2022/9612296

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Numerical Analysis on A Non-Critical Stenosis in Renal Artery 査読有り

Hegde P., Gowrava S.B., Barboza A.B.V., Khader S.M.A., Pai R., Tamagawa M., Prabhu R., Rao D.S.

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 88 ( 3 ) 31 - 48 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

The increase in cardiovascular diseases worldwide has resulted in higher death rate of people globally; the primary reason being atherosclerosis. A better understanding of this condition can be achieved through the application of numerical methods to understand the haemodynamics. The present study aims to investigate the effects of renal artery angulation on the flow characteristics in a non-critically stenosed artery compared to that of a normal artery in order to understand better, the reasons for causes and progression of renal artery stenosis. Abdominal aorta-renal artery models ranging from 30° to 90° angulations were generated from computerized tomography-angiogram slices, post which they were subjected to cleanup and defeaturing. Haemodynamic parameters such as velocity, pressure and time-averaged wall shear stress were evaluated at early systole, peak systole and peak diastole for the different artery models. Extensive amounts of flow recirculation were observed in normal renal arteries with higher bifurcating angles, whereas it was not the case in stenosed arteries where flow acceleration was seen for the duration of the cardiac cycle. Evaluation of static pressure encountered a similar trend where an increase in angulation saw a decrease in pressure for normal arteries which contradicted with stenosed artery results. Analysis of shear stress saw very similar trends in normal and stenosed arteries, with lower angulation profiles experiencing higher values of shear stress at the Ostia. In the cases of arteries of higher angulation with a non-critical stenosis, the possibility of worsening of stenosis into an opprobrious stage remains a concern.

DOI： 10.37934/arfmts.88.3.3148

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CFD Analysis on Effect of Angulation in A Healthy Abdominal Aorta-Renal Artery Junction 査読有り

Hegde P., Shenoy B.G., Khader S.M.A., Pai B.R., Rao D.S., Tamagawa M., Prabhu R., Kumar N., Ahmad K.A.

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 88 ( 1 ) 149 - 165 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

The recent developments in computational fluid dynamics (CFD) can be useful in observing the detailed haemodynamics in renal artery bifurcation for clinical evaluation and treatment. The present study focuses on haemodynamic behaviour of blood as it flows through the abdominal aorta-renal artery junction in an idealistic healthy artery with varying bifurcation angles to the abdominal aorta, i.e. from 30° to 90° with increments of 15°. This is to examine the effect of angulation on the junction and to determine whether arterial geometry plays a role in the prediction of atherosclerotic lesions. The three-dimensional models used in this study were generated using ANSYS WORKBENCH 19.0, and numerical simulation was done using FLUENT 19.0 solver. The blood flow is assumed to be Newtonian, incompressible and laminar. Haemodynamic parameters such as velocity, wall pressure and wall shear stress along with flow variation are compared among the different models. As the angulation increased, velocity and wall shear stress at the ostial region decreased by 14% and 52% respectively. Wall pressure at the same region saw an increase by 3%. Therefore, renal arteries with higher bifurcating angles to the abdominal aorta were observed to be more prone to the formation of atherosclerotic lesions. The present study is a precursor for future studies on renal artery with stenosis

DOI： 10.37934/arfmts.88.1.149165

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Effect of falling down postures on human injuries by multi-body dynamic simulation using opensim 査読有り国際誌

Jiang X., Tamagawa M.

ICIC Express Letters, Part B: Applications ( ICIC International 学会 ) 12 ( 12 ) 1121 - 1128 2021年12月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

As most previous studies on human falling down have been executed by experimental dummy tests, expensive instruments and complex configurations of the research environments are required. To decrease the cost of these experimental tests, it is necessary to develop prediction method for the body injuries caused by falling down through computer simulation. The purpose of this study is to investigate the effect of falling down postures on human injuries by computer simulation. To analyze falling down, the biomechanical analysis software OpenSim was used to rebuild a human model by Gait2354 (bone and muscle) model. Since body tissue cannot be included in dynamic simulation in OpenSim, contact points were added into appropriate part of the body model to imitate the effect of cushion of body structure. The kinematic characteristics of head during falling backward and forward were finally obtained by OpenSim and head injuries were evaluated by the acceleration on center of head. It was concluded that the head injury characteristics of different falling postures can be evaluated by comparing the kinematic results of different falling.

DOI： 10.24507/icicelb.12.12.1121

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Computational flow analysis of a single peristaltic wave propagation in the ureter 査読有り

Keni L.G., Hayoz M.J., Khader S.M.A., Hegde P., Prakashini K., Tamagawa M., Satish Shenoy B., Hameed B.M.Z., Zuber M.

Computer Methods and Programs in Biomedicine 210 2021年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Background and objective: The bladder receives the urine from the kidney and ureter. The series of peristaltic waves facilitate urine transport to the bladder. The peristaltic flow in the ureter is associated with fluid trapping and material reflux, which may cause an increase in bladder pressure. It is difficult to visualize the complex peristalsis phenomenon, in the ureter using image and radiography experiments. A numerical simulation will help in the understanding of urine bolus formation and its effect on the ureter wall. Methods: A three-dimensional computational fluid dynamic analysis is carried out to understand the flow physics associated with bolus formation and the effect of reflux on the ureter. ANSYS-CFX, a commercially available computational dynamics package is used to simulate the peristalsis. A single sinusoidal peristaltic wave traveling along a circular tube will yield the velocity, pressure, wall shear stress distributions inside the ureter. Results: The propagation of the peristaltic wave results in the backflow of urine near the inlet at the beginning of the flow. As the wave propagates towards the outlet, the flow rate decreases. It is observed that pressure distribution along the ureter axis will deteriorate towards the outlet. The contraction produces a very high-pressure gradient which causes the urine backflow. The trapping and the bolus formation cause a significant rise in bolus pressure, simultaneously developing negative pressure at the contraction neck. Conclusions: The effect of peristalsis on the ureter biofluid dynamic behavior of the ureter is visualized in this study. It is established that the peristaltic contraction results in high-pressure formation at the bolus and negative pressure at the neck. It was found to be a maximum of 1.1 Pa at the bolus center and —1.13 Pa at the neck region. At the ureter pelvis junction, a higher wall shear of 0.095 Pa is observed as the wave starts to propagate. The velocity vectors show that the trapping of urine causes reflux and results in an adverse pressure gradient near the wall. A maximum pressure gradient of 485 Pa/meter was observed at the contraction of the ureter wall.

DOI： 10.1016/j.cmpb.2021.106378

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Quantitative haemodynamic study in renal artery bifurcation using CFD 査読有り

Hegde P., Kanjalkar S., Khader S.M.A., Shenoy B.G., Pai B.R., Tamagawa M., Prabhu R., Rao D.S.

Journal of Engineering Science and Technology 16 ( 5 ) 4079 - 4099 2021年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Computational Fluid Dynamics facilitates in the quantitative analysis of haemodynamic processes of in vivo cardiovascular systems. The objective of the present study is to examine the effects of different branching angles of diseased renal arteries with respect to the abdominal aorta on its flow characteristics. Secondly, simulation of normal renal arteries at similar branching angles were also done as a baseline for comparison to comprehend if geometry played a role in the endothelial proliferation in renal artery stenosis. Idealistic renal artery models generated from the digital image of computerized tomography scan were used, with bifurcation angles at the junction ranging from 30° to 90° at successive intervals of 15°. Virtual stenosis of a degree below and above 80% by diameter were generated on the right and left renal artery respectively. The models were discretized using a hybrid polyhedral mesh. Parameters such as time-averaged velocity, time-averaged wall shear stress, pressure difference and fractional flow reserve were used to analyse the flow characteristics. Stenosed renal arteries with higher angulation was found to have larger flow recirculation zones, higher pressure gradient near the Ostia and was observed to experience greater amounts of shear stress at the region of stenosis. For the same degree of stenosis (above 80%), the blockage tended to increase from 18% to 25%, as the angle increased. The effect of angulation was observed to alter the flow characteristics significantly in the stenosed arteries. Critically stenosed (above 80%) renal arteries at a bifurcation angle above 45° showed signs of ischemia.

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Fluid-Structure Interaction in Problems of Patient Specific Transcatheter Aortic Valve Implantation with and Without Paravalvular Leakage Complication 査読有り国際誌

Basri A.A., Zuber M., Basri E.I., Zakaria M.S., Aziz A.F.A., Tamagawa M., Ahmad K.A.

Fluid Dynamics and Materials Processing 17 ( 3 ) 531 - 553 2021年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Paravalvular Leakage (PVL) has been recognized as one of the most dangerous complications in relation to Transcathether Aortic Valve Implantation (TAVI) activities. However, data available in the literature about Fluid Structure Interaction (FSI) for this specific problem are relatively limited. In the present study, the fluid and structure responses of the hemodynamics along the patient aorta model and the aortic wall deformation are studied with the aid of numerical simulation taking into account PVL and 100% TAVI valve opening. In particular, the aorta without valve (AWoV) is assumed as the normal condition, whereas an aorta with TAVI 26 mm for 100% Geometrical Orifice Area (GOA) is considered as the patient aorta with PVL complication. A 3D patient-specific aorta model is elaborated using the MIMICS software. Implantation of the identical TAVI valve of Edward SAPIEN XT 26 (Edwards Lifes ciences, Irvine, California) is considered. An undersized 26 mm TAVI valve with 100% valve opening is selected to mimic the presence of PVL at the aortic annulus. The present research indicates that the existence of PVL can increase the blood velocity, pressure drop and WSS in comparison to normal conditions, thereby paving the way to the development of recirculation flow, thrombus formation, aorta wall collapse, aortic rupture and damage of endothelium.

DOI： 10.32604/fdmp.2021.010925

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Enhancement of neutrophil motion by shock waves for developing new cancer immuno-therapy –effects of surrounding liquid temperature and maximum pressure on neutrophil velocities– 査読有り国際誌

Tamagawa M., Tabata Y.

ICIC Express Letters, Part B: Applications ( ICIC International 学会 ) 12 ( 1 ) 67 - 73 2021年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

This paper describes enhancement of neutrophil motion by shock waves for developing new cancer immuno-therapy with changing environmental conditions such as temperature and working pressure related to initial pressure ratio to activate immune-cells. To obtain the chemotaxis performance of neutrophil, the neutrophil velocity is measured by working gradient of cytokine concentration. In this paper, effects of temperature in the surrounding liquid and working pressure related to initial pressure ratio (maximum pressure of shock wave) on the velocities were investigated. After working 5 shock waves on the suspension liquid of neutrophils, the velocity was measured by image processing on the microscopy. It was concluded that the neutrophil velocities in case of low temperature (10 C) were higher than that in case of high temperature (26 C). The other factor such as duration time of these temperature was discussed. It was also concluded that there should be optimized strength of shock wave to obtain the highest velocity by changing the initial pressure with consideration of surrounding temperature, and the highest amplitude of neutrophil velocity was 1.5 times higher than that without shock wave. ◦ ◦

DOI： 10.24507/icicelb.12.01.67

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85098658046&origin=inward

Development of a novel hybrid method combining finite difference method and dissipative particle dynamics to simulate thrombus formation on orifice flow 査読有り国際誌

Yi Y., Tamagawa M.

Computer Methods in Biomechanics and Biomedical Engineering 23 ( 10 ) 611 - 626 2020年04月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group. In our previous works, the transport of activated platelets (APs) on orifice flow has been simulated by finite difference method (FDM). And the distribution of AP concentration on the flow was obtained. However, the effect of platelet aggregation on the distribution of AP concentration can’t be investigated by FDM because FDM can’t simulate platelet aggregation. On the other hand, platelet aggregation has been simulated by dissipative particle dynamics (DPD). In this paper, a hybrid method combining FDM and DPD is proposed to investigate the effect of platelet aggregation on the distribution of AP concentration. And the hybrid method is used to simulate thrombus formation on orifice flow. As for the effect of platelet aggregation, it is found that the distribution of AP concentration in the hybrid method is different from the distribution in FDM at the places of platelet aggregation. It is considered that the difference is induced by platelet aggregation. As for the distribution of thrombus, higher AP concentration and more aggregated APs are found around the reattachment point and in the recirculation area. It is considered that thrombus is mainly distributed at these places in the simulation. And according to our previous experimental results, thrombus is mainly distributed around the reattachment point and in the recirculation area. It is concluded that the effect of platelet aggregation on the distribution of AP concentration can be investigated by the hybrid method, and the computational results agree with our previous experimental results.

DOI： 10.1080/10255842.2020.1755274

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85083717332&origin=inward

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