• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.518-523
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• 2003

Airflow in the nasal cavity of Korean adults is investigated experimentally by PIV measurement. Quantitative data for normal and abnormal nasal cavities with adenoid vegetation are obtained. The CBC PIV algorithm with window offset is used for PIV flow analysis. Average and RMS distributions are obtained for inspirational and expirational nasal airflows. Comparisons between western and Korean nasal airflows are appreciated. Due to the difference in geometry of the frontal part of nasal cavity, the flow near nares shows the difference. For the joint research on nasal deceases, PIV measurements of nasal airflow for nasal cavities with 50% and 70% adenoid vegetation are conducted for the first time. Comparisons in nasal airflows for both normal and abnormal cases are also appreciated.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.33 no.12
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• pp.29-39
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• 2017

The building skins are important architectural elements in both functional and aesthetical aspects. This study focuses on developing a responsive facade with autonomous opening and closing behaviors in accordance with environmental conditions and user requirements for natural ventilation for the office building. The pneumatic ETFE panels are applied as the skin materials taking advantage of the efficiency of the inflatable skin of lightness, architectural performance and sustainable material properties. The biomimetic design methodology is taken for its innovative and visionary concept for the facade design. The interpretation of the building facade in analogy to natural organisms delivers functional and aesthetic characters. By exploring the structural movements of the plant pores, the facade control is developed to be autonomous by the parameter values. The facade opening and closing configurations are derived through parametric modeling and visualization programming. Through the application of this study, expected results are to improve user comfort and energy efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1051-1056
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• 2006

The mean and RMS velocity field of the respiratory gas flow in the human airway was studied experimentally by particle image velocimetry (PIV). Some researchers investigated the airflow for the mouth breathing case both experimentally and numerically. But it is very rare to investigate the airflow of nose breathing in a whole airway due to its geometric complexity. We established the procedure to create a transparent rectangular box containing a model of the human airway for PIV measurement by combination of the RP and the curing of clear silicone. We extend this to make a whole airway including nasal cavities, larynx, trachea, and 2 generations of bronchi. The CBC algorithm with window offset (64 $\times$ 64 to 32 $\times$ 32) is used for vector searching in PIV analysis. The phase averaged mean and RMS velocity distributions in Sagittal and coronal planes are obtained for 7 phases in a respiratory period. Some physiologic conjectures are obtained. The main stream went through the backside of larynx and trachea in inspiration and the frontal side in expiration. There exist vortical motions in inspiration, but no prominent one in expiration.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.103-109
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• 2005

Airflow in the nasal cavity of a normal Korean adult is investigated experimentally by tomographic PIV measurement. Knowledge of airflow characteristics in nasal cavities is essential to understand the physiology and pathology aspects of nasal breathing. Several studies have utilized physical models of the healthy nasal cavity to investigate the relationship between nasal anatomy and airflow. All of these researches on nasal airflow are under the condition of constant flow-rate. In this study, nasal cavity flow with the physiological period is investigated by tomographic PIV, for the first time. A pumping system that can produce the periodic flow is created. Thanks to a new method for the model casting by a combination of the rapid prototyping and curing of clear silicone, a transparent rectangular box containing the complex nasal cavity can be made for PIV, The CBC PIV algorithm is used for analysis. Phase-averaged mean and RMS velocity distributions are obtained for inspirational and expiration nasal airflows. The comparison with the constant flow case is appreciated. There exist many flow patterns depending on each phase.

• Journal of Biomedical Engineering Research
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• v.23 no.6
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• pp.437-449
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• 2002

Coronary arteries are subjected to very different flow conditions compared to other arteries in systemic blood circulation. We Performed a computational fluid dynamic research to investigate influence of such flow conditions in coronary arteries on development and progress of atherosclerosis in the same. The results showed big differences in the flow field of the coronary artery compared to the abdominal and femoral arteries. The coronary artery showed higher wall shear stresses due to the small vessel diameter. On the other hand, it showed only one vortex distal to the stenosis throat during a whole pulse cycle. However. several vortices were observed in the abdominal and femoral arteries in both proximal and distal sides of the stenosis throat The wall shear stresses and extent of recirculation area were increased with impedance phase angle increasing toward more negative values. Therefore, cardiac contraction and the negative impedance phase angle as large as -110。 may induce a flow field that accelerates atherosclerosis.

• Journal of computational fluids engineering
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• v.20 no.2
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• pp.88-95
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• 2015

Blood pump analysis process includes both mechanical and bio-mechanical aspects. Since a blood pump is a mechanical device, it has to be mechanically efficient. On the other hand, blood pumps function is sensitively related to the blood recirculation; hence, bio-factors such as hemolysis and thrombosis become important. This paper numerically investigates the mechanical and bio-mechanical performances of the Rotaflow in the extracorporeal membrane oxygenation(ECMO), Ventricular Assist Device(VAD), and full-load conditions. The operational conditions are defined as(400[mmHg], 5[L/min.]), (100[mmHg], 3[L/min.]), and (600[mmHg], 10[L/min.]) for ECMO, VAD, and full-load conditions, respectively. The results are presented and analyzed from the mechanical aspect via performance curves, and from bio-mechanical aspect via focusing on hemolytic characteristics. Regions of top and bottom cavities show recirculation in both ECMO and VAD condtions. In addition, Eulerian-based calculation of modified index of hemolysis(MIH) has been investigated. The results demonstrate that the VAD condition has the least risk of hemolysis among the others, while the full-load condition has the highest risk.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.419-424
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• 2012

In addition to respiration, the nose performs three other major physiological functions-air-conditioning, filtering, and smelling. On the basis of our experience in experimental investigations of nasal airflows in normal and abnormal nasal cavity models, airflows in the normal model and three artificially deformed models, which simulate the results of surgical treatments (inferior turbinectomy), are investigated by PIV and CFD. The left cavities of all three models are normal, and the right cavities are modified as follows: (1) excision of the head of the inferior turbinate, (2) resection of the lower fifth of the inferior turbinate, and (3) resection of almost the entire inferior turbinate. The use of high-resolution CT data and careful surface rendering of three-dimensional computer models with the help of an ENT doctor provide more sophisticated nasal cavity models. Nasal airflows for both normal and deformed cases are also compared.

• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.93-98
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• 2005

The mean and RMS velocity field of the respiratory gas flow in tile human airway was studied experimentally by particle image velocimetry(PIV). Some researchers investigated the airflow for the mouth breathing case both experimentally and numerically. But it is very rare to investigate the airflow of nose breathing in a whole airway due to its geometric complexity. We established the procedure to create a transparent rectangular box containing a model of the human airway for PIV measurement by combination of the RP and the curing of clear silicone. We extend this to make a whole airway including nasal cavities, larynx, trachea, and 2 generations of bronchi. The CBC algorithm with window offset (64*64 to 32*32) is used for vector searching in PIV analysis. The phase averaged mean and RMS velocity distributions in Sagittal and coronal planes are obtained for 7 phases in a respiratory period. Some physiologic conjectures are obtained. The main stream went through the backside of larynx and trachea in inspiration and the frontal side in expiration. There exist vortical motions in inspiration, but no prominent one in expiration.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1687-1692
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• 2004

Airflow in the nasal cavity of a normal Korean adult is investigated experimentally by tomographic PIV measurement. Knowledge of airflow characteristics in nasal cavities is essential to understand the physiology and pathology aspects of nasal breathing. Several studies have utilized physical models of the healthy nasal cavity to investigate the relationship between nasal anatomy and airflow. All of these researches on nasal airflow are under the condition of constant flow-rate. In this study, nasal cavity flow with the physiological period is investigated by tomographic PIV, for the first time. A pumping system that can produce the periodic flow is created. Thanks to a new method for the model casting by a combination of the rapid prototyping and curing of clear silicone, a transparent rectangular box containing the complex nasal cavity can be made for PIV. The CBC PIV algorithm is used for analysis. Phase-averaged mean and RMS velocity distributions are obtained for inspirational and expiration nasal airflows. The comparison with the constant flow case is appreciated. There exist many flow patterns depending on each phase.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.295-300
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• 2004

Coil embolization technique has been used recently to treat cerebral aneurysms. When a giant or a multilobular aneurysm are treated by roils, filling an aneurysm sac completely with coils is difficult and partial blocking of an aneurysm sac is inevitable. Blood flow characteristics, which nay affect the embolization process of an aneurysm sac, are changed by the locations of coils for the Partially blocked aneurysms. Blood flow fields are also influenced by the geometry of a parent vessel. In order to suggest the coil locations effective for aneurysm embolization, the blood flow fields of lateral aneurysm models were analyzed for the different coil locations and parent vessel geometries. Three dimensional pulsatile flow fields are analyzed by numerical methods considering non-Newtonian viscosity characteristics of blood. Flow rate into the aneurysm sac (inflow rate) and wall shear stress, which are suspected as flow dynamic factors influencing aneurysm embolization, are also calculated. Inflow rates were smaller and the low wall shear stress zones were larger in the neck blocked models compared to the dome blocked models. Smaller inflow and larger low wall shear stress zones in the distal neck blocked model imply that the distal neck should be the effective coil locations for aneurysm embolization.