The Experts below are selected from a list of 55731 Experts worldwide ranked by ideXlab platform
Takashi Yamane - One of the best experts on this subject based on the ideXlab platform.
-
A comparative study between Flow Visualization and computational fluid dynamic analysis for the sun medical centrifugal blood pump.
Artificial Organs, 2004Co-Authors: Takashi Yamane, Yusuke Miyamoto, Koki Tajima, Kenji YamazakiAbstract:: Flow Visualization experiments and computational fluid dynamic (CFD) analyses were performed and the results were compared to clarify the detailed fluid dynamic characteristics for the prototype design of a centrifugal pump, namely, an implantable ventricular assist system from Sun Medical, whose hemocompatibility was previously demonstrated in a series of animal experiments. The Flow Visualization was conducted with particle tracking velocimetry, and the CFD analysis was performed with STAR-CD software. The findings were as follows: (1) There were no Flow separations around the curved open impeller. (2) Antithrombogenic design concepts for the inducer and the vane-shaft clearance were effective in producing axial velocity along the shaft surface and generat-ing suitable shear rates against the stationary fluid. (3) Unsteady vortex shedding in the outlet, which adversely affected the fluid dynamic efficiency, was observed clearly by Flow Visualization. Comparison of velocity distribution measured by Flow Visualization and CFD analysis showed reasonably good correlation. Our findings indicate that the impeller is suitable for an implantable artificial heart. The techniques of Flow Visualization and CFD analysis are complementary evaluation tools in research and development efforts.
-
The most profitable use of Flow Visualization in the elimination of thrombus from a monopivot magnetic suspension blood pump.
Artificial Organs, 2004Co-Authors: Takashi Yamane, Masahiro Toyoda, Osamu Maruyama, M. Nishida, Tatsuo Tsutsui, Tomoaki Jikuya, Osamu Shigeta, Yoshiyuki SankaiAbstract:The purpose of this study was to eliminate fluid dynamic causes of thrombus formation for the monopivot magnetic suspension centrifugal pump under development with the aid of Flow Visualization as an indirect measurement tool for animal experiments. The formation of thrombus observed in early animal experiments was successfully overcome by combining the multiple washout holes at the center into a single hole, optimizing the hole diameter, and eliminating the pivot gap. Flow Visualization was used to optimize the washout hole diameter influencing the Flow around the pivot. In animal experiments Flow Visualization showed that the contours of thrombus corresponded to shear rates of 300 s - 1 or 1300-1700 s - 1 . It was found that Flow Visualization is a useful technique to predict locations where low shear thrombi form and to optimize the pump design in the development stage.
-
Geometric optimization for non-thrombogenicity of a centrifugal blood pump through Flow Visualization
Jsme International Journal Series C-Mechanical Systems Machine Elements and Manufacturing, 2002Co-Authors: Masahiro Toyoda, Osamu Maruyama, M. Nishida, Tatsuo Tsutsui, Takashi Yamane, Yoshiyuki SankaiAbstract:A monopivot centrifugal blood pump, whose impeller is supported with a pivot bearing and a passive magnetic bearing, is under development for implantable artificial heart. The hemolysis level is less than that of commercial centrifugal pumps and the pump size is as small as 160 mL in volume. To solve a problem of thrombus caused by fluid dynamics, Flow Visualization experiments and animal experiments have been undertaken. For Flow Visualization a three-fold scale-up model, high-speed video system, and particle tracking velocimetry software were used. To verify non-thrombogenicity one-week animal experiments were conducted with sheep. The initially observed thrombus around the pivot was removed through unifying the separate washout holes to a small centered hole to induce high shear around the pivot. It was found that the thrombus contours corresponded to the shear rate of 300 s(-1) for red thrombus and 1300 - 1700 s(-1) for white thrombus, respectively. Thus Flow Visualization technique was found to be a useful tool to predict thrombus location.
-
Flow Visualization measurement for shear velocity distribution in the impeller casing gap of a centrifugal blood pump
Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing, 1999Co-Authors: Takashi Yamane, M. Nishida, Balazs Asztalos, Helen Clarke, Toshio KobayashiAbstract:A Flow Visualization study of a centrifugal blood pump was conducted to find the shear and velocity profiles in the back gap between the impeller and the casing. For a wide range of Reynolds numbers and specific speeds, it was found that high shear exists only in the boundary layers of the moving and stationary walls. The velocity profile was essentially laminar. It was also found that the total thickness of the high shear regions is 0.3-0.6mm for conditions of artificial heart and the thickness is determined only by Reynolds number. Hence, it can be concluded that reducing the impeller velocity is the only way to reduce wall shear stress and that increasing the gap width is not effective.
-
Flow Visualization study to improve hemocompatibility of a centrifugal blood pump
Artificial Organs, 1999Co-Authors: M. Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki KonishiAbstract:A correlation study was conducted among quantitative Flow Visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the Flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing gap widths on the Flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small radial gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth Flow and low shear. The small radial gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small radial gap itself is important. It was also confirmed by detailed Flow Visualization and simple laminar shear analysis near the wall that the small radial gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small radial gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow Visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.
Balazs Asztalos - One of the best experts on this subject based on the ideXlab platform.
-
Flow Visualization measurement for shear velocity distribution in the impeller casing gap of a centrifugal blood pump
Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing, 1999Co-Authors: Takashi Yamane, M. Nishida, Balazs Asztalos, Helen Clarke, Toshio KobayashiAbstract:A Flow Visualization study of a centrifugal blood pump was conducted to find the shear and velocity profiles in the back gap between the impeller and the casing. For a wide range of Reynolds numbers and specific speeds, it was found that high shear exists only in the boundary layers of the moving and stationary walls. The velocity profile was essentially laminar. It was also found that the total thickness of the high shear regions is 0.3-0.6mm for conditions of artificial heart and the thickness is determined only by Reynolds number. Hence, it can be concluded that reducing the impeller velocity is the only way to reduce wall shear stress and that increasing the gap width is not effective.
-
Flow Visualization study to improve hemocompatibility of a centrifugal blood pump
Artificial Organs, 1999Co-Authors: M. Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki KonishiAbstract:A correlation study was conducted among quantitative Flow Visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the Flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing gap widths on the Flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small radial gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth Flow and low shear. The small radial gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small radial gap itself is important. It was also confirmed by detailed Flow Visualization and simple laminar shear analysis near the wall that the small radial gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small radial gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow Visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.
-
Flow Visualization measurement of velocity profiles in the impeller housing gap of a centrifugal blood pump
Journal of Life Support Engineering, 1998Co-Authors: Takashi Yaman, M. Nishida, Balazs Asztalos, Helen Clark, Toshio KobayashiAbstract:A Flow Visualization study of a centrifugal blood pump was conducted to find velocity profiles in the gap between the impeller and the housing. Investigating a wide range of Reynolds numbers and specific speeds, it was found that high shear is found only in the boundary layers of the moving and stationary walls and that the total thickness of the boundary layers is 0. 3-0. 6mm depending the Reynolds number.
-
Flow Visualization as a complementary tool to hemolysis testing in the development of centrifugal blood pumps
Artificial Organs, 1998Co-Authors: Takashi Yamane, Toru Masuzawa, M. Nishida, Yoshiyuki Taenaka, Balazs Asztalos, Yuki Miyazoe, Yoshiaki Konishi, Koki Takiura, Kazuyuki ItoAbstract:With a 250% scaled-up pump model, high speed video camera, and argon ion laser light sheet, Flow patterns related to hemolysis were visualized and analyzed with 4 frame particle tracking software. Different Flow patterns and shear distributions were clarified by Flow Visualization for pumps modified to have different hemolysis levels. A combination of in vitro hemolysis tests, Flow Visualization, and CFD analysis suggested a close relationship between hemolysis and high shear caused by small impeller/casing gaps. Because arbitrary cross sections can be illuminated by laser light sheet, Flow Visualization is a useful tool in finding locations related to hemolysis in the design process of rotary blood pumps.
-
development of design methods of a centrifugal blood pump with in vitro tests Flow Visualization and computational fluid dynamics results inhemolysis tests
Artificial Organs, 1998Co-Authors: Koki Takiura, Toru Masuzawa, M. Nishida, Yoshiyuki Taenaka, Takashi Yamane, Seiko Endo, Yoshinari Wakisaka, Eisuke Tatsumi, H Takano, Balazs AsztalosAbstract:There are few established engineering guidelines aimed at reducing hemolysis for the design of centrifugal blood pumps. In this study, a fluid dynamic approach was applied to investigate hemolysis in centrifugal pumps. Three different strategies were integrated to examine the relationship between hemolysis and Flow patterns. Hemolytic performances were evaluated in in vitro tests and compared with the Flow patterns analyzed by Flow Visualization and computational fluid dynamic (CFD). Then our group tried to establish engineering guidelines to reduce hemolysis in the development of centrifugal blood pumps. The commercially available Nikkiso centrifugal blood pump (HPM-15) was used as a standard, and the dimensions of 2 types of gaps between the impeller and the casing, the axial and the radial gap, were varied. Four impellers with different vane outlet angles were also prepared and tested. Representative results of the hemolysis tests were as follows: The axial gaps of 0.5, 1.0, and 1.5 mm resulted in normalized index of hemolysis (NIH) values of 0.0028, 0.0013 and 0.0008 g/100 L, respectively. The radial gaps of 0.5 and 1.5 mm resulted in NIH values of 0.0012 and 0.0008 g/100 L, respectively. The backward type vane and the standard one resulted in NIH values of 0.0013 and 0.0002 g/100 L, respectively. These results revealed that small gaps led to more hemolysis and that the backward type vane caused more hemolysis. Therefore, the design parameters of centrifugal blood pumps could affect their hemolytic performances. In Flow Visualization tests, vortices around the impeller outer tip and tongue region were observed, and their patterns varied with the dimensions of the gaps. CFD analysis also predicted high shear stress consistent with the results of the hemolysis tests. Further investigation of the regional Flow patterns is needed to discuss the cause of the hemolysis in centrifugal blood pumps.
Keisuke Asai - One of the best experts on this subject based on the ideXlab platform.
-
Flow Visualization and transient behavior analysis of luminescent mini tufts after a backward facing step
Flow Measurement and Instrumentation, 2020Co-Authors: Lin Chen, Tomohiro Suzuki, Taku Nonomura, Keisuke AsaiAbstract:Abstract Luminescent mini-tufts method has been used for surface Flow Visualization for a long time. One major challenging point of this method is quantitative analysis of transient Flows and the dynamic structures. This study is focused on the application of luminescent mini-tufts method in transient Flows. A backward-facing step (BFS) is used in this analysis, which is one classic model that consists both Flow separation and re-attachment processes. In this study, the instantaneous mini-tufts recognition, image averaging and tuft inclination angle/tuft angle estimation processes are introduced for the analysis of luminescent mini-tufts for the first time on backward-facing step Flow (Rem = 2.0 × 105–7.9 × 105 and Reh = 1.3 × 104–5.3 × 104). Detailed transient features and characterization process for the backward-facing step model are explained in this study. The combination of optical-oil Flow and hot-wire anemometry methods with luminescent mini-tufts are also shown useful to give comprehensive Flow field information, including the surface Flow behaviors, boundary layer, re-attachment position identification, etc. In addition, the decomposition of the luminescent mini-tufts Visualization data is also conducted to give the power spectral density (PSD) and characteristic frequencies for the mini-tufts behaviors under transient fluctuating Flow conditions.
-
characterization of luminescent mini tufts in quantitative Flow Visualization experiments surface Flow analysis and modelization
Experimental Thermal and Fluid Science, 2019Co-Authors: Lin Chen, Tomohiro Suzuki, Taku Nonomura, Keisuke AsaiAbstract:Abstract As a widely used surface Flow Visualization method, luminescent mini-tuft has become one challenging topic with its practical advantages in quantitative Flow measurement. The luminescent mini-tufts method is preferred with its reduced size and increased luminescence, which is suitable for surface Visualization measurement. To provide a standard method/procedure in quantitative analysis for luminescent mini-tuft measurement, the current study established an experimental characterization platform of luminescent mini-tufts method and conducted flat-pate model for Flow analysis. The experimental system is consisted of wind tunnel and model section, high-speed image data recording system, digital image processing as well as the control system. The digital imaging processing method for result analysis is also explained, which includes the dark current image extraction, averaging, mini-tufts recognition, and tuft inclination angle/tuft angle estimation process. In this study, the steady Flow characterization and quantitative Flow analysis is conducted on a flat plate model (Re = 1.6 × 105–6.6 × 105), which is combined with hot-wire anemometry to investigate the basic surface Flow topology and boundary layer behaviors. The method is shown capable of capturing both the steady and transient behaviors of a surface Flow. Luminescent mini-tufts physical model is also established and found good agreement with the experimental results in this study, which in turn support the mini-tufts characterization and selection in practical applications.
M. Nishida - One of the best experts on this subject based on the ideXlab platform.
-
The most profitable use of Flow Visualization in the elimination of thrombus from a monopivot magnetic suspension blood pump.
Artificial Organs, 2004Co-Authors: Takashi Yamane, Masahiro Toyoda, Osamu Maruyama, M. Nishida, Tatsuo Tsutsui, Tomoaki Jikuya, Osamu Shigeta, Yoshiyuki SankaiAbstract:The purpose of this study was to eliminate fluid dynamic causes of thrombus formation for the monopivot magnetic suspension centrifugal pump under development with the aid of Flow Visualization as an indirect measurement tool for animal experiments. The formation of thrombus observed in early animal experiments was successfully overcome by combining the multiple washout holes at the center into a single hole, optimizing the hole diameter, and eliminating the pivot gap. Flow Visualization was used to optimize the washout hole diameter influencing the Flow around the pivot. In animal experiments Flow Visualization showed that the contours of thrombus corresponded to shear rates of 300 s - 1 or 1300-1700 s - 1 . It was found that Flow Visualization is a useful technique to predict locations where low shear thrombi form and to optimize the pump design in the development stage.
-
Geometric optimization for non-thrombogenicity of a centrifugal blood pump through Flow Visualization
Jsme International Journal Series C-Mechanical Systems Machine Elements and Manufacturing, 2002Co-Authors: Masahiro Toyoda, Osamu Maruyama, M. Nishida, Tatsuo Tsutsui, Takashi Yamane, Yoshiyuki SankaiAbstract:A monopivot centrifugal blood pump, whose impeller is supported with a pivot bearing and a passive magnetic bearing, is under development for implantable artificial heart. The hemolysis level is less than that of commercial centrifugal pumps and the pump size is as small as 160 mL in volume. To solve a problem of thrombus caused by fluid dynamics, Flow Visualization experiments and animal experiments have been undertaken. For Flow Visualization a three-fold scale-up model, high-speed video system, and particle tracking velocimetry software were used. To verify non-thrombogenicity one-week animal experiments were conducted with sheep. The initially observed thrombus around the pivot was removed through unifying the separate washout holes to a small centered hole to induce high shear around the pivot. It was found that the thrombus contours corresponded to the shear rate of 300 s(-1) for red thrombus and 1300 - 1700 s(-1) for white thrombus, respectively. Thus Flow Visualization technique was found to be a useful tool to predict thrombus location.
-
Flow Visualization measurement for shear velocity distribution in the impeller casing gap of a centrifugal blood pump
Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing, 1999Co-Authors: Takashi Yamane, M. Nishida, Balazs Asztalos, Helen Clarke, Toshio KobayashiAbstract:A Flow Visualization study of a centrifugal blood pump was conducted to find the shear and velocity profiles in the back gap between the impeller and the casing. For a wide range of Reynolds numbers and specific speeds, it was found that high shear exists only in the boundary layers of the moving and stationary walls. The velocity profile was essentially laminar. It was also found that the total thickness of the high shear regions is 0.3-0.6mm for conditions of artificial heart and the thickness is determined only by Reynolds number. Hence, it can be concluded that reducing the impeller velocity is the only way to reduce wall shear stress and that increasing the gap width is not effective.
-
Flow Visualization study to improve hemocompatibility of a centrifugal blood pump
Artificial Organs, 1999Co-Authors: M. Nishida, Toru Masuzawa, Yoshiyuki Taenaka, Tomonori Tsukiya, Takashi Yamane, Seiko Endo, Balazs Asztalos, Yuki Miyazoe, Kazuyuki Ito, Yoshiaki KonishiAbstract:A correlation study was conducted among quantitative Flow Visualization analysis, computational fluid dynamic analysis, and hemolysis tests regarding the Flow in a centrifugal blood pump to prevent hemolysis. Particular attention was paid to the effect of the impeller/casing gap widths on the Flow in the volute and in the outlet. Flow vector maps were obtained for 250% scaled-up models with various geometries, using an argon ion laser light sheet, a high speed video camera, and particle tracking velocimetry. In terms of the results, in the small radial gap model, high shear occurred near the inside wall of the outlet and stagnation near the outside wall of the outlet whereas the standard model maintained smooth Flow and low shear. The small radial gap model showed a lower head and greater hemolysis than the standard model. This head decrease could be partly restored by relocating the outlet position; however, the hemolysis level hardly decreased. From these results, it was found that the small radial gap itself is important. It was also confirmed by detailed Flow Visualization and simple laminar shear analysis near the wall that the small radial gap caused a wider high shear layer (110-120 microm) than the standard model (approximately 80 microm). In the small radial gap model, the high shear layer in the outlet (approximately 50 microm) is much narrower than that in the volute. Flow Visualization together with the aid of computational fluid dynamic analysis would be useful to eliminate the causes of hemolysis.
-
Flow Visualization measurement of velocity profiles in the impeller housing gap of a centrifugal blood pump
Journal of Life Support Engineering, 1998Co-Authors: Takashi Yaman, M. Nishida, Balazs Asztalos, Helen Clark, Toshio KobayashiAbstract:A Flow Visualization study of a centrifugal blood pump was conducted to find velocity profiles in the gap between the impeller and the housing. Investigating a wide range of Reynolds numbers and specific speeds, it was found that high shear is found only in the boundary layers of the moving and stationary walls and that the total thickness of the boundary layers is 0. 3-0. 6mm depending the Reynolds number.
Lin Chen - One of the best experts on this subject based on the ideXlab platform.
-
Flow Visualization and transient behavior analysis of luminescent mini tufts after a backward facing step
Flow Measurement and Instrumentation, 2020Co-Authors: Lin Chen, Tomohiro Suzuki, Taku Nonomura, Keisuke AsaiAbstract:Abstract Luminescent mini-tufts method has been used for surface Flow Visualization for a long time. One major challenging point of this method is quantitative analysis of transient Flows and the dynamic structures. This study is focused on the application of luminescent mini-tufts method in transient Flows. A backward-facing step (BFS) is used in this analysis, which is one classic model that consists both Flow separation and re-attachment processes. In this study, the instantaneous mini-tufts recognition, image averaging and tuft inclination angle/tuft angle estimation processes are introduced for the analysis of luminescent mini-tufts for the first time on backward-facing step Flow (Rem = 2.0 × 105–7.9 × 105 and Reh = 1.3 × 104–5.3 × 104). Detailed transient features and characterization process for the backward-facing step model are explained in this study. The combination of optical-oil Flow and hot-wire anemometry methods with luminescent mini-tufts are also shown useful to give comprehensive Flow field information, including the surface Flow behaviors, boundary layer, re-attachment position identification, etc. In addition, the decomposition of the luminescent mini-tufts Visualization data is also conducted to give the power spectral density (PSD) and characteristic frequencies for the mini-tufts behaviors under transient fluctuating Flow conditions.
-
characterization of luminescent mini tufts in quantitative Flow Visualization experiments surface Flow analysis and modelization
Experimental Thermal and Fluid Science, 2019Co-Authors: Lin Chen, Tomohiro Suzuki, Taku Nonomura, Keisuke AsaiAbstract:Abstract As a widely used surface Flow Visualization method, luminescent mini-tuft has become one challenging topic with its practical advantages in quantitative Flow measurement. The luminescent mini-tufts method is preferred with its reduced size and increased luminescence, which is suitable for surface Visualization measurement. To provide a standard method/procedure in quantitative analysis for luminescent mini-tuft measurement, the current study established an experimental characterization platform of luminescent mini-tufts method and conducted flat-pate model for Flow analysis. The experimental system is consisted of wind tunnel and model section, high-speed image data recording system, digital image processing as well as the control system. The digital imaging processing method for result analysis is also explained, which includes the dark current image extraction, averaging, mini-tufts recognition, and tuft inclination angle/tuft angle estimation process. In this study, the steady Flow characterization and quantitative Flow analysis is conducted on a flat plate model (Re = 1.6 × 105–6.6 × 105), which is combined with hot-wire anemometry to investigate the basic surface Flow topology and boundary layer behaviors. The method is shown capable of capturing both the steady and transient behaviors of a surface Flow. Luminescent mini-tufts physical model is also established and found good agreement with the experimental results in this study, which in turn support the mini-tufts characterization and selection in practical applications.