Proceeding of Seventh International Symposium on Turbulence and Shear Flow Phenomena
∗1Department of MechanicalEngineering Keio University Hiyoshi 3-14-1, Kohoku-ku, Yokohama-shi 223... more ∗1Department of MechanicalEngineering Keio University Hiyoshi 3-14-1, Kohoku-ku, Yokohama-shi 223-5866, Kanagawa, Japan email: slowhand@z7.keio.jp (T. Kawata) ... ∗2Laboratoire de Mécanique de Lille Boulevard Paul Langevin 59655 Villeneuve d ′ Ascq Cédex, ...
Introduction: Pipeline flow diversion stent is often placed in a tortuous anatomy. Nevertheless, ... more Introduction: Pipeline flow diversion stent is often placed in a tortuous anatomy. Nevertheless, effect of parent artery curvature on the flow diversion effect from Pipeline stent is poorly understood. The flow diversion effect could be enhanced or diminished depending on the curvature of Pipeline or the angle at which blood flow strikes the Pipeline (angle of incidence). These variations may explain why not all aneurysms are obliterated after Pipeline treatment despite its high efficacy. We evaluated the flow diversion effect of Pipeline in various parent artery curvatures and angle of incidence in in-vitro models. Methods: Four acrylic prototypes of curved tube with a side branch were constructed with circular cross section with the inner diameter of 3.8mm. The variation among the prototypes was made in terms of the radius of curvature R (R=25mm & 50mm), and the relative angle θ of the side branch (θ=60, 90, & 120). The angle θ of the side branch determines the angle of incidence....
Complex flow inside a hard-disk drive (HDD) was investigated using a simplified 3.5” model to cla... more Complex flow inside a hard-disk drive (HDD) was investigated using a simplified 3.5” model to clarify the mechanism causing flow-induced vibration. In contrast to most HDD studies in the past, our model had a non-axisymmetric geometry equipped with a shroud opening and a read/write arm (RWA). The model is designed to serve as a benchmark to study HDD flows both in experiments and in numerical simulations. The complex flow behavior in the disk-to-disk space was investigated with the RWA inserted into the inter-disk space. Flow measurements were carried out with a test rig which consisted of transparent disks, RWA and covers. The measurements were performed at the disk Reynolds number Red=2.4×10 which corresponds to the rotation speed of 7700 rpm of a real 3.5” HDD for desktop computers. Two sets of the flow measurements were performed – the first at different radial locations with the RWA inserted into the space at a shallow angle (experiment I), and the other near the RWA when inser...
Recent developments in marine hydrokinetic (MHK) technology have put the cross-flow (often vertic... more Recent developments in marine hydrokinetic (MHK) technology have put the cross-flow (often vertical-axis) turbines at the forefront. MHK devices offer alternative solutions for clean marine energy generation as a replacement for traditional hydraulic turbines such as the Francis, Kaplan, and Pelton. Following previous power measurements of laboratory-scaled cross-flow hydrokinetic turbines in different configurations, this article presents studies of the water flow field immediately behind the turbines. Two independent turbines, which operated at an average diameter-based Reynolds number of approximately 0.2×105, were driven by a stepper motor at various speeds in a closed circuit water tunnel with a constant freestream velocity of 0.316 m/s. The wakes produced by the three NACA0012 blades of each turbine were recorded with a monoscopic particle image velocimetry technique and analyzed. The flow structures with velocity, vorticity, and kinetic energy fields were correlated with the ...
Following on the 2008-2012 OECD Assessment of Higher Education Learning Outcomes (AHELO) feasibil... more Following on the 2008-2012 OECD Assessment of Higher Education Learning Outcomes (AHELO) feasibility study of civil engineering, in Japan a mechanical engineering learning outcomes assessment working group was established within the National Institute of Education Research (NIER), which became the Tuning National Center for Japan. The purpose of the project is to develop among engineering faculty members, common understandings of engineering learning outcomes, through the collaborative process of test item development, scoring, and sharing of results. By substantiating abstract level learning outcomes into concrete level learning outcomes that are attainable and assessable, and through measuring and comparing the students' achievement of learning outcomes, it is anticipated that faculty members will be able to draw practical implications for educational improvement at the program and course levels. The development of a mechanical engineering test item bank began with test
The Proceedings of Conference of Kanto Branch, 2006
Simuitaneous measurements of fluctuat 至 ng velocity and pressure were carried out in developing r... more Simuitaneous measurements of fluctuat 至 ng velocity and pressure were carried out in developing regiQn of a turbulent mixing layer A min 童 atUre probe fbr f旦 uctuating static pressure was combined with X −wires hot−wire anemometer te evaluate veiocity − pressure correlation at arbitra 理 location ， To capture 血 e contribution Qf largest motion of the flow ， the spatial resQlution ， which is actUally the distance between ye ！ ocity − and pressure − pr。bes， is requlred to be the s e as integral 】 ength scale of the flew ． It is also yalid te check cross − spectrum coherence and phase at the dominant fセequency oflarge scale rnotion ． It ls found that the results which satisfy the criteria coincide well with the DNS result ． Key Urords ： Measurement rnethod ， Non −equilibrium 倉 ee shear layer ， Verocity − pressure correlation ， Cross −spectra
The Proceedings of the Fluids engineering conference, 2006
Fluid structure interactioIl of a circular cyliIlder is silnulated by the coupling of a Vortex El... more Fluid structure interactioIl of a circular cyliIlder is silnulated by the coupling of a Vortex EleInent Method and Bollndary Element Method ， Both methods are volume − mesh − free ， and thus alleviates the bllrdell on handeling m ving bollndary problcms ill gelleral ． The rigid vibration of the cyliIlder is cxamined 丘rst ， and compared wit ． h experlmelltal studics ． Then ， the elast 至 c deformation is considered ．
This study focuses on surveying different turbulence models and dynamic mesh techniques to simula... more This study focuses on surveying different turbulence models and dynamic mesh techniques to simulate a marine hydrokinetic (MHK) crossflow turbine at Rec ≈ 7,000. While several research projects have shown that studies of MHK devices in low Re flow could still yield interesting and significant results, existing computational fluid dynamic (CFD) simulations were conducted at the chord based Re of 105 ∼ 106. The wake and power production of a laboratory-scaled MHK crossflow turbine were numerically simulated and compared with relevant experimental data. The vertical axis turbine operated in a small flume with 20% blockage ratio and was fabricated by mounting three NACA0012 (2.54 cm chord length) straight blades at a radius of 3.41 cm and 15° pitch angle. Within OpenFOAM environment, blade-resolved models were built with Spalart-Allmaras, k-omega shear stress transport (SST), and k-kl-omega unsteady Reynolds-averaged Navier-Stokes simulation (URANS) in both two and three dimensions. Res...
The prediction of turbulent flow separation from smooth surface under adverse pressure gradient i... more The prediction of turbulent flow separation from smooth surface under adverse pressure gradient is one of challenging tasks of engineering turbulence modeling. In the present study, effects of near-wall treatment is examined by comparing different types of turbulence models ...
An open-source 2D Reynolds-averaged Navier–Stokes (RANS) simulation model was presented and appli... more An open-source 2D Reynolds-averaged Navier–Stokes (RANS) simulation model was presented and applied for a laboratory-scaled cross-flow hydrokinetic turbine and a twin turbine system in counter-rotating configurations. The computational fluid dynamics (CFD) model was compared with previously published experimental results and then used to study the turbine power output and relevant flow fields at four blockage ratios. The dynamic stall effect and related leading edge vortex (LEV) structures were observed, discussed, and correlated with the power output. The results provided insights into the blockage effect from a different perspective: The physics behind the production and maintenance of lift on the turbine blade at different blockage ratios. The model was then applied to counter-rotating configurations of the turbines and similar analyses of the torque production and maintenance were conducted. Depending on the direction of movement of the other turbine, the blade of interest could...
Proceeding of Seventh International Symposium on Turbulence and Shear Flow Phenomena
∗1Department of MechanicalEngineering Keio University Hiyoshi 3-14-1, Kohoku-ku, Yokohama-shi 223... more ∗1Department of MechanicalEngineering Keio University Hiyoshi 3-14-1, Kohoku-ku, Yokohama-shi 223-5866, Kanagawa, Japan email: slowhand@z7.keio.jp (T. Kawata) ... ∗2Laboratoire de Mécanique de Lille Boulevard Paul Langevin 59655 Villeneuve d ′ Ascq Cédex, ...
Introduction: Pipeline flow diversion stent is often placed in a tortuous anatomy. Nevertheless, ... more Introduction: Pipeline flow diversion stent is often placed in a tortuous anatomy. Nevertheless, effect of parent artery curvature on the flow diversion effect from Pipeline stent is poorly understood. The flow diversion effect could be enhanced or diminished depending on the curvature of Pipeline or the angle at which blood flow strikes the Pipeline (angle of incidence). These variations may explain why not all aneurysms are obliterated after Pipeline treatment despite its high efficacy. We evaluated the flow diversion effect of Pipeline in various parent artery curvatures and angle of incidence in in-vitro models. Methods: Four acrylic prototypes of curved tube with a side branch were constructed with circular cross section with the inner diameter of 3.8mm. The variation among the prototypes was made in terms of the radius of curvature R (R=25mm & 50mm), and the relative angle θ of the side branch (θ=60, 90, & 120). The angle θ of the side branch determines the angle of incidence....
Complex flow inside a hard-disk drive (HDD) was investigated using a simplified 3.5” model to cla... more Complex flow inside a hard-disk drive (HDD) was investigated using a simplified 3.5” model to clarify the mechanism causing flow-induced vibration. In contrast to most HDD studies in the past, our model had a non-axisymmetric geometry equipped with a shroud opening and a read/write arm (RWA). The model is designed to serve as a benchmark to study HDD flows both in experiments and in numerical simulations. The complex flow behavior in the disk-to-disk space was investigated with the RWA inserted into the inter-disk space. Flow measurements were carried out with a test rig which consisted of transparent disks, RWA and covers. The measurements were performed at the disk Reynolds number Red=2.4×10 which corresponds to the rotation speed of 7700 rpm of a real 3.5” HDD for desktop computers. Two sets of the flow measurements were performed – the first at different radial locations with the RWA inserted into the space at a shallow angle (experiment I), and the other near the RWA when inser...
Recent developments in marine hydrokinetic (MHK) technology have put the cross-flow (often vertic... more Recent developments in marine hydrokinetic (MHK) technology have put the cross-flow (often vertical-axis) turbines at the forefront. MHK devices offer alternative solutions for clean marine energy generation as a replacement for traditional hydraulic turbines such as the Francis, Kaplan, and Pelton. Following previous power measurements of laboratory-scaled cross-flow hydrokinetic turbines in different configurations, this article presents studies of the water flow field immediately behind the turbines. Two independent turbines, which operated at an average diameter-based Reynolds number of approximately 0.2×105, were driven by a stepper motor at various speeds in a closed circuit water tunnel with a constant freestream velocity of 0.316 m/s. The wakes produced by the three NACA0012 blades of each turbine were recorded with a monoscopic particle image velocimetry technique and analyzed. The flow structures with velocity, vorticity, and kinetic energy fields were correlated with the ...
Following on the 2008-2012 OECD Assessment of Higher Education Learning Outcomes (AHELO) feasibil... more Following on the 2008-2012 OECD Assessment of Higher Education Learning Outcomes (AHELO) feasibility study of civil engineering, in Japan a mechanical engineering learning outcomes assessment working group was established within the National Institute of Education Research (NIER), which became the Tuning National Center for Japan. The purpose of the project is to develop among engineering faculty members, common understandings of engineering learning outcomes, through the collaborative process of test item development, scoring, and sharing of results. By substantiating abstract level learning outcomes into concrete level learning outcomes that are attainable and assessable, and through measuring and comparing the students' achievement of learning outcomes, it is anticipated that faculty members will be able to draw practical implications for educational improvement at the program and course levels. The development of a mechanical engineering test item bank began with test
The Proceedings of Conference of Kanto Branch, 2006
Simuitaneous measurements of fluctuat 至 ng velocity and pressure were carried out in developing r... more Simuitaneous measurements of fluctuat 至 ng velocity and pressure were carried out in developing regiQn of a turbulent mixing layer A min 童 atUre probe fbr f旦 uctuating static pressure was combined with X −wires hot−wire anemometer te evaluate veiocity − pressure correlation at arbitra 理 location ， To capture 血 e contribution Qf largest motion of the flow ， the spatial resQlution ， which is actUally the distance between ye ！ ocity − and pressure − pr。bes， is requlred to be the s e as integral 】 ength scale of the flew ． It is also yalid te check cross − spectrum coherence and phase at the dominant fセequency oflarge scale rnotion ． It ls found that the results which satisfy the criteria coincide well with the DNS result ． Key Urords ： Measurement rnethod ， Non −equilibrium 倉 ee shear layer ， Verocity − pressure correlation ， Cross −spectra
The Proceedings of the Fluids engineering conference, 2006
Fluid structure interactioIl of a circular cyliIlder is silnulated by the coupling of a Vortex El... more Fluid structure interactioIl of a circular cyliIlder is silnulated by the coupling of a Vortex EleInent Method and Bollndary Element Method ， Both methods are volume − mesh − free ， and thus alleviates the bllrdell on handeling m ving bollndary problcms ill gelleral ． The rigid vibration of the cyliIlder is cxamined 丘rst ， and compared wit ． h experlmelltal studics ． Then ， the elast 至 c deformation is considered ．
This study focuses on surveying different turbulence models and dynamic mesh techniques to simula... more This study focuses on surveying different turbulence models and dynamic mesh techniques to simulate a marine hydrokinetic (MHK) crossflow turbine at Rec ≈ 7,000. While several research projects have shown that studies of MHK devices in low Re flow could still yield interesting and significant results, existing computational fluid dynamic (CFD) simulations were conducted at the chord based Re of 105 ∼ 106. The wake and power production of a laboratory-scaled MHK crossflow turbine were numerically simulated and compared with relevant experimental data. The vertical axis turbine operated in a small flume with 20% blockage ratio and was fabricated by mounting three NACA0012 (2.54 cm chord length) straight blades at a radius of 3.41 cm and 15° pitch angle. Within OpenFOAM environment, blade-resolved models were built with Spalart-Allmaras, k-omega shear stress transport (SST), and k-kl-omega unsteady Reynolds-averaged Navier-Stokes simulation (URANS) in both two and three dimensions. Res...
The prediction of turbulent flow separation from smooth surface under adverse pressure gradient i... more The prediction of turbulent flow separation from smooth surface under adverse pressure gradient is one of challenging tasks of engineering turbulence modeling. In the present study, effects of near-wall treatment is examined by comparing different types of turbulence models ...
An open-source 2D Reynolds-averaged Navier–Stokes (RANS) simulation model was presented and appli... more An open-source 2D Reynolds-averaged Navier–Stokes (RANS) simulation model was presented and applied for a laboratory-scaled cross-flow hydrokinetic turbine and a twin turbine system in counter-rotating configurations. The computational fluid dynamics (CFD) model was compared with previously published experimental results and then used to study the turbine power output and relevant flow fields at four blockage ratios. The dynamic stall effect and related leading edge vortex (LEV) structures were observed, discussed, and correlated with the power output. The results provided insights into the blockage effect from a different perspective: The physics behind the production and maintenance of lift on the turbine blade at different blockage ratios. The model was then applied to counter-rotating configurations of the turbines and similar analyses of the torque production and maintenance were conducted. Depending on the direction of movement of the other turbine, the blade of interest could...
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