start-ver=1.4 cd-journal=joma no-vol=240 cd-vols= no-issue=3 article-no= start-page=032001 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=2019 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Numerical study of air-entraining and submerged vortices in a pump sump en-subtitle= kn-subtitle= en-abstract= kn-abstract=Numerical detection of harmful vortices in pump sumps, such as an air-entraining vortex (AEV) and a submerged vortex (SMV), is crucially important to develop the drain pump machinery. We performed numerical simulations of the benchmark experiments of the pump sump conducted by Matsui et al. (2006 and 2016) using the OpenFOAM and compared the simulation results with the experimental data considering the effects of turbulence model, grid density and detection method of the vortices. We studied the threshold of the gas-liquid volume fraction of the VOF method and the second invariant of velocity gradient tensor to identify AEV and SMV. The methods proposed in the present paper were found to be very effective for the detection of the vortices, and the simulation results by RANS with the SST k-omega model successfully reproduced the experimental data. LES with the Smagorinsky model, however, was sensitive to the grid system and difficult to reproduce the experimental data even for the finest grid system having 3.7 million cells in the present study. en-copyright= kn-copyright= en-aut-name=YanaseShinichiro en-aut-sei=Yanase en-aut-mei=Shinichiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YamasakiRyo en-aut-sei=Yamasaki en-aut-mei=Ryo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KouchiToshinori en-aut-sei=Kouchi en-aut-mei=Toshinori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=HosodaShunsuke en-aut-sei=Hosoda en-aut-mei=Shunsuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=NagataYasunori en-aut-sei=Nagata en-aut-mei=Yasunori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=ShunjiHiguchi en-aut-sei=Shunji en-aut-mei=Higuchi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=KawabeToshihiko en-aut-sei=Kawabe en-aut-mei=Toshihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=TakamiToshihiro en-aut-sei=Takami en-aut-mei=Toshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= affil-num=1 en-affil=Department of Mechanical and Systems Engineering, Okayama University kn-affil= affil-num=2 en-affil=Technical Division, Tsurumi Manufacturing Co. kn-affil= affil-num=3 en-affil=Department of Mechanical and Systems Engineering, Okayama University kn-affil= affil-num=4 en-affil=Department of Mechanical and Systems Engineering, Okayama University kn-affil= affil-num=5 en-affil=Department of Mechanical and Systems Engineering, Okayama University kn-affil= affil-num=6 en-affil=Technical Division, Tsurumi Manufacturing Co. kn-affil= affil-num=7 en-affil=Technical Division, Tsurumi Manufacturing Co. kn-affil= affil-num=8 en-affil=Department of Mechanical and Systems Engineering, Okayama University of Science kn-affil= END start-ver=1.4 cd-journal=joma no-vol=24 cd-vols= no-issue=1 article-no= start-page=109 end-page=115 dt-received= dt-revised= dt-accepted= dt-pub-year=2012 dt-pub=201201 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Screening of sperm velocity by fluid mechanical characteristics of a cyclo-olefin polymer microfluidic sperm-sorting device en-subtitle= kn-subtitle= en-abstract= kn-abstract=The microfluidic sperm-sorting (MFSS) device is a promising advancement for assisted reproductive technology. Previously, poly(dimethylsiloxiane) and quartz MFSS devices were developed and used for intracytoplasmic sperm injection. However, these disposable devices were not clinically suitable for assisted reproduction, so a cyclo-olefin polymer MFSS (COP-MFSS) device was developed. By micromachining, two microfluidic channels with different heights and widths (chip A: 0.3 x 0.5 mm; chip B: 0.1 x 0.6 mm) were prepared. Sorted sperm concentrations were similar in both microfluidic channels. Linear-velocity distribution using the microfluidic channel of chip B was higher than that of chip A. Using confocal fluorescence microscopy, it was found that the highest number of motile spermatozoa swam across the laminar flow at the bottom of the microfluidic channel. The time required to swim across the laminar flow was longer at the bottom and top of the microfluidic channels than in the middle because of the low fluid velocity. These results experimentally demonstrated that the width of microfluidic channels should be increased in the region of laminar flow from the semen inlet to the outlet for unsorted spermatozoa to selectively recover spermatozoa with high linear velocity. en-copyright= kn-copyright= en-aut-name=MatsuuraKoji en-aut-sei=Matsuura en-aut-mei=Koji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakenamiMami en-aut-sei=Takenami en-aut-mei=Mami kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KurodaYuka en-aut-sei=Kuroda en-aut-mei=Yuka kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=HyakutakeToru en-aut-sei=Hyakutake en-aut-mei=Toru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=YanaseShinichiro en-aut-sei=Yanase en-aut-mei=Shinichiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=NaruseKeiji en-aut-sei=Naruse en-aut-mei=Keiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil= kn-affil=Research Core for Interdisciplinary Sciences, Okayama University affil-num=2 en-affil= kn-affil=Cardiovascular Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University affil-num=3 en-affil= kn-affil=Research Core for Interdisciplinary Sciences, Okayama University affil-num=4 en-affil= kn-affil=Faculty of Engineering, Yokohama National University affil-num=5 en-affil= kn-affil=Graduate School of Natural Science and Technology, Okayama University affil-num=6 en-affil= kn-affil=Cardiovascular Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University en-keyword=laminar flow kn-keyword=laminar flow en-keyword=linear velocity kn-keyword=linear velocity en-keyword=microfluidic sperm sorting kn-keyword=microfluidic sperm sorting en-keyword=motility kn-keyword=motility END start-ver=1.4 cd-journal=joma no-vol=11 cd-vols= no-issue=1 article-no= start-page=25 end-page=33 dt-received= dt-revised= dt-accepted= dt-pub-year=2009 dt-pub=200902 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Application of a numerical simulation to improve the separation efficiency of a sperm sorter en-subtitle= kn-subtitle= en-abstract= kn-abstract=This paper describes a study in which numerical simulations were applied to improve the separation efficiency of a microfluidic-based sperm sorter. Initially, the motion of 31 sperm were modeled as a sinusoidal wave. The modeled sperm were expected to move while vibrating in the fluid within the microchannel. In this analysis, the number of sperm extracted at the outlet channel and the rate of movement of the highly motile sperm were obtained for a wide range of flow velocities within the microchannel. By varying the channel height, and the width and the position of the sperm-inlet channel, we confirmed that the separation efficiency was highly dependent on the fluid velocity within the channel. These results will be valuable for improving the device configuration, and might help to realize further improvements in efficiency in the future. en-copyright= kn-copyright= en-aut-name=HyakutakeToru en-aut-sei=Hyakutake en-aut-mei=Toru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=HashimotoYuki en-aut-sei=Hashimoto en-aut-mei=Yuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=YanaseShinichiro en-aut-sei=Yanase en-aut-mei=Shinichiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MatsuuraKoji en-aut-sei=Matsuura en-aut-mei=Koji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=NaruseKeiji en-aut-sei=Naruse en-aut-mei=Keiji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil= kn-affil=Graduate School of Natural Science and Technology, Okayama University affil-num=2 en-affil= kn-affil=Graduate School of Natural Science and Technology, Okayama University affil-num=3 en-affil= kn-affil=Graduate School of Natural Science and Technology, Okayama University affil-num=4 en-affil= kn-affil=Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University affil-num=5 en-affil= kn-affil=Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University en-keyword=Human reproduction kn-keyword=Human reproduction en-keyword=Microfluid kn-keyword=Microfluid en-keyword=Numerical simulation kn-keyword=Numerical simulation en-keyword=Separation efficiency kn-keyword=Separation efficiency en-keyword=Sperm sorter kn-keyword=Sperm sorter END start-ver=1.4 cd-journal=joma no-vol=353 cd-vols= no-issue= article-no= start-page=115 end-page=162 dt-received= dt-revised= dt-accepted= dt-pub-year=1997 dt-pub=19970721 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Wrap, tilt and stretch of vorticity lines around a strong thin straight vortex tube in a simple shear flow en-subtitle= kn-subtitle= en-abstract= kn-abstract=

the mechanism of wrap, tilt and stretch of vorticity lines around a strong thin straight vortex tube of circulation Γ starting with a vortex filament in a simple shear flow (U=SX2x^1, S being a shear rate) is investigated analytically. an asymptotic expression for the vorticity field is obtained at a large reynolds number Γ/ν » 1, ν being the kinematic viscosity of fluid, and during the initial time St « 1 of evolution as well as St « (Γ/ν)1/2. the vortex tube, which is inclined from the streamwise (X1) direction both in the vertical (X2) and spanwise (X3) directions, is tilted, stretched and diffused under the action of the uniform shear and viscosity. the simple shear vorticity is on the other hand, wrapped and stretched around the vortex tube by a swirling motion, induced by it to form double spiral vortex layers of high azimuthal vorticity of alternating sign. the magnitude of the azimuthal vorticity increases up to O((Γ/ν)1/3S) at distance r=O((Γ/ν)1/3 (νt)1/2) from the vortex tube. the spirals induce axial flows of the same spiral shape with alternate sign in adjacent spirals which in turn tilt the simple shear vorticity toward the axial direction. as a result, the vorticity lines wind helically around the vortex tube accompanied by conversion of vorticity of the simple shear to the axial direction. the axial vorticity increases in time as s2t, the direction of which is opposite to that of the vortex tube at r=O((Γ/ν)1/2 (νt)1/2) where the vorticity magnitude is strongest. in the near region r « (Γ/ν)1/3 (νt)1/2, on the other hand, a viscous cancellation takes place in tightly wrapped vorticity of alternate sign, which leads to the disappearance of the vorticity normal to the vortex tube. only the axial component of the simple shear vorticity is left there, which is stretched by the simple shear flow itself. as a consequence, the vortex tube inclined toward the direction of the simple shear vorticity (a cyclonic vortex) is intensified, while the one oriented in the opposite direction (an anticyclonic vortex) is weakened. the growth rate of vorticity due to this effect attains a maximum (or minimum) value of ±S2/33/2 when the vortex tube is oriented in the direction of X^1+X^2[minus-or-plus sign] X^3. the present asymptotic solutions are expected to be closely related to the flow structures around intense vortex tubes observed in various kinds of turbulence such as helical winding of vorticity lines around a vortex tube, the dominance of cyclonic vortex tubes, the appearance of opposite-signed vorticity around streamwise vortices and a zig-zag arrangement of streamwise vortices in homogeneous isotropic turbulence, homogeneous shear turbulence and near-wall turbulence.

en-copyright= kn-copyright= en-aut-name=KawaharaGenta en-aut-sei=Kawahara en-aut-mei=Genta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KidaShigeo en-aut-sei=Kida en-aut-mei=Shigeo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TanakaMitsuru en-aut-sei=Tanaka en-aut-mei=Mitsuru kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=YanaseShinichiro en-aut-sei=Yanase en-aut-mei=Shinichiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil= kn-affil=Ehime University affil-num=2 en-affil= kn-affil=National Institute for Fusion Science affil-num=3 en-affil= kn-affil=Kyoto Institute of Technology affil-num=4 en-affil= kn-affil=Okayama University END