Hiroshi Kawamura
Tokyo University of Science
PhysicsOpen-channel flowTurbulenceHeat transferClassical mechanics
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Publications 180
Abstract Thermocapillary-driven convection in a hanging droplet is experimentally investigated under normal- and micro-gravity conditions. A droplet is hung on a heated cylindrical rod facing downward, and another rod cooled is placed just beneath the droplet to create the designated temperature difference between both ends of the droplet. A transition of the flow field from a two-dimensional axisymmetric ‘steady’ flow to three-dimensional time-dependent ‘oscillatory’ ones by increasing temperat...
2 CitationsSource
#1MasakazutanaseH-Index: 7
view all 24 authors...
#1Koichi Nishino (Yokohama National University)H-Index: 18
#2Taishi Yano (Yokohama National University)H-Index: 8
Last. M. K. ErmakovH-Index: 6
view all 6 authors...
Abstract This paper reports experimental results on the instability of thermocapillary convection in long half-zone liquid bridges of high Prandtl number fluids ( Pr =67, 112 and 207 for 5, 10 and 20 cSt silicone oils, respectively). The experiments were carried out in microgravity on the International Space Station, which allowed sufficiently long waiting period for the development of instability. Critical temperature differences were measured for liquid bridges of 30 and 50 mm diameters and up...
19 CitationsSource
#1Taishi Yano (Yokohama National University)H-Index: 8
#2Koichi Nishino (Yokohama National University)H-Index: 18
Last. Satoshi Matsumoto (JAXA: Japan Aerospace Exploration Agency)H-Index: 9
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This paper reports the experimental results on the instability and associated roll structures (RSs) of Marangoni convection in liquid bridges formed under the microgravity environment on the International Space Station. The geometry of interest is high aspect ratio (AR = height/diameter ≥ 1.0) liquid bridges of high Prandtl number fluids (Pr = 67 and 207) suspended between coaxial disks heated differentially. The unsteady flow field and associated RSs were revealed with the three-dimensional par...
11 CitationsSource
#1Takahiro TsukaharaH-Index: 10
#2Yasuo KawaguchiH-Index: 24
Last. Hiroshi KawamuraH-Index: 18
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Turbulent stripe, which would occur in turbulent channel flows at transitional Reynolds numbers, was studied experimentally by flow visualization using reflective flake particles. In a range of bulk mean Reynolds number Re = 1700-2000, the turbulent stripe was observed to be inclined at angles of 20-30 degree against the streamwise direction, and its streamwise wave length was about 60 times of the channel half width (\delta. The longitudinal streaks with the spanwise spacing of 1.6\deltaw...
9 Citations
Direct numerical simulation of a turbulent channel flow with heat transfer was performed at very low Reynolds numbers. Two different thermal boundary conditions were studied, and temperature was considered as a passive scalar. The computations were carried out with huge computational boxes (up to 327.7 x 2 x 128 in the streamwise, wall-normal, and spanwise directions, respectively). The emphases of this paper are to investigate the large-scale structure (puff) in the intermittent-turbulent flow ...
6 Citations
#1Takahiro TsukaharaH-Index: 10
#2Yohji SekiH-Index: 6
Last. Daisuke TochioH-Index: 5
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Direct numerical simulations (DNS) of fully-developed turbulent channel flows for very low Reynolds numbers have been performed with a larger computational box sizes than those of existing DNS. The friction Reynolds number was decreased down to 60, where the friction Reynolds number is based on the friction velocity and the channel half width. When the Reynolds number was decreased to 60 with small computational box size, the flow became laminar. Using a large box, we found that a localized turb...
28 Citations
3 CitationsSource
#1Takashi Yamane (Kobe University)H-Index: 16
#2Masahiro Nishida (AIST: National Institute of Advanced Industrial Science and Technology)H-Index: 13
Last. Kenji YamazakiH-Index: 3
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The hemocompatibility for the recently approved ventricular assist device EVAHEART® was examined through flow visualization with a 300 % scale-up model. The absence of flow separations around the centrifugal vanes indicated that the curvature of the open vanes was suitable. The flow in the vane-shaft clearance was found to effectively produce sufficient shear stresses along the stationary shaft surface. The hemocompatibility was verified for a wide range of flow conditions.
5 CitationsSource
#1Takashi Yamane (Kobe University)H-Index: 16
#2Ryo Kosaka (AIST: National Institute of Advanced Industrial Science and Technology)H-Index: 9
Last. Tatsuo Tsutsui (University of Tsukuba)H-Index: 11
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The MERA monopivot centrifugal pump has been developed for use in open-heart surgery, circulatory support, and bridge-to-decision for up to 4 weeks. The pump has a closed-type, 50-mm diameter impeller with four straight paths. The impeller is supported by a monopivot bearing and is driven by a radial-flux magnet-coupling motor. Because flow visualization experiments have clarified sufficient pivot wash and stagnation at the sharp corner of the pivot support was suggested, sharp corners were remo...
11 CitationsSource