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Affiliation |
Graduate School of Engineering Science Cooperative Major in Sustainable Engineering |
AKINAGA Takeshi
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Research Interests 【 display / non-display 】
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Bio-Fluids
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Fluid Engineering
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Sustainability
Graduating School 【 display / non-display 】
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1993.04-1997.03
Doshisha University Graduated
Graduate School 【 display / non-display 】
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-2005.03
Doshisha University Graduate School,Division of Engineering Doctor's Degree Program Accomplished credits for doctoral program
Campus Career 【 display / non-display 】
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2022.04-Now
Akita University Graduate School of Engineering Science Cooperative Major in Sustainable Engineering Associate Professor
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2020.04-2022.03
Akita University Graduate School of Engineering Science Department of Systems Design Engineering Mechanical Engineering Course Associate Professor
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2017.07-2020.03
Akita University Graduate School of Engineering Science Department of Systems Design Engineering Creative Engineering Course Associate Professor
Thesis for a degree 【 display / non-display 】
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Stability and transition of flow past bluff bodies
Takeshi Akinaga
2007.03
Single author
Research Achievements 【 display / non-display 】
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Yamashita H.
Micromachines ( Micromachines ) 12 ( 10 ) 2021.10 [Refereed]
Research paper (journal) Domestic Co-author
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On the Problem of Resonant Incompressible Flow in Ventilated Double Glazing
T. Akinaga, T. M. Harvey-Ball, T. Itano, S. C. Generalis, E. C. Aifantis
Lobachevskii Journal of Mathematics ( Lobachevskii Journal of Mathematics ) 42 ( 8 ) 1753 - 1767 2021.08 [Refereed]
Research paper (journal) International Co-author
We employ a homotopy method, rather than conventional stability theory, in order to resolve the degeneracy due to resonance, which exists in fluid motion associated with a channel of infinite extent in ventilated double glazing. The introduction of a symmetry breaking perturbation, in the form of a Poiseuille flow component, alters substantially the resonant bifurcation tree of the original flow. Previously unknown resonant higher order nonlinear solutions, i.e. after the removal of the perturbative Poiseuille flow component, are discovered. A possible extension of the methodology to consider non-Newtonian gradient enhanced incompressible viscous fluids is also briefly discussed.
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Brine utilisation for cooling and salt production in wind-driven seawater greenhouses: Design and modelling
Takeshi Akinaga, Sotos Generalis, Charlie Paton, Opus Igobo, Philip Davies
Desalination 426 135 - 154 2018.01 [Refereed]
Research paper (journal) Domestic Co-author
Brine disposal is a major challenge facing the desalination industry. Discharged brines pollute the oceans and aquifers. Here is it proposed to reduce the volume of brines by means of evaporative coolers in seawater greenhouses, thus enabling the cultivation of high-value crops and production of sea salt. Unlike in typical greenhouses, only natural wind is used for ventilation, without electric fans. We present a model to predict the water evaporation, salt production, internal temperature and humidity according to ambient conditions. Predictions are presented for three case studies: (a) the Horn of Africa (Berbera) where a seawater desalination plant will be coupled to salt production; (b) Iran (Ahwaz) for management of hypersaline water from the Gotvand dam; (c) Gujarat (Ahmedabad) where natural seawater is fed to the cooling process, enhancing salt production in solar salt works. Water evaporation per face area of evaporator pad is predicted in the range 33 to 83 m 3 /m 2 ·yr, and salt production up to 5.8 tonnes/m 2 ·yr. Temperature is lowest close to the evaporator pad, increasing downwind, such that the cooling effect mostly dissipates within 15 m of the cooling pad. Depending on location, peak temperatures reduce by 8-16 °C at the hottest time of year.
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Convection induced by instabilities in the presence of a transverse seepage
Takeshi Akinaga, Tomoaki Itano, Sotos Generali
Chaos, Solitons & Fractals 91 533 - 543 2016.10 [Refereed]
Research paper (journal) Domestic Co-author
The transition of laterally heated flows in a vertical layer and in the presence of a streamwise pressure gradient is examined numerically for the case of different values Prandtl number. The stability analysis of the basic flow for the pure hydrodynamic case (Pr=0) was reported in [1]. We find that in the absence of transverse pumping the previously known critical parameters are recovered [2], while as the strength of the Poiseuille flow component is increased the convective motion is delayed considerably. Following the linear stability analysis for the vertical channel flow our attention is focused on a study of the finite amplitude secondary travelling-wave (TW) solutions that develop from the perturbations of the transverse roll type imposed on the basic flow and temperature profiles. The linear stability of the secondary TWs against three-dimensional perturbations is also examined and it is shown that the bifurcating tertiary flows are phase-locked to the secondary TWs.
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Transition of planar Couette flow at infinite Reynolds numbers
Tomoaki Itano, Takeshi Akinaga, Sotos C. Generalis, Masako Sugihara-Seki
Physical Review Letter 111 184502 - 184502 2013.10 [Refereed]
Research paper (journal) Domestic Co-author
An outline of the state space of planar Couette flow at high Reynolds numbers (Re<10^{5}) is investigated via a variety of efficient numerical techniques. It is verified from nonlinear analysis that the lower branch of the hairpin vortex state (HVS) asymptotically approaches the primary (laminar) state with increasing Re. It is also predicted that the lower branch of the HVS at high Re belongs to the stability boundary that initiates a transition to turbulence, and that one of the unstable manifolds of the lower branch of HVS lies on the boundary. These facts suggest HVS may provide a criterion to estimate a minimum perturbation arising transition to turbulent states at the infinite Re limit.
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Study on a gas-liquid two-phase flow with the phase changes through a plate heat exchanger
Mishima Kotaro, Fontaine Kevin, Yasunaga Takeshi, Akinaga Takeshi
The Proceedings of the Thermal Engineering Conference ( The Japan Society of Mechanical Engineers ) 2021 ( 0 ) 0069 2021