研究者業績

高垣 直尚

タカガキ ナオヒサ  (Naohisa Takagaki)

基本情報

所属
兵庫県立大学 工学研究科 機械工学専攻 教授
学位
博士(工学)(2009年3月 京都大学)

連絡先
takagakieng.u-hyogo.ac.jp
研究者番号
00554221
ORCID ID
 https://orcid.org/0000-0002-9672-0920
J-GLOBAL ID
201401024740331854
researchmap会員ID
7000008779

外部リンク

私の研究室では、基礎的な流体力学の知識をもって、従来の機械工学分野の枠に囚われない(地球物理、化学工学、医学など他分野にまたがった)学際的で産学連携も視野に入れた研究に力を入れ取り組んでいます。大学の講義においては、流体力学の応用性の高さを伝えられるように心がけています。


論文

 55
  • 高垣 直尚, 中島 裕一郎, 黒瀬 良一, 小森 悟, 馬場 雄也
    日本機械学会論文集B編 76(772) 2065-2074 2010年12月  
    A three-dimensional direct numerical simulation (DNS) with Level-Set method is applied to the impingement process of a single droplet with diameter of 1.2〜2.2mm on the air-water free surface, and the characteristics of vortices induced below the free surface are investigated by comparing with the experiments. The results show that the present DNS can capture the generation and transportation process of the vortices. The predicted vortex intensity corresponds with the experimental bestfit curve proposed for a larger droplet with diameter of 2.2〜5.6mm. In addition, the comparisons of velocity vectors and scalar concentration fields between the vertical and oblique impingements show that the momentum and mass transfer mechanism are strongly affected by the angle of droplet's impingement.
  • 高垣 直尚, 小森 悟
    日本機械学会論文集B編 74(748) 2459-2465 2008年12月25日  
    The mechanism of mass transfer due to a single droplet impinging on the air-water interface was investigated using PIV and LIF techniques. Velocity and CO2 concentration fields in the liquid side after the impingement of a single droplet were visualized. The radius and the velocity of the surfacerenewal vortex induced by the droplet impingement were estimated. It is found that CO2 near the free surface goes downward due to the surface-renewal vortex induced by the impinging droplet, and both the radius and velocity of the vortex increase with increasing the vertical momentum of the droplet. This suggests that the droplet impinging on the free surface promotes mass transfer across the air-water interface.
  • Naohisa Takagaki, Satoru Komori
    Journal of Geophysical Research: Oceans 112(6) 2007年6月8日  査読有り
    [1] The effects of rainfall on mass transfer across the air-water interface and turbulent structure were investigated through laboratory experiments in a turbulent open-channel flow. The air-water CO2 transfer coefficient due to raindrops impinging on the air-water surface and turbulence quantities in an open-channel flow were measured. The results show that rainfall enhances turbulent mixing near the free surface on the liquid side, and the enhancement results in increase of CO2 transfer across the air-water interface. The mass transfer coefficient on the liquid side is well correlated with the mean vertical momentum flux of rainfall (MF), but it is not well correlated with the mean kinetic energy flux of raindrops impinging on the unit area of the air-water interface (KEF), as has been proposed in previous studies. The maximum value of the mass transfer coefficient obtained in the present rain experiments corresponds to that observed in oceans with high wind speeds. This suggests that it is of great importance to consider the effects of rainfall in precisely estimating the local air-sea CO2 exchange rate.
  • Satoru Komori, Naohisa Takagaki, Rina Saiki, Naoya Suzuki, Kenji Tanno
    TRANSPORT AT THE AIR-SEA INTERFACE: MEASUREMENTS, MODELS AND PARAMETRIZATIONS 169-179 2007年  査読有り
    The effects of impinging raindrops on both turbulence below the air-water interface and CO2 transfer across the air-water interface are discussed using laboratory measurements by Takagaki and Komori [1]. The measurements of CO2 absorption rate and turbulence quantities in an open-channel flow show that impinging raindrops enhance both turbulent mixing near the free surface on the liquid side and CO2 transfer across the air-water interface, and that the mass transfer velocity due to impinging raindrops is well correlated with the mean vertical momentum flux of raindrops. The reason why the mass transfer velocity is well correlated by the mean vertical momentum flux is explained by showing the instantaneous velocity vectors induced by a falling single droplet. Further, in order to clarify the effects of rainfall on the global and local CO2 transfer across the air-sea interface, the mean annual net air-sea CO2 flux was estimated using both the daily precipitation data set and the empirical correlation [1] between the mass transfer velocity and mean vertical momentum flux. The rainfall effects are also compared with wind shear effects. The results show that rainfall effects are significant for the local CO2 budget between atmosphere and ocean in equatorial and mid-latitude regions, but are not so important for global budget, compared to the wind shear effect.
  • 高垣 直尚, 小森 悟
    日本機械学会論文集B編 71(712) 2900-2906 2005年12月25日  
    The effects of rainfall on both mass transfer across the air-water interface and turbulence structure in the interfacial region were investigated through laboratory experiments in a turbulent open-channel flow. The CO2 absorption rate by rain droplets impinging on the free surface and turbulence quantities were measured. The results show that the rainfall enhances the turbulent mixing near the free surface on the liquid side and the CO2 transfer across the air-water interface. The mass transfer coefficient on the liquid side is well correlated by the mean kinetic energy of rain droplets impinging on the unit area of the air-water interface, KEF, and it is proportional to the square root of KEF. The maximum value of the mass transfer coefficient obtained in this study corresponds to that obtained in wind-driven turbulence with wind speed 15 m/s. This suggests that it is of great importance to consider the effects of rainfall on the CO2 exchange rate in a general circulation model for estimating the global warming.

MISC

 19

講演・口頭発表等

 154

担当経験のある科目(授業)

 19

所属学協会

 7

共同研究・競争的資金等の研究課題

 25

産業財産権

 1

社会貢献活動

 9