Tokyo University of Agriculture and Technology

Institute of Global Innovation Research

グローバルイノベーション研究院 公開セミナー
Institute of Global Innovation Research
Open seminar
Friday, July
2019,13:00 -15:00
言語 / 英語 Language/EnglishProgram

12

東京農工大学 小金井キャンパス 講義棟 L0026教室
Lecture Room L0026, Lecture Hall Building
Koganei Campus, TUAT
Dr. Jose M. Gordillo

13:00-14:00 “A theory on the spreading of droplets"

Professor, University of Seville, Spain

Here we provide a self-consistent analy�cal solu�on describing the unsteady ﬂow in theslender thin ﬁlm which is expelled radially outwards when a drop hits a dry solid wall. Thanks
to the fact that the ﬂuxes of mass and momentum entering into the toroidal rim bordering theexpanding liquid sheet are calculated analy�cally, we show here that our theore�cal results
closely follow the measured �me-varying posi�on of the rim with independence of the we�ng
proper�es of the substrate. The par�culariza�on of the equa�ons describing the rim dynamics
at the instant the drop reaches its maximal extension which, in analogy with the case of Savart
sheets, is characterized by a value of the local Weber number equal to one, provides analgebraic equa�on for the maximum spreading radius also in excellent agreement withexperiments. The self-consistent theory presented here, which does not make use of energe�carguments to predict the maximum spreading diameter of impac�ng drops, provides us withthe �me evolu�on of the thickness and of the velocity of the rim bordering the expanding
sheet. This informa�on is crucial in the calcula�on of the diameters and of the veloci�es of thedroplets ejected radially outwards for drop impact veloci�es above the splashing threshold.
We will use the results obtained to the par�cular case the substrate is superhydrophobic andwill show that the theory is able to predict the splash threshold velocity and also the veloci�esand the diameters of the droplets ejected for impact veloci�es above this threshold.

14:00-15:00 "Drop splashing: Aerodynamic considera�ons"

Dr. Guillaume Riboux

Associate Professor, University of Seville, Spain

When a drop of a low viscosity liquid impacts against a smooth solid substrate at a velocity V, aliquid sheet of thickness very small compare to the drop radius is expelled tangen�ally to thesubstrate at high velocity compare to V. If the impact velocity is such that V > V* with V* thecri�cal velocity for splashing, the edge of the expanding liquid sheet li�s oﬀ from the wall as aconsequence of the gas lubrica�on force at the wedge region created between the advancing
liquid front and the substrate. In the present talk, we show that the magnitude of the gas
lubrica�on force is limited by the values of the slip lengths at the gas-liquid interface and at thesolid. We demonstrate that the splashing regime changes depending on the value of the ra�o ofthe slip lengths, a fact explaining the spreading-splashing-spreading-splashing transi�on for a
reduced value of the surrounding gas pressure as the drop impact velocity increases. We also
provide an expression for V* as a func�on of the inclina�on angle of the substrate, the dropradius, the material proper�es of the liquid and the gas and the mean free path of gas molecules.
■共催／Co-Organized by
グローバルイノベーション研究院 ライフサイエンス分野 田川研究チーム
Institute of Global Innovation “Life Science” Tagawa Team
卓越大学院プログラム
Excellent Leader Development for Super Smart Society
by New Industry Creation and Diversity■お問合せ先／Contact

グローバルイノベーション研究院 工学研究院 田川 義之
Institute of Global Innovation Research, Institute of Engineering,
Assoc. Prof. Yoshiyuki Tagawa
Email: tagawayo (ここに@を入れてください) cc.tuat.ac.jp

詳細はホームページをご覧ください
Please refer to our website for more info.

小金井キャンパス
Koganei Campus

講演会場
Venue

東門
East Gate

正門
Main Gate
どなたでも、ご聴講いただけます。
Everyone is welcome to attend.

https://www.tuat-global.jp
https://www.tuat-global.jp/english/