微气泡生长与溃灭对邻近微球影响的数值模拟研究
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摘要
球形微马达的气泡自驱动实验揭示了微尺度气泡与邻近微球存在着强烈的相互作用,并驱动微球快速运动,但受限于条件,实验无法给出二者相互作用的关键力学因素。为研究这一问题,将微气泡的生长与溃灭类比于虚拟壁面的膨胀与收缩,采用有限元分析法模拟研究了这一瞬态流动。结果表明,微气泡生长与溃灭不具备微尺度流动的可逆性,高速溃灭会使得雷诺数Re显著增大,引入的惯性力驱使邻近微马达产生净位移。这一研究给出了利用气泡动力学打破微尺度游动扇贝定理的新力学机制,并对Janus微马达气泡高效驱动的现象进行了合理解释。
Experiment of spherical micromotor propelled by bubbles reveals that there is a strong interaction between micro-scale bubbles and the adjacent microspheres and self-propelled microsphere can moves rapidly. However, due to the limitation of experimental conditions, it lacks the direct observation evidence for their interaction. In order to study this problem, the growth and collapse of micro-bubble are analogized to the expansion and contraction of a virtual wall. The transient flow is simulated using finite element analysis. The results show that the growth and collapse of microbubbles does not induce a reversible flow. Rapid collapse will make Re significantly increased. The introduction of inertial force to drive adjacent micro-motor produces a net displacement. A new mechanism to break the scallop theorem under the micro-scale swimming is proposed in this paper and the phenomenon of the efficient movement of bubble-driven Janus micromotor is explained reasonably.
Experiment of spherical micromotor propelled by bubbles reveals that there is a strong interaction between micro-scale bubbles and the adjacent microspheres and self-propelled microsphere can moves rapidly. However, due to the limitation of experimental conditions, it lacks the direct observation evidence for their interaction. In order to study this problem, the growth and collapse of micro-bubble are analogized to the expansion and contraction of a virtual wall. The transient flow is simulated using finite element analysis. The results show that the growth and collapse of microbubbles does not induce a reversible flow. Rapid collapse will make Re significantly increased. The introduction of inertial force to drive adjacent micro-motor produces a net displacement. A new mechanism to break the scallop theorem under the micro-scale swimming is proposed in this paper and the phenomenon of the efficient movement of bubble-driven Janus micromotor is explained reasonably.
引文
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[2]LAUGA E.Life around the scallop theorem[J].Soft matter,2011,7(7):3060-3065.
[3]李战华.微流控芯片中的流体流动[M].北京:科学出版社,2012.(LI Zhanhua.Fluid flows in microfluidic chip[M].Beijing:Science Press,2012(in Chinese)).
[4]严宗毅.低雷诺数流理论[M].北京:北京大学出版社,2002.(YANZongyi.Theory on low Reynolds number hydrodynamics[M].Beijing:Peking University Press,2002(in Chinese)).
[5]MORAN J L,POSNER J D.Phoretic self-propulsion[J].Annual review of fluid mechanics,2017,49(1):511-540.
[6]WANG W,DUAN W,AHMED S,et al.Small power:autonomous nano and micromotors propelled by self-generated gradients[J].Nano today,2013,8(5):531-554.
[7]SANCHEZ S,SOLER L,KATURI J.Chemically powered micro and nanomotors[J].Angewandte chemie,2015,54(5):1414-1444.
[8]WANG J,GAO W.Nano/microscale motors:biomedical opportunities and challenges[J].Acs nano,2012,6(7):5745-5751.
[9]胡影影,朱克勤,席葆树.固壁空蚀数值研究[J].应用力学学报,2004,21(1):22-25.(HU Yingying,ZHU Keqin,XI Baoshu.Numerical study of caviation erosion on a rigid wall[J].Chinese journal of applied mechanics,2004,21(1):22-25(in Chinese)).
[10]MEI Y,HUANG G,SOLOVEV A A,et al.Inside front cover:versatile approach for integrative and functionalized tubes by strain engineering of nanomembranes on polymers[J].Advanced materials,2008,20(21):4085-4090.
[11]MANJARE M,YANG B,ZHAO Y P.Bubble driven quasioscillatory translational motion of catalytic micromotors[J].Physical review letters,2012,109(12):128305.
[12]张静,郑旭,王雷磊,等.气泡推进型中空Janus微球运动特性的实验研究[J].实验流体力学,2017,31(2):61-66.(ZHANG Jing,ZHENG Xu,WANG Leilei,et al.Experimental study on the characteristic motion of bubble propelled hollow Janus microspheres[J].Journal of experiments in fluid mechanics,2017,31(2):61-66(in Chinese)).
[13]魏梦举,陈力,伍涛,等.微尺度空泡溃灭驱使微球运动的机理研究[J].物理学报,2017,66(16):164-172.(WEI Mengju,CHENLi,WU Tao,et al.Mechanism of the motion of spherical microparticle induced by a collapsed microbubble[J].Acta physica sinica,2017,66(16):164-172(in Chinese)).
[14]DREYFUS R,BAUDRY J,ROPER M L,et al.Microscopic artificial swimmers[J].Nature,2005,437(7060):862-865.
[15]WILLIAMS B J,ANAND S V,RAJAGOPALAN J,et al.Aself-propelled biohybrid swimmer at low Reynolds number[J].Nature communications,2014,5(2):3081.
[16]QIU T,LEE T C,MARK A G,et al.Swimming by reciprocal motion at low Reynolds number[J].Nature communications,2014,5(5):5119.
[17]BRADY J F.Particle motion driven by solute gradients with application to autonomous motion:continuum and colloidal perspectives[J].Journal of fluid mechanics,2011,667(1):216-259.
[18]CóRDOVAFIGUEROA U M,BRADY J F.Osmotic propulsion:the osmotic motor[J].Physical review letters,2008,100(15):158303.
[19]WANG S,WU N.Selecting the swimming mechanisms of colloidal particles:bubble propulsion versus self-diffusiophoresis[J].Langmuir the acs journal of surfaces&colloids,2014,30(12):3477-3486.
[20]EBBENS S,TU M H,HOWSE J R,et al.Size dependence of the propulsion velocity for catalytic Janus-sphere swimmers[J].Physical review E:statistical,nonlinear,and soft matter physics,2012,85(1/2):020401.
[21]周光炯.流体力学(下册)[M].第2版.北京:高等教育出版社,2000.(ZHOU Guangjiong.Fluid mechanics(volume 2)[M].2nd ed.Beijing:Higher Education Press,2000(in Chinese)).
[22]卢义玉,李晓红,康勇,等.脉冲磨料射流中球泡溃灭特性研究及数值分析[J].应用力学学报,2006,23(2):199-202.(LU Yiyu,LI Xiaohong,KANG Yong,et al.Numerical simulation of dynamic characteristics of spherical bubble collapse in pulsed abrasive water jet[J].Chinese journal of applied mechanics,2006,23(2):199-202(in Chinese)).