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Vesicles exposed to shear flow exhibit a remarkably rich dynamics. With the increase of shear rate, one can observe a tumbling-to-tank-treading transition. Besides, a complex oscillating motion, which has alternatively been called trembling, swinging, or vacillating breathing, has also been predicted theoretically and observed experimentally. While in biological systems, vesicles are always decorated by a large number of macromolecules, rendering the dynamics of vesicles in shear flow much more complex. As a powerful supplement to analytical techniques, the dissipative particle dynamics has been proved to be a useful tool in simulating nonequilibrium behaviors under shear. By replacing the conservative force in dissipative particle dynamics with a repulsive Lennard-Jones potential, the density distortion has been overcome and the no-slip boundary condition is achieved. In this article, a nonequilibrium molecular dynamic method is used to study the dynamics of two-dimensional complex vesicles in shear flow. The dynamical behaviors of the complex vesicles are closely related to shear rate and the size of small grafting vesicle. We first consider a vesicle with two small vesicles symmetrically grafted. At a weak flow, the complex vesicle maintains its equilibrium shape and undergoes an unsteady flipping motion, known as tumbling motion. At a moderate shear rate, the tumbling of the vesicle is accompanied with strong shape oscillation, which is consistent with Yazdani's simulation, in which a breathing-with-tumbling type of motion is observed, and is called trembling in this article. As the shear rate further increases, the vesicle is oriented at a fixed angle with respect to the flow direction, while the vesicle membrane circulates around its surface area, exhibiting a well-known tank-treading motion. For sufficiently large grafted vesicles and at a high enough shear rate, a transition from tank-treading to translating motion is observed, in which the flipping of the vesicle or the circulating of the vesicle membrane is hampered. A crossover regime, namely, the tank-treading/translating mixture motion is also found, where translating motion alternates with tank-treading chaotically. However, when a sufficient number of small vesicles are uniformly grafted to the vesicle, the newly observed translating motion is eliminated. This study can give a deeper insight into the complexity of vesicle motions in shear flow.
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Keywords:
- vesicle /
- shear flow /
- nonequilibrium dynamics
[1] Noguchi H, Gompper G 2007 Phys. Rev. Lett. 98 128103
[2] de Haas K, Blom C, van den Ende D, Duits M H G, Mellema J 1997 Phys. Rev. E 56 7132
[3] Kantsler V, Steinberg V 2005 Phys. Rev. Lett. 95 258101
[4] Zabusky N J, Segre E, Deschamps J, Kantsler V, Steinberg V 2011 Phys. Fluids 23 041905
[5] Yazdani A Z K, Bagchi P 2011 Phys. Rev. E 84 026314
[6] Doebereiner H G, Evans E, Krauss M, Seifert U, Wortis M 1997 Phys. Rev. E 55 4458
[7] Guo K, Wang J, Qiu F, Zhang H, Yang Y 2009 Soft Matter 5 1646
[8] Soddemann T, Dünweg B, Kremer K 2003 Phys. Rev. E 68 046702
[9] Finken R, Lamura A, Seifert U, Gompper G 2008 Eur. Phys. J. E 25 309
[10] Deng Z Y, Zhang D, Zhang L X 2015 Materials Today Comm. 3 130
[11] Kaoui B, Biros G, Misbah C 2009 Phys. Rev. Lett. 103 188101
[12] Kaoui B, Ristow G H, Cantat I, Misbah C, Zimmermann W 2008 Phys. Rev. E 77 021903
[13] Kaoui B, Kruger T, Harting J 2013 Soft Matter 9 8057
[14] Wen X H, Zhang D, Zhang L X 2012 Polymer 53 873
[15] Bai Z Q, Guo H X 2013 Polymer 54 2146
[16] Plimpton S J 1995 J. Comput. Phys. 117 1
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[1] Noguchi H, Gompper G 2007 Phys. Rev. Lett. 98 128103
[2] de Haas K, Blom C, van den Ende D, Duits M H G, Mellema J 1997 Phys. Rev. E 56 7132
[3] Kantsler V, Steinberg V 2005 Phys. Rev. Lett. 95 258101
[4] Zabusky N J, Segre E, Deschamps J, Kantsler V, Steinberg V 2011 Phys. Fluids 23 041905
[5] Yazdani A Z K, Bagchi P 2011 Phys. Rev. E 84 026314
[6] Doebereiner H G, Evans E, Krauss M, Seifert U, Wortis M 1997 Phys. Rev. E 55 4458
[7] Guo K, Wang J, Qiu F, Zhang H, Yang Y 2009 Soft Matter 5 1646
[8] Soddemann T, Dünweg B, Kremer K 2003 Phys. Rev. E 68 046702
[9] Finken R, Lamura A, Seifert U, Gompper G 2008 Eur. Phys. J. E 25 309
[10] Deng Z Y, Zhang D, Zhang L X 2015 Materials Today Comm. 3 130
[11] Kaoui B, Biros G, Misbah C 2009 Phys. Rev. Lett. 103 188101
[12] Kaoui B, Ristow G H, Cantat I, Misbah C, Zimmermann W 2008 Phys. Rev. E 77 021903
[13] Kaoui B, Kruger T, Harting J 2013 Soft Matter 9 8057
[14] Wen X H, Zhang D, Zhang L X 2012 Polymer 53 873
[15] Bai Z Q, Guo H X 2013 Polymer 54 2146
[16] Plimpton S J 1995 J. Comput. Phys. 117 1
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