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Dynamics of defects in domain walls parametrically exited capillary ripples


V.O. Afenchenko, S.V. Kiyashko, A.V. Nazarovsky

In work dynamics of defects in domain walls which can arise on limit of the section of two domains, at parametrical excitement of capillary waves on a liquid surface is experimentally investigated. Such domains are formed because in spatially extended strongly dissipative systems development of instability and formation of structures in various parts of space occurs almost independently. The similar situation is observed and at parametrical excitement of capillary ripples on a surface of liquid of small homogeneous depth and small viscosity. Experiment was carried out as follows. In a cavity the liquid layer in thickness of 0,5–0,8 mm was located. Cavities of a round form of 150 mm were used. and the square party with length of 140 mm. As liquid silicone PMS-5 oil with known parameters was used. A cavity it was fixed on vibro-table TIRA–VIB. The operating sinusoidal signal from the quartz generator moved on the amplifier of vibro-table. After that at the fixed frequency changed amplitude of an external signal, achieving emergence of the square lattice consisting of two pairs mutually orthogonal standing capillary waves. At increase of supercriticality in liquid small, in comparison with length of raised waves, depth, the regular square structure of standing waves is broken and there are topological defects which could form further domain walls. Repeating procedure of change of amplitude of external force repeatedly existence of two domains divided among themselves by a rectilinear, symmetric domain wall, consisting of defects of one sign achieved. Further dynamics of defects in a domain wall in the course of its evolution was experimentally investigated, was at the same time fixed a two-dimensional picture of a field on a video camera. After processing of videos the distance between defects was measured and the density of defects depending on a corner between domains was calculated. Coordinates of defects for the various moments of time were defined and schedules of such dependences for all defects in a domain wall were under construction. The measurements were performed for different supercriticalities and in the cuvettes of different geometry. Found that in the symmetric domain walls defects move strictly along the domain wall. Thus they are accelerated by one and annihilate at the boundary of the cell, and the density of defects decreases. Interaction of single defect with a domain wall is investigated. It is found out that single defect being near a domain wall can be drawn by defects of a domain wall and is built in it. It is found out that in the course of embedding a part of defects in a domain wall are accelerated and leave forward along a domain wall, and other part of defects is braked, releasing a place for new defect.
June 24, 2020
May 29, 2020

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