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Liquid crystal solitons in shear flows
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Resumo(s)
This thesis investigates the effects of shear flow on three-dimensional skyrmionic structures in liquid crystals. To conduct this study, computer simulations were developed and optimized in order to efficiently and correctly simulate the liquid crystal systems. Specifically, topologically protected structures such as the toron and the skyrmion tube were studied under both Couette and Poiseuille flows. To enable these simulations, a hybrid method was developed to accurately simulate the system, while taking into consideration the particularities of both the material flow and of the director field. Furthermore, the method was also adapted so that the simulations could use single-precision without losing accuracy in order to take advantage of the computation power of user grade GPUs. In the case of Poiseuille flow, it was observed that the toron and the tube behave similarly in the presence of flow, remaining very stable when low forces or velocities were imposed. For higher velocities, when using no-slip boundary conditions, the toron is destroyed and if partial slip conditions are applied the toron elongates, which was seen to be a reversible process with a characteristic time. On the other hand the tube remains stable even for high velocities. Moreover, the simulations with Couette flow showed that both structures have transverse motion relative to the imposed velocity, enabling us to visualize a skyrmion “Hall” effect in liquid crystal skyrmions. By studying this transverse motion of the structures under Couette flow, it was possible to realize that the angle of trajectory, ΘHA, is inversely proportional to the velocity imposed on the system. It was also seen that for low velocities, the structures move through space and time with constant shape and for higher velocities the tube elongates and the toron is destroyed.
Descrição
Tese de Mestrado, Física e Astrofísica, 2025, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Liquid Crystals Topology Skyrmions Hydrodynamics