Browsing by Subject "Droplet motion"

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Open Access
Isogeometric boundary element formulation for deformable particles in microchannel confinement
(2023-08) Gümüş, Özgür Can
Numerical simulations of deformable particles are essential to understand quantities that are not possible with experimental techniques. The boundary element method is an advantageous technique to analyze deformable particles in viscous flow conditions since it reduces the dimensionality of the problem by one for linear partial differential equations. Isogeometric boundary element formulation is proposed to model the motion of deformable particles which provides unique ad-vantages in terms of the higher-order continuity of elements and exact geometry representation. Moreover, it enables the calculation of surface normal and curvature analytically. Deformable particles, more specifically droplets, may undergo high deformation which deteriorates the mesh. Moreover, numerical inaccuracies result in a nonphysical change in the volume of the particle. Hence, volume correction and mesh relaxation algorithms are implemented in the isogeometric boundary element method to alleviate the aforementioned numerical artifacts. Without loss of generality, droplets in free and bounded flow cases are formulated and several benchmark problems are solved to assess the accuracy of the proposed formulation. Isogeometric boundary element method supported by stabilization methods explained in the study allows for obtaining stable and accurate results with low-resolution simulations.
Open Access
Modeling of droplet motion on textured surfaces
(2021-09) Naji, Mayssam
We describe the motion of a droplet on a textured ratchet track using a non-linear resonator model. A textured ratchet track is composed of semi-circular pillar array that induces a net surface tension gradient on a droplet placed on it. When a vertical vibration is applied, hysteresis is overcome, and the droplet moves towards the local lower energy barrier; however, due to the repetitive structure of texture, it keeps moving until the end of the track. The droplet motion depends on the amplitude and frequency of the vertical oscillation, and this dependence is nonlinear. Therefore, ﬁnding a fully analytical solution to represent this motion is not trivial. Consequently, the droplet motion still remains as a topic that needs further investigation. In this study we elaborate on the utility of double-pendulum as a basis for modeling the droplet motion on surfaces. Similar to the droplet motion, resonators, such as double pendulum, are simple, yet non-linear systems. Moreover, inverted double pendulum motion has key characteristics such as two phase motion and double peak motion, which are also observed in the droplet motion on textured ratchets. In this thesis, data processing models are developed to highlight the similarity between these two systems both qualitatively and quantitatively. After establishing this comparison, a model is proposed that utilizes an inverted double pendulum mounted on a moving cart to successfully simulate the motion of a droplet on a ratchet track. This methodology will lead to developing an accurate droplet-motion modeling approach which will be useful to understand droplet dynamics in more depth.