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Numerical Simulation of the Impact of a Drop with a Flat Surface in a Cross Flow, Using LBM

Yazdani Dizicheh, Hamideh | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56003 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Taebi Rahni, Mohammad
  7. Abstract:
  8. In this research, numerical simulation of the impact of a drop on a flat surface with oblique velocity has been performed, using two-phase model of Lattice Boltzmann Method (conservative phase-field). During impact, it is important to investigate two-dimensional drop dynamics and to evaluate the effectiveness of the numerical method used. The model used here restores conservative phase field and preserves mass both locally and globally. In addition, to calculate the slope of the phase field, it calls the center points without engaging finite difference calculations. This makes it efficient for running parallel computations. A fixed dry and hard surface is considered and the drop impacts it at different angles (density ratio of the two fluids is 1000). The results are shown according to the angle of the drop velocity, when it impacts the surface obliquely at Weber numbers: 5, 10, 15, and 20 and impact angles: , at different times (from the moment of impact until reaching equilibrium). During impact, comparison of the effect of impact angle and Weber number on the change in the shape and asymmetry of the drop is conducted qualitatively in phases collision/spreading and collapsing. Collision angle, Weber, Ohnesorge, and Reynold numbers and also the mutual effect of Weber number and collision angle in changing the shape and symmetry of the droplet in two phases (collision/spreading and collapse) have been investigated. In collision and spread phase, the drop spreads almost symmetrically. When Weber number increases, asymmetry is resumed in drop shape. In collapsing phase, the change in the shape of the drop is completely affected and the amount of asymmetry in the collapsing phase increases with increase in collision angle. This means that, during impact, when Weber number increases, the asymmetry of the drop in collapsing phase is increased. These observations show the importance of Weber number and the greater effect of inertial force and impact speed (compared to collision angle for a micrometer-scale drop)
  9. Keywords:
  10. Multiphase Flow ; Lattice Boltzmann Method ; Cross Flow ; Oblique Impact ; Droplet Impact ; Conservative Phase-Field Model ; Numerical Simulation ; Oblique Drop Impact

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