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Two-phase Flow Modeling of Drop Impact on Moving Surfaces, Using Multiphase Lattice Boltzmann Flux Solver

Azadi, Ehsan | 2023

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 56865 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Tayyebi Rahni, Mohammad
  7. Abstract:
  8. Various situations of drop impact on solid surfaces occur widely in natural phenomena and industrial applications, as well as involve in the development of some new technologies, such as, 3D printers, interfacial materials, microfluidics, and biotechnology. Therefore, the relevant investigations have been increasing considerably in the last two decades. Most of these studies are related to the simple case of vertical drop impact on horizontal stationary surfaces, while in most cases vertical/oblique drop impact on horizontal/inclined stationary/moving surfaces in the absence/presence of a crossflow and their various combinations occur. One of the most important situations is drop impact on moving surfaces, which occurs in natural phenomena and industrial applications, as well as provides interesting opportunities for active control of drop impact dynamics. However, it has not been studied enough. The physics of drop impact on moving surfaces is affected by interaction of the drop with its surrounding gas and the moving solid surface, which often leads to asymmetric drop spreading. Moreover, the existing investigations on comparison of different situations of drop impact on solid surfaces are scattered and incomplete, because of the lack of a unified framework for representations and comparisons. Thus, the goals of this dissertation include: 1) further understanding of drop impact on moving surfaces, 2) development of a suitable framework for systematic comparison of different drop impact situations, and 3) determination of physical/technical opportunities of using surface movement for active control of drop impact on surfaces. To achieve these goals, numerical simulation of some drop impact situations was carried out, using multiphase lattice Boltzmann flux solver (MLBFS). This solver uses finite volume method for solving macroscopic Navier-Stokes and Cahn-Hilliard equations, while mesoscopic fluxes (determined by lattice Boltzmann method) are implemented. As a first innovation of this work, a unified transformation framework for analyzing, comparing, and classifying different situations of vertical/oblique drop impact on horizontal/inclined stationary/moving surfaces in the absence/presence of a crossflow and their various combinations was developed. Comparing the transformed versions of these drop impact situations facilitates identification of their physical similarities/differences and determines which situations (and under what conditions) lead to identical results and can be used interchangeably. Also, the possibility of symmetric drop spreading on moving surfaces was successfully achieved. Due to this interesting possibility, in related production lines or experimental setups (where symmetric drop spreading is required) the solid surfaces do not need to be stationary. In such applications, the use of moving surfaces can considerably accelerate drop impact processes. Based on the proposed transformation framework, 6 different 2D situations of vertical/oblique drop impact on horizontal/inclined stationary/moving surfaces in high density and viscosity ratios were simulated, using MLBFS. The related results well confirm the predictions and the possibilities of the unified transformation framework. Finally, the mass-conserved MLBFS was extended to simulate some 3D incompressible multiphase benchmark flows with large density and viscosity ratios of up to 1,000 and 100, respectively
  9. Keywords:
  10. Droplet Impact ; Solid Surface ; Moving Surface ; Unified Transformation Framework ; Symmetric Drop Spreading on Moving Surfaces ; Multiphase Lattice Boltzmann Flux Solver Method

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