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  3. روش های نوین در سنتز S,N - هتروسیکل ها و دی تیوکاربامات ها با استفاده از مشتقات آمینی و کربن دی سولفید
مطالعه دینامیک غیرخطی جدایش و تشکیل قطرات - شبیه‌ سازی عددی با روش شبکه بولتزمن
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مطالعه دینامیک غیرخطی جدایش و تشکیل قطرات - شبیه‌ سازی عددی با روش شبکه بولتزمن

جعفری، یاسر Jafari, Yaser

Study of the Non-linear Dynamics of Drops Formation and Detachment -Computational Simulation, Using Lattice Boltzmann Method

Jafari, Yaser | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58738 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Taiebi Rahni, Mohammad; Salimi, Mohammad Reza
  7. Abstract:
  8. In this research, the non-linear dynamics of detachment and formation process of drops are investigated, using numerical simulations based on conservative phase-field model within lattice Boltzmann method. The motivation stems from the increasing need for a deeper understanding and precise control of this process to advance technologies such as inkjet printing, microfluidics (especially, aerospace applications), which, despite extensive studies, still face fundamental challenges. The objectives of this research include a detailed understanding of the mechanisms governing liquid fillament growth, pinch-off, detachment length and time, droplet volume, and fluid fillament stability, as well as the potential for active and passive control of the process via acoustic excitations and surfactants. The novelty of this research lies in comprehensive analysis of the interactions among viscous, gravitational, and surface forces, the prediction of non-linear (chaotic) behavior in successive drops dripping, the introduction of a new dimensionless parameter (JaTa) for forecasting satellite drop formation, and a systematic comparison of active and passive control strategies. The process is simulated in a periodic dripping regime in two dimensions for Newtonian, incompressible, and isothermal fluids, while the effects of key dimensionless numbers, including Reynolds, Bond, and Capillary, acoustic excitation, and surface tension reduction by surfactants are examined. The numerical method, based on conservative phase-field lattice Boltzmann method, employs two distribution functions for the phase field and hydrodynamics, enabling stable and accurate prediction of non-linear phenomena, such as pinch-off and transverse fluid fillament oscillations. The results indicate that increasing the Reynolds number reduces detachment time and increases droplet generation rate, whereas higher Bond and Capillary numbers lead to longer detachment intervals with lower drops production rates. Transverse fluid fillament oscillations play a significant role in secondary instabilities and highlight the limitations of axisymmetric flow assumption. On the other hand, acoustic excitation and the presence of SDS surfactant effectively enable control over drop detachment characteristics. Finally, the findings of this research can be applied in the design and optimization of related engineering systems
  9. Keywords:
  10. Drop Detachment ; Droplet Formation ; Lattice Boltzmann Method ; Conservative Phase-Field Model ; Acoustic Excitation ; Surfactants ; Satellite Droplet ; Nonlinear Drops Dynamics

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