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Experimental Investigation of Surfactant Effects on Dripping to Jetting Transition

Rouhipour, Ali | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57258 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Dehghani Firoozabadi, Bahar
  7. Abstract:
  8. Liquid droplets are a natural phenomenon with a wide applications in various fields, including food, pharmaceutical and agricultural industries. There are two regimes in the drop falling from a nozzle, dripping and jetting regimes. The size of the formed droplet and its geometry are influenced by the formation regime. One of the most challenging problems in this field is the transition from dripping regime to jetting regime. A common method of controlling of dripping to jetting transition ( DJT1 ) is the addition of surfactant. Surfactants are substances whose molecules have a hydrophobic tail and a hydrophilic head and reduce the surface tension of a liquid by adsorbing it. In this study, we experimentally investigate the transition from dripping to jetting regime in a Newtonian liquid containing surfactant. The ambient fluid is air and all experiments have been performed at a constant flow rate of drop phase fluid. Through image processing, we determine the droplet length and its volume ratio during detachment. First we examine the pure water and glycerol solutions in tract. Our results show that increasing the viscosity of droplet phase flow slows down the necking process and causes an increase in the drop length and a decrease in the volume ratio in the dripping regime at the moment of detachment. Also, by adding surfactant to the water-glycerol solution similar effects on the geometrical properties are revealed. Therefore, as the length of droplet increases, its volume ratio decreases. In addition, in jetting regime, by adding more glycerol to water and increasing the viscosity of the solution, the amplitude of Rayleigh instabilities waves slows down. This causes the jet to break up into drops of larger length. Similar results were observed for surfactant laden solutions. By adding surfactant to the solution, the capillary pressure that causes jet breakup is reduced and increases the length of the jet. The transition from dripping to jetting occurred at low flowrates by adding the viscosity of solution. Also, with the reduction surface tension due to the addition of surfactant, the driping to jetting transition occurred at low flowrates
  9. Keywords:
  10. Jetting Condition ; Surfactants ; Sodium Dodecyl Sulfate ; Surface Tension ; Dripping Regime ; Driping to Jetting Transition ; Experimental Investigation

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