P11TEP-7495
- Title: Study of the dynamics of drop and bubble formation in planar and axisymmetric configurations
- Reference: TEP-7495
- Funded by: Junta de Andalucía. Consejería de Innovación Ciencia y Empresa (Regional Goverment of Andalusia)
- Duration: 01/01/2012-31/12/2014
- Principal Investigator: Carlos Martínez-Bazán
- Number of researchers: 9
- Budget: 134,515.50 €
- Summary: This project aims to deepen the understanding of the physical mechanisms of drops and bubbles formation in order to apply it to design new devices to improve the efficiency of production systems in the industrial sector. In particular, we analyze the dynamics of drop and bubble formation in planar and axisymmetric configurations both experimental and numerically, as well as by using linear stability analysis. Therefore, bubble formation in planar sheets will be analyzed by describing in detail the transition from the jetting to the bubbling regime as a function of the air-water thickness ratio, their velocity ratio and the Weber number. The bubbling regime will be studied experimentally by analyzing images acquired with a high speed camera to determine the bubble formation frequency under different operating ranges. Moreover, the experimental work will be complemented by numerical simulations which will allow us to determine the temporal evolution of the pressure at the outlet of the injection nozzle according to the parameters mentioned. Finally, we will conduct a thorough linear stability analysis using realistic velocity profiles. The combination of experimental, numerical and analytical techniques will help us to develop simplified models to characterize the bubbling frequency and the size of the bubbles generated as a function of the control parameters. Regarding the generation of bubbles in axisymmetric configuration, it is planned to develop suitable numerical algorithms to describe the growing process and the subsequent breakup of bubbles injected through a submerged nozzle using open-source codes such as OpenFOAM or Gerris. The three-dimensional and transient numerical simulations will allow us to describe map of instability transitions occurring in the wake of the bubbles in its free rising depending on the control parameters. Traditionally, the process of bubble formation has been studied under conditions of constant feeding gas flow or constant supply pressure. However, since none of these conditions are guaranteed in bubble production systems used in the industry, we will study the dynamics of bubble formation under mixed conditions, where neither the flow and supply pressure keep constant. The numerical simulations will be complemented with an experimental study to be conducted by acquiring simultaneously with two high-speed cameras located in perpendicular planes. As a mechanism for controlling the frequency of formation of bubbles and, therefore, its size, we will consider the acoustical force of the gas stream in the injection chamber. Finally, we will study the generation of drops in jets subjected to stretching, analyzing the stability of the jet by using two-dimensional global modes, conducting controlled experiments and performing numerical simulations. This will allow us to characterize the hysteresis in the jetting-dripping transition and to study the drop generation in the jetting regime.
