Atomization processes of two-dimensional liquid sheets

Experiments were conducted to characterize the behavior of a two-dimensional liquid sheet exposed to a co-flowing gas. A wide range of flow conditions was explored. The parameters varied were the liquid velocity, gas velocity and liquid sheet thickness. The sheet was studied with co-flow present on one side, co-flow present on both sides and no co-flow. The gas co-flow was generated by gas jets parallel to the water sheet. The fluids used were water and nitrogen.; The study was motivated in part by the importance of two-dimensional sheets as baseline geometry for the large variety of liquid sheets geometries used in atomizers and in part by the scarcity of experimental data on two-dimensional sheet atomization. Specific motivation came from the application of sheet atomization to annular and swirl coaxial rocket injectors.; Several regimes of sheet behavior were defined based on the effects of the coflowing gas and on the state of the liquid sheet before the gas co-flow was added. The effect of fluid velocity and sheet thickness on the regimes was found to be satisfactorily accounted for by classifying the data in terms of liquid Reynolds number and a combination of the Weber number, Ohnesorge number and Reynolds number equal to We.Oh/Re. This result does not apply to all thicknesses studied in the case of turbulent water sheets. Cases where co-flow is present on one side of the sheet only were found to be qualitatively identical to cases with co-flow on both sides of the sheet.; When the sheet water sheet is not turbulent waves develop on the sheet and holes appear in the sheet due to the deformation and stretching of the waves. The growth of the holes eventually leads to breakup. In some cases, when the co-flow velocity is large the waves evolve into a network of crosstream and streamwise ligaments. For a few cases only streamwise ligaments were observed when the co-flow velocity was very high.; When the water sheet is turbulent a multitude of perforations develop in the sheet before any waves can grow, the growth of the perforations result in a network of ligaments which eventually breakup.; Breakup length measurements were taken. They were thoroughly compared to an existing correlation of the breakup length of two-dimensional liquid sheets subjected to a background gas flow instead of a co-flow from gas jets parallel to the sheet. The decrease of the gas velocity along the axis of the sheet in the current experiments with gas jet co-flow was found to be important parameter in the study of the breakup length. By assuming a gas velocity distribution similar to that of a wall jet and using some arguments about the momentum transfer between the gas and the liquid flow a relationship was established between the breakup length with background flow and the breakup length with jet co-flow.