Direct numerical simulation of a spatially developing water sheet at moderate Reynolds number

Although the number of publications in the area of two phase flows increases, there are only a few DNS studies concerned with the primary breakup of a spatially developing liquid film. This is probably due to the fact that often high density ratios and capillary forces lead to serious numerical problems. In addition, prescribing realistic velocity inlet data at the inflow boundary requires a sophisticated procedure in order to obtain physically realistic results. Therefore this paper focuses on a three-dimensional, spatially developing direct numerical simulation (DNS) of a liquid sheet exhausting into a gaseous atmosphere. Special attention will be paid to the validation of the code and the verification of the results. Flow and interface statistics in the near nozzle region of the liquid water film will be presented. In this region first instabilities develop which subsequently grow and finally can lead to the breakup of the film. It is very difficult to obtain such data experimentally. Finally the question is investigated if and how far the results of 3D and 2D simulations are comparable, the latter being attractive in view of saving computing time.