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DY: Fachverband Dynamik und Statistische Physik

DY 32: Fluid Dynamics

DY 32.9: Vortrag

Freitag, 26. März 2010, 12:15–12:30, H47

Stability and disintegration of liquid sheets — •Bernhard Heislbetz — DLR Lampoldshausen, Institut für Raumfahrtantriebe, D-74239 Hardthausen, Germany

The primary mechanism of liquid sheet disintegration is the growth of small disturbances on the initial flat surface of a free liquid sheet. These disturbances generate wavy structures i.e. symmetric or antisymmetric wave modes on the surfaces of the liquid sheet which increase and cause a periodical separation of ligament structures. The disintegration mechanism itself depends on various miscellaneous hydrodynamic and geometric control parameters. Thus theoretical investigations are necessary to narrow the parameter space and give a better understanding of the influence of these parameters on the fragmentation process of the liquid sheet. Therefore we present a stability analysis for liquid sheets moving with a constant velocity through a gaseous atmosphere. The analysis includes the derivation of dispersion relations for highly viscous Newtonian and non-Newtonian fluids. The non-Newtonian fluids were modelled as power-law fluids to incorporate the rheological properties and viscosity characteristic of shear-thinning liquids. We show numerical solutions related to the wave modes and determine the most unstable growth rates and the corresponding critical wave lengths as well as the sheet breakup length of both kinds of fluids.