Title: Modelling of shear-driven liquid wall films: effect of accelerated air flow on the film flow propagation

Authors: J. Ebner, P. Schober, O. Schafer, R. Koch, S. Wittig

Addresses: Lehrstuhl und Institut fur Thermische Stromungsmaschinen, Universitat Karlsruhe (TH), 76128 Karlsruhe, Germany. ' Lehrstuhl und Institut fur Thermische Stromungsmaschinen, Universitat Karlsruhe (TH), 76128 Karlsruhe, Germany. ' Lehrstuhl und Institut fur Thermische Stromungsmaschinen, Universitat Karlsruhe (TH), 76128 Karlsruhe, Germany. ' Lehrstuhl und Institut fur Thermische Stromungsmaschinen, Universitat Karlsruhe (TH), 76128 Karlsruhe, Germany. ' Lehrstuhl und Institut fur Thermische Stromungsmaschinen, Universitat Karlsruhe (TH), 76128 Karlsruhe, Germany

Abstract: Liquid wall films that are driven by the shear stress exerted from a co-current air stream occur in many technical systems, e.g. in rocket nozzles, heat exchangers and on steam turbine blades. They are also present in prefilming airblast atomisers which are used for the fuel preparation in modern aviation gas turbines. In many cases, an acceleration of the co-current air flow is imposed in order to improve the performance or because of the geometrical constraints in complex configurations. The film flow characteristics are strongly influenced by the additional pressure gradient and the associated increase of the interfacial shear forces at the gas-liquid interface. In order to predict the two-phase flow field, a model has been developed at the Institut fur Thermische Stromungsmaschinen (ITS), University of Karlsruhe (TH) which allows a fully coupled computation of the gas flow field and the liquid film. In the present paper the modifications are discussed which are required to take into account the effect of an imposed pressure gradient in the air flow on the film flow dynamics. It will be shown that the numerical approach is capable to predict the film propagation with a high accuracy, providing a powerful tool for the design and the improvement of technical applications where liquid film phenomena play an important role.

Keywords: shear-driven liquid film; numerical prediction; experimental set-up.

DOI: 10.1504/PCFD.2004.004086

Progress in Computational Fluid Dynamics, An International Journal, 2004 Vol.4 No.3/4/5, pp.183 - 190

Published online: 29 Mar 2004 *

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