Interaction of Separated Gas Flow with Thin Liquid Films

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ABSTRACTPROPOSAL NO.: CTS-0352135PRINCIPAL INVESTIGATOR: JAMES A. DRALLMEIERINSTITUTION: UNIVERSITY OF MISSOURI ROLLAINTERACTION OF SEPARATED GAS FLOW WITH THIN LIQUID FILMSThe dynamics of thin liquid films that develop on a solid surface and are driven by an adjacent gas flow have applications in many engineering problems and have been the subject of many studies. However, the separation of shear driven films from the solid surface due to a sudden expansion in geometry and the resulting atomization in the separated gas flow field, has received little attention. This complex interaction between the liquid film and the gas in separated flow is encountered in mixture preparation for spark ignition engines, as well as in atomizer design, refrigerant flows, and film drag over wetted surfaces. Prediction of the circumstances under which the film separates from the wall is the first vital step in modeling this interaction but current approaches are extremely limited. It is the objective of this program to develop an understanding of the dynamics between the coupled gas phase (separated/reattached flow) and liquid phase, along with the details of the dominant interfacial instabilities to the point that these processes can be modeled. Of particular interest is the prediction of film separation from the solid surface and its atomization as a function of gas phase velocity and wall angle. The goals of the proposed work are to identify, characterize and model the nature of the film separation and breakup process, using both flow visualization as well as quantitative measures of the gas flow field, liquid film and drop field. A unique test section is proposed which is designed to provide distinct control of the shear force driving the surface of the liquid film, the gas phase separation at the corner and the acceleration forces experienced by the liquid film at the corner. Multiple quantitative laser-based diagnostics will be used to characterize the gas and liquid flow fields. The modeling program, in parallel with the experimental program, will rely on established models for the gas phase and shear driven liquid film as well as a unique combination of film instability mechanisms and empirical correlations. To broaden the reach of the research programs, the principle investigators include teaming of undergraduates with graduate students. The undergraduates will be included in all aspects of the research and discovery process. For example, undergraduate students may be put in charge of a lower priority measurement such as a pressure or temperature measurement. Undergraduates will work with the faculty and graduate students in determining sensor specifications, purchasing, installation, data acquisition and analysis of results. Interested and capable undergraduate student will be encouraged to pursue graduate studies. The results of the research will be disseminated through the usual means of scientific journals, technical meetings, and seminars.