Date of Graduation

2002

Document Type

Thesis

Degree Type

MS

Committee Chair

Wade W. Huebsch

Abstract

In computational modeling of fluid flow, the interaction between surface roughness and the flow field continues to be a challenging problem. In the aerospace community, the primary concern for aircraft performance is surface roughness on the leading-edge of an airfoil or wing which can adversely affect the design characteristics. There has been a great deal of research in this area including the affects on flow separation, roughness-induced transition, and heat transfer. However, many questions still exist with respect to the roughness-fluid interaction. One particular type of surface roughness that has become a critical area of research for aircraft designers is ice accretion. This type of roughness can develop and grow on exposed parts of the aircraft (particularly the wings) if favorable atmospheric conditions are encountered. Ice accretion can significantly degrade the performance and controllability of the aircraft and in extreme cases, lead to an airplane crash. In this study, two problems that are encountered when modeling flow past aircraft icing are addressed: the geometric modeling of the ice shape and adequate resolution of the flow field to capture the relevant flow physics. As a partial solution to modeling of the ice shape, a specialized method based on Fourier analysis has been developed. This allows the algorithm to use actual ice shapes, obtained from experiments, in the flow calculations. As a solution to the second problem, the flow solver focuses a majority of the resources on the leading edge region where ice accretes, instead of having to solve the flow field around the entire wing. This allows a fine-grid region to be placed in areas of interest, which can capture flow phenomena that a coarse grid may miss. To verify the validity of the solutions, several test cases were run and compared to previous work, including flow past an isolated roughness element and a NACA 0012 airfoil in a rapid pitch-up maneuver. The results from this work are rather promising for further studies. It has been shown that the Fourier analysis is a valid tool for geometric modeling of the ice shape. The use of real ice shapes for the flow calculations will enable more accurate results to be obtained for the aerodynamic performance calculations. In addition, the use of only a portion of the airfoil geometry for flow analysis has been validated, which helps to alleviate deficiencies in computer memory and processor speed, while still properly resolving the flow field.

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