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I3RARY m&VM DUATESCHOOL P DUDLEY KNOXLIBRARY NAVAL POSTGRADUATESCHOOL MONTEREY, CA93943-5101 A Numerical Study of Fluid Flow Around Two-Dimensional Lifting Surfaces by John D. Dannecker B.S. University of California, Berkeley, 1988 Submitted to the Department of Ocean Engineering and the Department of Mechanical Engineering in Partial Fulfillment of the Requirements for the Degrees of Naval Engineer and Master of Science in Mechanical Engineering at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY June 1997 ©1997 Massachusetts Institute of Technology All rights reserved nn A Numerical Study of Fluid Flow Around Two-Dimensional Lifting Surfaces by DUDLEY KNOX LIBRARY John D. Dannecker NAVAL POSTGRADUATE bCHOO! MONTEREY CA 93943-5101 Submitted to the Department of Ocean Engineering and the Department of Mechanical Engineering on May 9, 1997, in partial fulfillment ofthe requirements for the degrees of Naval Engineer and Master of Science in Mechanical Engineering Abstract There are always differences between theoretical and experimental results in the study of lifting surfaces. Bounding box control volume measurements infrequently yield exact conservation of mass or consistent values for lift and drag coefficients. Numerically calculated wakes often differ from experimental data. Quite often, an empirical correction can be applied to fit theory to experiment to account for these differences. However, as the demands for state of the art foil design increase, fluid dynamicists are pressed to look carefully at these inconsistencies in order to improve current design and analysis methods. Using a Reynolds Averaged Navier Stokes (RANS) computer code and a highly refined fluid mesh, one can begin to explore the subtle characteristics of the fluid flow in the entire domain and the details ofcertain key regions around a foil. Specific areas ofgreat interest are: flow around the trailing edge, flow within the boundary layer, wake profiles and the influence oftunnel wall boundaries in experimental facilities. The overall goal of this thesis is to resolve some of the discrepancies between theoretical results and experimental data. A computer code has been developed to generate the geometry for the fluid flow domain surrounding an arbitrary foil shape at a specified angle of attack in the MIT Marine Hydrodynamics Laboratory (MHL) water tunnel. This geometry is provided as input data for the RANS solver. A suite ofsoftware tools are developed to provide post processing analysis to compare the RANS solution with other numerical techniques and experimental measurements. Through the use of case studies, the numerical results of the RANS code are compared with recent MHL experimental data and other computational tools. A comparison is made between the experimental and RANS code results using a control volume analysis. Boundary layer and wake profiles are also compared. A correction scheme is developed to extrapolate experimental measurements to unbounded fluid flow. Thesis Supervisor: Justin E. Kerwin Title: Professor of Naval Architecture Thesis Supervisor: Douglas Hart Title: Professor of Mechanical Engineering Acknowledgments This thesis could not have been completed without the encouragement and support of my wife Michelle and my two children, David and Marina. I am eternally grateful for the patience and endurance during my studies here at MIT. I thank Professor Jake Kerwin for his gentle guidance and enthusiasm. To Scott Black, Todd Taylor, Gerard McHugh, Rich Kimball, and the many other Propnuts who pointed me in the right direction now and then. To Bill Milewski for pointing out to me that ninety percent of computational fluid dynamics is getting the geometry right. To Mr. Gordon Stevens, my high school physics teacher, who first taught me the importance of dimensional analysis and that science can be a lot of fun. Lastly, I am grateful to the United States Navy for providing the opportunity and funding for me to pursue higher education.