A numerical study of fluid flow around two-dimensional lifting surfaces

342 Pages·1997·8.3 MB·English

by  Dannecker, John D

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.