12.800 Fluid Dynamics of the Atmosphere and Ocean
26 November 2001
Goal
This is an introduction to fluid dynamics intended
for first year graduate students. The goal is to help students
acquire an understanding of some of the basic concepts of
fluid dynamics that will be needed as a foundation for advanced
courses in atmospheric science, physical oceanography and
ocean engineering, among others. The emphasis will be on
fluid fundamentals having broad application:
- kinematics of fluid flow,
- conservation theorems,
- scaling and simplification procedures, and,
- problem definition, solution methods and interpretation
for simple flows.
Solution methods will include elementary numerical methods
for ODEs and PDEs. Example problems will be taken from
engineering as well as geophysical fluid dynamics.
Prerequisites It is presumed that students will have
had a course in classical mechanics and partial differential
equations, but no previous fluid dynamics. Students who
suspect that they may be significantly under or over prepared
should contact the instructor.
Schedule The class will meet on Monday, Wednesday and
Friday, 8:30-9:45, Rm 24-411 at MIT (subject to change
once the inevitable conflicts with other classes become
evident). Students who reside in Woods Hole should contact
the instructor as soon as possible regarding video tape
and P-tel options.
Resources The course has three main components: 1) class
meetings three times per week, mostly lectures, but including
some films. 2) reading assignments that will repeat some
lecture material, though with a different format or emphasis
and 3) homework problem sets.
Lectures
The lectures are intended to introduce key
concepts and to set them into the context of geophysical
problems. Formal lectures on fluid mechanics have the
potential to be stupefying. The instructor will do his
best to make the lectures interesting; the student's part
will be to ask questions and offer comments whenever a
clarification would be helpful. The lectures by themselves
would not constitute an adequate introduction to fluid
mechanics and must be supplemented by reading and by the
laboratory session.
Reading
We will make use of four textbooks. The primary
source will be Fluid Mechanics by P. Kundu and I. Cohen
(2001) (hereafter, KC01) which is recommended for purchase.
Three other useful texts are Atmosphere-Ocean Dynamics
by A. E. Gill (1982) (G82), Physical Fluid Dynamics by
D. J. Tritton (T88) and Mathematics Applied to Deterministic
Problems in the Natural Sciences by C. C. Lin and L. A.
Segel (1974) (LS74). For a few topics there will be an
additional, short reading assignment that can be recovered
from the web page (the first one is ELreps.pdf). The reading
assignments listed here are the minimum needed for a given
section or topic. We do not follow the order of KC01 and
the result is a rather chopped-up tour through the text.
You will find it more efficient to read larger pieces
of the text than are indicated here.
Homework
Homework will be assigned most weeks and
will be a significant factor in the grade. Homework assignments
will be made during the lecture and will be listed on
a web page, HWlog, that will be updated about one day
after each assignment. All aspects of an assignment may
be discussed with classmates; indeed, collaboration is
encouraged, but the final homework paper must be completed
by each class member individually. Five days will usually
be allowed to complete an assignment. If for any reason
a homework assignment can not be turned in on time, then
the student will have to make arrangement with the instructor.
Some assignments will require the use of a computer to
calculate and plot solutions. Students can use any programming
language, however Matlab is is recommended for those who
do not already have some facility with a programming language.
Matlab is widely used at MIT and WHOI and is a powerful,
flexible and very highly developed for scientific use.
MATLAB can also be very frustrating on first encounter
and novices are urged to spend a few hours with a Matlab
tutorial. Further help will be provided as needed to overcome
programming problems.
Exams and Grading There may be a mid-term examination,
and there will be a final examination to be scheduled
during the final exam period. Grading will be apportioned
roughly 40% exam(s) and 60% homework.
Syllabus
0. First Class Meeting. (Wednesday, 5 Sep
at 8:30, room 24-411 at MIT.)
- Goals of this class.
- Class administration; homework, exams, grades, etc.
- Scheduling options.
- Math review assignment.
Reading: K90, 2.1-2.3, 2.7-2.10, 2.13-2.16 Appendix B2.
For much more detail on these topics, see Boas, 1983.
1. A First Look at Fluid Mechanics. (approx.
one meeting.)
- Definition of a fluid and the continuum hypothesis.
- The laws of classical physics applied to fluid mechanics.
- Some classical and geophysical fluid problems; what
makes fluid dynamics challenging?
Reading: K90, 1.1-1.7. Highly recommended, T88 1, 5.1,
5.2, 26.
2. Kinematics of Fluid Flow. (approx. six
meetings.)
- Eulerian and Lagrangian representations of fluid flow.
- Trajectories, streaklines and streamlines.
- The material derivative.
- Reynolds transport theorem.
- Conservation of mass; divergence.
- Velocity gradient tensor and the Cauchy-Stokes theorem.
Reading: ELreps.pdf; KC01, 3.1-3.5, 4.1-4.3, 3.12-3.14,
2.4-2.5, 2.11-2.12, 3.6-3.14
Films: Flow Visualization
3. The Euler Fluid. (approx. six meetings.)
- Forces in fluids, pressure and buoyancy.
- Newton's laws applied to a perfect (Euler) fluid.
- Bernoulli functions.
- The circulation theorem and vorticity balances; Helmholtz
vortex theorems.
- Potential flows; Interacting potential vortices.
- Potential flow around an obstacle. §
Reading: KC01 4.7, 4.8, 4.16 - 4.18, 5.1, 5.2, 5.4, 5.5,
5.7.
Films: Pressure Fields and Flow Acceleration, Vorticity.
4. Earth's rotation. (approx. six meetings.)
- Earth's rotation and the Coriolis acceleration.
- Inertial motion, geostrophic motion, gradient flow
and Rossby number.
- Potential vorticity for a shallow fluid layer.
- Taylor-Proudman theorem.
Reading; KC01, 4.12, 5.6, 14.1 - 14.5, 14.8, 14.13. Highly
recommended, T88 16.1-16.5.
Films: Rotating Flows, Secondary Flows
5. Waves. (approx. five meetings.)
- Dispersion relation for inertia-gravity waves.
- An initial value problem.
- Energy propagation and group speed.
- Geostrophic adjustment.
Reading: KC01, 7.1-7.3; 7.9-7.10; 7.18-7.20; 14.8-14.15.
Highly recommended for c) and g) G88 5, 7.
Films: Waves in Fluids
6. Viscous Effects and Boundary Layers.
(approx. five meetings.)
- Tangential stress, the stress tensor.
- Constitutive relations, Newtonian fluids and the Navier-Stokes
eqns.
- Stokes first and second problems and Couette flow.
- Energy and vorticity balances.
- Scale analysis and dimensional analysis.
- Boundary layers; Blasius flow.
- Ekman layers and Ekman pumping.
- A first look at turbulence and Reynolds averaging.
Reading: KC01 4.5, 4.6, 4.10, 4.11, 8, 9.1-9.11, 9.15,
10.1-10.5. 14.6, 14.7 Highly recommended, T88 2, 5.6,
5.7, 8, 9 and for part e), LS74 6 and 7.
Films: Fundamentals of Boundary Layers, Flow Instabilities,
Turbulence
7. Final Examination, XXX.
References
Primary References: Reading assignments
will be made from these four texts. It is recommended that
you have a personal copy of at least K90.
KC01; Kundu, P. K. and I. M. Cohen, 2001.
Fluid Mechanics, Academic Press. (A complete and
well balanced introduction to fluid mechanics. Homework problems
will be assigned from this text.)
T88; Tritton, D. J., 1988. Physical
Fluid Dynamics. Oxford Univ. Press. (A physically motivated
discussion of fluid phenomenon that emphasizes the role of
experimentation and observation. Introduces turbulence from
the outset. )
G82; Gill, A. E., 1982. Atmosphere-Ocean
Dynamics. Academic Press. (A scholarly and extensive
introduction to ocean and atmosphere dynamics. Example problems
are motivated by observations, and carried through to interesting
results. Many tables of useful data.)
LS74; Lin, C. C. and L. A. Segel, 1974.
Mathematics Applied to Deterministic Problems in the Natural
Sciences. MacMillan Pub. (Part C is devoted to the theory
of continuous media, and is a precise, mathematical treatment
of continuum mechanics. A bit more formal than we want here,
but very valuable as a second, advanced source. Chapters 6
and 7 on scale analysis and simplification procedures are
superb.)
Fluid Dynamics/Applied Mathematics: There
are many useful textbooks and monographs that are relevent
to fluid dynamics. A few of those that are most likely to
be of use for this class and that are available from the instructor
or the Lindgren Library are listed below.
Acheson, D. J., 1990. Elementary Fluid Dynamics.
Oxford Univ. Press. (Concise and elegant treatment of mainly
engineering fluid dynamics.)
Aris, R., 1962. Vectors, Tensors and the Basic Equations
of Fluid Mechanics, Dover Pub. (Some of the opening chapters
are very clear and precise treatments of vector calculus,
etc. A bit advanced for a first course.)
Boas, M. L., 1983. Mathematical Methods in the Physical
Sciences. 2nd Ed., John Wiley. (This is perhaps the best
applied math reference at the level of senior undergraduate.
Excellent chapters on vector and tensor analysis and coordinate
transformations.)
Cushman-Roisin, B., 1994. Introduction to Geophysical
Fluid Dynamics. Prentice Hall. (Very clear introduction
to GFD.)
Farlow, S. J., 1993. Partial Differential Equations for
Scientists and Engineers. Dover. (This is a valuable
resource for those needing to refresh or extend their working
knowledge of PDEs.)
Holton, J. R., 1992: An Introduction to Dynamic Meteorology,
3rd Ed., Academic Press. (An excellent text covering
many aspects of atmospheric science. The early chapters are
a clear and concise introduction to fluid dynamics at just
about the level one can expect to remember. A good book for
ocean and atmospheric science students to own.)
Pedlosky, J., 1987. Geophysical Fluid Dynamics, 2nd Ed.,
Springer-Verlag. (This is the standard for GFD, though a little
advanced for a first course in fluid mechanics.)
Wilcox, D. C., 2000. Basic Fluid Mechanic, 2nd Ed. DCW
Industries. (This is an excellent introduction to fluid
mechanics. Where it overlaps K90 and KC01 it is often superior
in clarity and depth. The emphasis is on engineering (very
little on waves and geophysical flows) or this would be our
primary reference.)
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