Hi! Welcome to fluid dynamics! in this
video I would like to go through the
most important things you need to know
about this course, and talk a little bit
about what we're trying to achieve with
the course overall. My name is Olivier,
Olivier Cleynen. I am a PhD student here
at the University Otto von Guericke of
Magdeburg, and I work in the LSS lab,
the fluid mechanics lab at the
University. Please just call me
Olivier — by my first name, Olivier. I'm
neither a professor, nor a doctor, or at
least not yet a doctor. There are four
channels with which we're going to
communicate through this whole whole
semester. The course is completely online,
so we'll never ever meet in person in a
physical room. The first channel is email.
I'm going to write to you a mail every
week with links to the new, newly-
released content, the new quizzes and the
homework that you will get throughout
the semester. The second channel is the
Moodle page, the Moodle page in the
e-learning website of the University. And
the course number is seven one nine nine
you should definitely go there and
register for the course over there
because over there we'll have course—
we'll have quizzes and there's also
discussion forums on which you can log in,
ask questions and get answers from
myself and from other peers. The third
channel is the course website which has
a hard to un-remember URL:
fluidmech.ninja . And on that website I will
release one new chapter every week for
the whole semester. There are 11 chapters
and every Thursday they will be one new
chapter released. And finally the last
channel is Zoom. Because if you want to
talk with me directly and get directly
answers and in a synchronous manner, you
can call me on Zoom every Friday
afternoon. You should definitely go and
check out the syllabus —the syllabus is
basically an explanation of what the
course is about, what the rules of the
course are, how its assessed— and I wrote
everything over there as clearly and as
friendly as I could
and you should definitely go and check
out everything you want to learn about
the course over there. The assessment is
the last thing I will talk about before
we move on to the content of the course.
Assessment this is really important to
you and it's really important to me. And
so there will be three things that will
add up to your final grade for this
course
The first thing is quizzes. We'll have
quizzes every week so every new chapter
there will be one new quiz. And all the
grades of all your quizzes together, that
amounts to 10% of your final mark. There
is going to be homework 4 times in
during the semester, and I will send this
homework to you by email. You will get
one personalized version of every
homework to do
and [need] to send me back by email four
times during the semester. And finally
40% are left for the final exam which
will happen at the end of the semester,
at a date that at the moment, when as a
record, I do not know. Perhaps in July,
perhaps in September. And this exam is
purely based, entirely based on problem
exercises that we go through during the
year. The course content has 11
chapters and perhaps as the diagram here
shows they are not all equally important.
I don't want to go through with every
detail of this plan but I'll just point
out that there are two branches.
Basically where we start on the top with
basic flow quantities and then we go on
to analysis of existing flows. This is
where we know what the flow is, and we
try to calculate things out of it.
And then we'll stop there and we'll
branch back out here to 4 5 6. And in
chapter 6 we try to predict what the
flow will be, so there's a much harder
endeavor. And once we're done through
this we'll go through a few interesting
chapters on specific topics from 7 to 11.
let me try to show you a little bit
what's inside the course. What's coming
up. Chapters two and three are analysis of
existing flows.
This is basically flows where
there is only two arrows one coming in
one coming out and we try to figure out what
forces or power exchanges are
involved. So to give you one example if
you have a pipe with water shooting
out of the pipe, there might be a force
exerting on the pipe holder. And in
this chapter we'll learn to quantify
those things. On the other branch, at the
branch where we try to predict flows,
we're trying to predict in general terms
where the fluid is going to go, and
that's a much harder endeavor. And we'll
start very slowly, very easily with fluid
statics, pressure distribution inside
fluids, and we'll move on to shear and
we'll add this up to write the
Navier-Stokes equation and this will
allow us to see how it is that engineers
and scientists predict the flow field in
much more complex situations. We
won't actually calculate this flow but
we'll see how it is made in practice, and
this should give you the basis to go
through then a course on computational
fluid dynamics later, after this course.
So you will see how computers
calculate the movement of fluids in
general. And once we're done with this
we'll go through a bunch of different
themes like pipe flows and engineering
models where we have small scale and
large scale flows. So for example we'll
take a look at pipe flows. Pipe flows may
look a little bit boring if you look at
this picture but can be pretty
enlightening in practice because there's
a lot to see and to learn about the
way water flows inside a simple pipe.
we'll learn to scale models up and down
for engineering purposes and will look
in detail into very small-scale flows
like for example this turbulent boundary
layer, and we'll look a little bit at how
engineers model much larger-scale flows
like this tornado here with the flow
field in a tornado. The objectives of
the course are twofold
(for you yeah they're onefold for me) I
would like you at the end of the course
to understand what can and cannot be
done
to mechanics so you are prepared for a
CFD (computational fluid dynamics) course
after that so I want you to feel for
what is possible to solve and what's not
possible to solve in fluid mechanics. The
second objective is that you can solve
real-world engineering problems with
confidence. Not every problem but a range
of different selected problems in the
end. And my objective in this is to get
you there with the minimum of your time
and energy for this. So very important a
minimum of time and minimum of energy
doesn't mean that the ratio of energy
per time is minimum. In other words you
need a lot of power and you need to work
pretty hard to go through this but I'll
try to minimize your overall time and
your overall energy to get through this.
Before we close up I'd like to say
a few things about how difficult and how
awesome fluid mechanics is. Overall there's
no doubt that fluid mechanics is super
difficult. And doesn't mean that this
course is difficult, it means that the
discipline fluid dynamics is
difficult. Now let me show you why a
little bit. Let's imagine you're standing
next to the sea in the summer and it's
nice and hot and warm and just see the
water flowing by and what you're
looking at is just simply the waves
crashing in onto the reef and they go
back and forth and a splash in and out
and you have this beautiful, amazingly
beautiful motion that's splashing in and
out in front of your very eyes yes like
so and you look at the waves moving about,
and now I’d like you to imagine you
calculated this. You have in some way,
that's not important to us right now, you
have calculated the position and the
velocity of the water droplets inside
this wave here and you know that you
have this in your head. The question is
how do you write it down? How do you
express it and how do you, from that
information, go to the next milliseconds
and
seconds after that, where this wave will
crash in all kinds of interesting
manners into the sea? So what I would
like you to think about is this. Even
before we describe the problem, the
equations that we're going to solve,
imagine just having the solution of it,
yes, and imagine how incredibly
complicated this solution is. And this is
how difficult fluid mechanics is. In
practice fluid mechanics is difficult for
humans. A simple question such as "will it
rain exactly two weeks from now?", on the
same day as today, will it be raining
today here or not? is a very difficult
question in practice. And there are
plenty of questions like this. Is the
next hurricane going to make landfall?
You can see newscasters screaming, left
and right, is the hurricane going left,
is it going right?  should we evacuate, should we
not evacuate? this is extremely hard to
calculate, extremely hard to predict. And
questions such as "how will the next
airplane fly?" You know Airbus and Boeing
have billions of dollars to invest when
they develop a new airplane, and they're
still building little models of it that
they put in wind tunnels to see how they
fly, how well or how poorly they fly,
because it's extremely hard to predict
how the flow will go around any given
machine. So, in this course we shall have
no illusions, yes? We develop a
methodology for finding solutions, so I
want you to see how fluid dynamicists
work, but at the end of the course I hope
you will be fully aware that not all
fluid mechanics problems can be solved
analytically, yeah? So we have to know the
limits of our understanding of the
mechanics. And before we close up I would
like also to convince you that fluid
mechanics is absolutely awesome. And you
may be thinking, well that's easy to say,
and I would quite agree.
So before I did fluid mechanics, I did
thermodynamics, and in thermodynamics I
used to say to students, I used to have a
slide that said "thermodynamics is the
most important discipline you will ever
study".
"thermodynamics is at the heart of our
civilization today". "Without
thermodynamics the world as you know it
would be completely different". And I
meant this, it's really true what's
written in here. And I thought well I
could just recycle this slide, you know? I
just swapped "thermodynamics" for "fluid mechanics", and it still works, but then of
course comes the thought "well if it works for thermodynamics and fluid
mechanics, what else does it work for?" And you could really easily swap this for
"Bacteriology", it works! "Bacteriology is at
the heart of our civilization today".
"Without bacteriology the world as you
know it would be completely different."
Totally works. So in practice you could
really have just $discipline variable
and just replace that variable
with whatever your discipline is, as you
need. So when I say "fluid mechanics is
awesome" you might be just thinking
"you're just paid to do this, to say that,
and to think this", and so it just totally
makes sense, so I'm not gonna say this.
I'm gonna say "fluid mechanics is awesome
because", I will give you a reason for
that. And the reason is, it is the only
discipline I know where your professor,
when he or she will look over your work
and at your screen with your displayed
results, they will say "hmm! I didn't think
the fluid would do that!" and that's
totally awesome. Because somebody who's
been through every corner of their
discipline for the last 20 years working
with every tool available to investigate
the motion of fluids will look at your
newly, newly- calculated flow or
your newly-measured flow, and will still
be amused and surprised by it. And that
is quite awesome, I think. So I would like
to say that fluid mechanics is awesome
because it's complicated enough to be
interesting, it's kind of fascinating
when you look at it but still not remote
space physics or particle physics or
anything else, it's still close enough to
be experienced every day when you open
the window and you look at the sky.
So welcome! I look forward to work with you,
and see you around in the e-learning
course. See you later.
