>> Okay, just a reminder, next Wednesday is our first midterm, okay? We'll talk
about that in about 40, 45, 50 minutes, last part of the class period. So, we'll
get to that. We are in chapter 5 of our text. Dimensional analysis and
similarity, our similar to studies. Go back and review real quick. We -- this
was a problem we looked at as an example. It was a drag force on a smooth
sphere. And we said that the drag force was a function of the velocity, the
viscosity, the density of the fluid and the diameter of the sphere. There were
five variables up there. There were three dimensions, M, L and T. 5 minus 3 is
2. There's two important dimension as parameters. And we identified those by the
pi theorem. And the pi theorem said the two important parameters here on the Y
axis, here on the X axis, this is called the drag coefficient. FD is a drag
force, drag coefficient. This was the Reynolds number. So, no matter what fluid
we've got, maybe the squares, what diameter we've got, what velocity we've got,
if we take wind tunnel data, for instance, and change those things, all the data
points appear to fall on a single line. Actually it comes down, it goes down
this way, from upper left to lower right, but that's okay. It falls on a single
line. The drag coefficient versus a Reynolds number. As a matter of fact, I'll
make it look very similar to one we've had before. So, let me just go ahead and
change this guy. Be a drag coefficient comes down. So, we can compare that to
another one here. This graph next to it. So, let's draw this guy here, he's like
this, okay. I'm not going to put all those symbols on there again, but you get
the point. No matter what you would do in the laboratory in the wind tunnel, all
your data points fall in a single line. Now, it's not new to you, but you hadn't
gone through chapter 5 yet in fluids one. In fluids one there's another set of
curves. Looks like this. It's called a Moody chart. And the interesting thing is
they're very similar. Now over here in the Moody chart this is laminar and this
is fully developed turbulent. And we found out that there's not a Moody chart
for air and a Moody chart for water and a Moody chart for oil and there's not a
Moody chart for a pipe diameter of 1 inch, 1 foot, 10 feet. No. One Moody chart
is good for everything. Wow, are you kidding me. One Moody chart is good for
everything? Yeah, sure is. So, no matter velocity in the pipe, no matter what
pipe diameter, no matter what the fluid is in the pipe, all the data falls on a
single straight line on log log graph paper. F is equal to 64 divided by the
Reynolds number. Here's a curve, wave chart, labeled smooth plane. Interesting.
There's just one line on a Moody chart. Is there another piece of paper which is
valid for air and one for water and one for a 1 inch pipe and one for 10 feet
pipe and one for water and one for oil, one for velocity 10, one for velocity
20, one for velocity of 50 feet per second? No. There's only one line. Does that
look similar to this? Of course it does. Of course it does. So, no matter if you
took data out the lab, you'd find all your data points fell on a single curve
like this. Wow, that's pretty impressive. One sheet of paper. A Moody chart for
everything we deal with just about. Over here, one sheet of paper. The drag
force on a cylinder or a sphere. Wow, that's pretty impressive. How do we do
stuff like that? Well, number one is, after we took experimental data, or
before, we identified what the important dimension those parameters were? And
that gave us a big hint to plot one versus the other. With this guy up here
these were two important dimension parameters. Drag coefficient, plot on the Y
axis. Reynolds number, plot on the X axis. Moody chart, you didn't know at the
time, but you were plotting dimensionless numbers on here. Friction factor
dimensionless on the Y axis. Reynolds number dimensions on the X axis. As a
matter of fact, carry it further, the pressure drop in a pipe is a function of
what's in the pipe row, what's in the pipe mu, the velocity in the pipe, the
diameter in the pipe, and, here it comes, the roughness of the pipe. Oh, yeah,
roughness. All these curves here are labeled E over D. Guess what E over D is.
Oh, I'll tell you. It's a dimensionless parameter. How many important
dimensionless parameters are on the Moody chart? Here they come. F is a function
of the Reynolds number and the relative roughness. Yep. So, we chart another
good example of a dimensionless plot. You can see we engineers -- dimensionless,
dimensionless, we like to plot things on dimensionless coordinates, okay. We're
good at that. Okay, so now, the next part of chapter 5. Some of those guys have
names. I told you drag coefficient, Reynolds number, relative roughness. So, I'm
going to take the Reynolds number as a start and look at that. So, the Reynolds
number. Row BL over mu. RVL over kinematic viscosity mu. L just stands for a
length. I don't care if it's a diameter or the length of a pipe or whatever, L
stands for characteristic length. Rewrite this guy. And so I'm going to rewrite
it like this. Multiplied by V, divide by V. Multiply by L, divide by L. Take 1
over L, divided by L. I didn't change anything. They all cancel out. When I do
that though, numerator becomes row B squared L squared. Denominator becomes mu V
over L times L squared. This numerator, row V squared L squared is like a what's
called a dynamic pressure. Multiplied by an area. Any time you square something
that's an area. If you square a length, that's an area. You might recall from
fluids one, dynamic pressure, row V squared divided by 2. So, row V squared is
proportionate to the dynamic pressure. And when you multiply a pressure by an
area, you know from fluids one, pressure's force over area times area, that's a
force. That's called the inertia force. Take the denominator. Mu V over L.
Multiplied by L squared. Mu V over L, it kind of looks like... That. Here's a
mu, there's a mu. A difference in U, there's a velocity. A difference in Y,
there's a length. Yeah, same thing. First parenthesis looks like a shear stress.
Okay, that's a stress. Viscous stress. Mu. Second term, L squared looks like an
area. Anytime you square a length you get an area. What's a stress? A stress is
a force over area. Okay, so force over area times area gives me force. This is
the viscous force. Viscous force. So, the Reynolds number could be interpreted
as the ratio of two forces. Inertia force. Over viscous forces. Let's take an
example of maybe an oil. Oil's are very viscous. They don't always move fast
like air in an HVAC duct like that. So, we know the oil has a big viscous force.
If the denominator is big, that means the Reynolds number is small. Of course,
if the Reynolds number is small with oil, we're probably in the viscous range of
the Moody chart. If we've got air going through an HVAC duct and you do this in
the fluids lab, you'll find out the Reynolds number is really really big, if
you've done it in the lab you know it. If you're in there now, you'll find out
on the HVAC duct in our fluids lab. Yeah, because in that duct with the air
coming through there there's a high inertia and air is not very viscous. So, if
air is not viscous this guy is small. If this guy is small, Reynolds number is
big. So, for air in an HVAC duct, we're out here somewhere. Big Reynolds number.
Oil in a pipeline, we're down here somewhere. Small Reynolds number. Now, take
another dimensionless number. Mock number. You can go through -- by the way,
just so we know what mock number is defined as, mock number is defined as V over
A. A is the called the local speed of sound. We'll get into that in great detail
in our next topic in fluids two, which will be compressible flow. But for right
now that's what the mock number is defined as V is the actual velocity of the
object, A is the speed of sound at the location where the object's located.
That's why it's called local. It means that's the speed of sound at the location
you're at. This turns out to be, if you go through the same kind of analysis we
go through here, we won't go through it again, but it's inertia forces. Divided
by elastic forces. The elastic forces are due to compressibility. That's the
mock number interpreted as a ratio of forces. Then -- Through number 3. Not the
fruity number. This -- French, you know, the food number. The food, like food,
food, Froude. Okay. Froude number. FR. It's equal to the ratio of inertia
forces. Divided by gravity forces. And, oh, by the way, it's equal to -- I'll
put it up here. Froude is defined as V squared over gravity G times some
characteristic length L. Oiler number. EU stands for the oiler number. It's
equal to delta P -- it's put down here, delta P over row V squared. Delta P over
row V squared. Some pressure difference divided by density, divided by velocity
squared. So, the oiler number can be interpreted as a ratio of pressure forces.
Divided by inertia forces. The last one we want to look at will be the weber
number. Not by the way the drag coefficient is just a takeoff of this guy down
here. I'll put it down here. Drag coefficient. They sometimes call capital CD
the drag coefficient. Drag coefficient is FD over row B squared, D squared.
What's pressure? A force over an area. Right here. So, replace that delta P with
a force over an area. There's the force, there's the area. Length squared,
diameter squared. So, they're the same thing. But they're dealing with pressure
drops or pressure changes. Then it's called the order number. Looking at drag
force on object, it's called the drag coefficient. Okay, weber number, weber WE
is equal to row V squared L squared over sigma. From fluids one, sigma is the
surface tension. And you can interpret the weber number as the ratio of two
forces, inertia force. Over the surface tension force. One of the important --
well, different times, different situations. You analyze a situation you have
and you say to yourself, "you know what, I think that parameter is important."
Pressure drop in a pipe. First thing you do, always, calculate the Reynolds
number. Is the flow laminar turbulent? Okay, what's important, the Reynolds
number. Flow over a sphere or a long cylinder. First thing you do, calculate the
Reynolds number, get the drag force. Okay, Reynolds number. High speed aircraft
flying at mach 1.5. This guy's important. Okay? Because at that Mach number the
compressibility affects are significant for air and a mach number greater than
.3, you better look at the compressibility affects. Less than .3 you can assume
it's incompressible, air's incompressible. The magic number for the Mach number,
incompressible versus compressible affects. If you've got bubbles and droplets,
you could design a new paint sprayer or a can of spray paint. What you don't
want when you have this spray can of paint, you're going to paint some sheet
here, okay. Psht, psht, psht, psht. You don't want it in big droplets because
it's going to run down and droplets on the thing. You don't want it in too fine
a mist because it will just blow away and end up on your ceiling or your floor
or your arm. No, you got to design that paint sprayer, that little nozzle to
spray out just the diameter you want of those paint droplets. Or maybe bubbles.
Okay? Bubbles and paint droplets, they all depend on surface tension to make the
little spherical bubbles and droplets. So, anything concerning that kind of
design you'd say, "I think the weber number's important." Oaky? Order number,
yeah, again, the pressure drop across something, a valve, a pressure drop across
some kind of a fitting, a Venturi tube, yeah, okay, that's important. Froude
number, gravity. You designed a peer for the Pacific Ocean, Redondo Beach. You
know that peer is going to be hit by waves and those waves hitting that peer
cause the water to go up. So, here's the peer in the water. When the wave hits
that peer, the water's going to go up and come back down again. Watch some
pictures of waves hitting peers. Well, what's going to happen? That peer pushed
water up. What was trying to pull it back down it again? Gravity. Gravity's
important. So, yeah, okay, I think if I'm designing that I think maybe the
Froude number's important. If I'm designing, let's say, say a barge being pushed
by a tugboat, a barge. Barges have a big flat front. The big flat front looks
like this on a barge. When the water hits that it goes up and comes back down
again. Oh, yeah. That barge had to push that water up against gravity and then
it came back down again. Well, what's important? The Froude number. The Reynolds
number? Not so important. The Reynolds number will tell us the drag force of
friction on the hull. But for most of these objects the big things is you're
raising tons of water by feet. What does that? Oh, the engine driving it. Do you
want that? Obviously not, you want to go faster. So, what do you do, you test
something in a water channel. And what do you try and equate? The Froude number.
That's important. So, every one of these has its importance in different parts
of our engineering situations. Okay. Table 5:2 in your textbook. There it is. In
the white textbook. There's 20 dimensionless parameters there. 20. You think we
engineers love dimensionless parameters? You better believe it. You better
believe it. We love dimensionless parameters. Wait to you get to heat transfer.
You might be in there now. When you get to convection heat transfer, every
important equation is written in terms of important dimensionless parameters.
Yeah. Friction factor equals 64 over Reynolds number. Yep, there it is, an
important equation from fluid [inaudible] fluids one. And there's other ones in
fluids two. But especially in convection heat transfer. Anyway, oh, yeah,
there's 20 of them listed here. I just put five on the board here. There's tons
of them. Why do we use them? For a darn good reason. They make life simple. Look
at those graphs. They make life simple for us. Okay, now, all this leads up to
what they call similitude. Our similarity studies. So, the last topic in this
chapter is similarity studies. And it's nothing new to you. I mean, you can
watch commercials and see models maybe of aircraft in a wind tunnel. You might
see the model of a car in a wind tunnel or a truck. So, yeah, we do a lot of
model studies, model studies. And to do that we got to follow very specific
rules. So, let's write down, first of all, what similitude is. Okay. In words.
Similitude is the therian art of predicting prototype performance from model
observations. Prototype is a thing you're studying, the real thing you're
studying. You want to model it in a lab and from that model in a lab you want to
predict how the prototype, the real thing is going to perform. It's not just a
whole theory, here's the words, theory and art. So, theory gives us some
background of that, but sometimes we have to kind of massage that and extend
that beyond just theory to see how the prototype will perform from taking model
observations. Okay, so, number 1, geometric similarity. I'll write these out in
words and we'll talk about them. Okay, you're into constructing models of
aircraft, so you go to hobby store and you pick out a model of an F18 plastic
model. Look at the box, it says, "172." You say, "Oh, okay, that's a good scale
model, I like that. I like that." What that means, of course, you know what it
means, but I'll remind you. What it means, of course, is the model is once
divided by 72 times as big as the real thing. Put them in inches, in inches. One
inch in the model is 72 inches in the real thing, prototypes a real thing. One
inch in the model. 72 inches is what? 6 feet? Yeah. 1 inch on your plastic model
is equivalent to 6 feet on the real F18. Okay. Everybody knows that. You buy a
model you want to know what the scale ratio is. It's on the box. You go to the
hobby store, it's on the box. Okay, so you got that. I'm not going to model --
let's say I dropped a sphere in oil, I'm not going to model that in the lab by
dropping a cube in oil. No, I'm not that crazy. Model and prototype are the same
shape. You want to model a sphere, drop a sphere. Okay, it's got to be the same
shape, obviously. Most of these things are fairly obvious, but some aren't. By a
constant scale factor, everything in the model is scale 1 to 72. The length of
the wings, the height of the aircraft, the diameter of the wheels, everything is
scaled by a constant scale factor. But be careful. You say, "Okay, well, I'm
going to model this in a wind tunnel." So, if this angle is 30 degrees, I think
I'll make the scale one 30 degrees divided by 72. Oh, my gosh, no, you don't
change the angles. You don't change the angles. Okay, the rule is them, change
-- here it is right here, there's a word, change the linear dimensions, but
don't change the angles. Okay, got it, got it. So, that's pretty basic stuff.
Let's go on to the more fluid stuff. Number two, kinematic similarity. Kinematic
talks about velocities, accelerations. A, velocity is at corresponding points.
In the two flows. Model and prototype. Or in the same direction. And are
related. By a constant scale factor. In magnitude. B, flow regimes must be the
same. You're not going to try and model laminar flow in a pipe, in a real pipe
by turbulent flow in your model pipe. That wouldn't make any sense. You're not
going to try and model an aircraft going up Mach 1.5 with a Cessna going up Mach
.1. No, that wouldn't make any sense. You want the same flow regime. Okay, that
makes sense. But the kinematic similarity is you want the velocity at
corresponding points, I'll make an example here, here's a small sphere, here's a
big sphere. Maybe this is the prototype, maybe this is the model, but just so
you know, most people think, oh, the model's always smaller. No, that's because
you're used to going to hobby store and seeing the boxes carrying the aircraft
at 1 to 72. Sometimes in the real world the model is actually bigger than the
prototype. But, okay, that's all right. It can go either way. But this is the
model. This is the prototype. Okay. Here are the streamlines. Here's the
velocity right here. Velocity model. This right here, here's the velocity of the
prototype. Notice where the black dot is compared to where the sphere is. See
that there, that distance and that distance? That's got to be this guy right
here, okay? That's got to be that guy. If it's a 1/72, this is one inch from the
surface, this is 72 from the surface. Because it says, "Corresponding points."
What that means is you got to use rule one to figure out if this is where I
measure with my pitot tube, the velocity and the wind tunnel on this model, then
that's where this velocity VP is going to be this distance for the prototype
sphere. And, by the way, of course, these are different numbers. See that
constant scale factor? It might be three to one. Maybe it's three to one. That
means the velocity of the prototype is three times the velocity of the model at
the corresponding point, here and there. Okay. Now, let's do the last one. The
last one is number three. Dynamic similarity. Dynamics talks about what? How
forces cause accelerations. So, what is dynamic then do for us? Okay, now we
talk about forces. What does kinematic tell us? Velocities. Okay, same thing,
there's only one rule now. At corresponding points again. Okay, forces, so I'm
going to do the same thing again. Here's the model. Here's the prototype. I'm
going to say a pressure force. Okay, so, if the flow is moving passed the
prototype and the model, there might be a pressure force on the model right
here. On the surface of the sphere or long cylinder. Okay, corresponding points.
If that's 45 degrees fro0m the front, corresponding point is 45 degrees from the
front. Okay, there it is. Keep reading. Identical kinds of forces, pressure
forces, are what parallel? Look at this line, look at this line. Yeah, those two
lines are parallel. That's what it means. Okay. So, now we've got what we call
similitude. Similitude. Between the model and the prototype. Okay, so, let's
continue on then with our example. So, I'm going to work the example over here.
Going right along with our discussion on the circular cylinder or the sphere,
I'm going to say we have a sphere in water. And let's see... Okay. Prototype and
model. Prototype. Velocity of the prototype is 5 feet per second. I want to find
the force on the prototype from my model studies. The force on the model is
measured to be 8 pounds force. I want to find what velocity I should set the air
in the model study. Or the water, pardon me. Oh, I'm sorry, it is air, excuse
me. So, that is air. The model is in air, prototype is in water. So, let's erase
that top thing. Okay. Now we got it. I don't know, maybe I'm going to drag a
sphere behind a ship. Instrumentation package. It's spherical in shape. I drag
it behind the ship. I want to know if the ship is going 5 feet per second, find
out miles per hour, knots, what's the drag force on the ship from towing that
sphere? But I'm going to test it in the wind tunnel with air. You can do that,
you can change the fluid, you can do that. Okay. So, I say to myself, "Gee, I
wonder what's important, what's an important dimensional parameter for a sphere
being dragged behind a ship." I was going to say, "You know what, it looks like
that picture right there." Yeah, yeah, that's right, it's Reynolds number. Okay.
Step one, because you have identified the important dimensions parameter, was it
the weber number, was it the Strouhal number, which is a vibrating wire in a
windstorm? Was it the Mach number? No, for a ship. Yeah, no, it's a Reynolds
number. Okay, so number one step, equate Reynolds number. Reynolds number model
equal, Reynolds number prototype. So, we have row B, D over mu model, equal row
B, D over mu prototype. These two guys here are testing the same diameter and
model prototype sphere. So, the diameter's the same. Diameter, diameter, cancel
out. I'm going to go over here to this now. So, I'm trying to find what the
velocity of the model, okay, there it is. Velocity of the model. New model over
new prototype. Times the velocity of the prototype. The model then, for the
model and the model in air 1.64 times 10 to the minus 4, for the viscosity and
viscosity. Prototypes in water for water, 0.93 times 10 to the minus 5. The
velocity of the prototype is 5 feet per second. So, the model velocity in the
wind tunnel, model is in air, wind tunnel, should be set to 88.2 feet per
second. Just to give you a measure of that, that's 60 miles an hour. So, you set
the wind tunnel to 60 mile an hour and then you measure the force on it. And the
force you'll get in your wind tunnel is 8 pounds. Okay, so now I need to know
the drag force in the model in the wind tunnel. I say, "Gosh, what do I equate
now?" You know. I got to find a parameter that has a drag force in it. Where
could that possibly be? There it is right there, drag coefficient. Step two,
equate. Step one, equate Reynolds number. Step two, equate drag coefficient. All
right, F sub D over row V squared, D squared, for the model. Equal F sub D over
row V squared, D squared of the prototype. It's the same size sphere. D is the
same. Cancel, cancel. I want the drag force on the real sphere being towed
behind the ship. Okay, the drag force on the prototype, which is this guy right
there, is equal to row of the prototype over row of the model, multiplied by V
of the prototype over V of the model, quantity squared. Multiplied by the force
on the drag force on the model. Okay. I go the back of the book and I get the
densities of air and water at the ambient temperature. 62.4. And for air, 0.075.
Multiply that by the velocity ratio. Velocity of the prototype was 5. Velocity
of the model was 88.2. Square that and multiply that by the drag of force on the
model times 8. The drag force on the prototype then comes out to be 21.4 pounds
force. So, in similarity studies, you're given a problem, you have to figure out
where the important dimensionless parameters I should be equating. In this
problem there, obviously the Reynolds number. Got it. That gave me one thing.
Velocity. Number two, the drag coefficient. Gave me drag force on the prototype.
Okay, now, let's try another one. This one -- well, I'll draw the picture first.
Okay. This one a one tenth scale model of a hydrofoil. Is tested in a water
channel. The model drag force -- Is measured to be -- Eight tenths of a pound.
At a speed of 20 feet per second. Find the speed and force for the prototype. It
says, "Neglect viscous effects in the problem statement." Okay. You know what a
hydrofoil is, okay, it's what an air foil. Air foil operates on air. A hydrofoil
operates in water. Hydro, water. Operates in water. So, the hydrofoil is like
here. You're skimming on the top of the water. Oh, yeah, they go fast. They go
fast. And I don't know, maybe it's an air craft, I don't know what [inaudible]
and I don't really care, because that's not part of the problem. There's an
aircraft with hydrofoil, okay? Aircraft body, not an aircraft, it's like a ship,
okay, so we'll make it like this, okay? Doesn't matter what's up there, we're
interested in that guy down there. Okay, let's try and -- we have to equate some
things, all right? Let's see, Mach number -- no, I don't think so, no, I don't
think so. Weber number -- no, there's no bubble and droplets. No, I don't think
so. Let me see. What was that one up there? It had gravity. Oh, yeah, when that
hydrofoil hits the water, the water's going to come up on the hydrofoil and it
will go back down like that. There's the waterline right there. It pushes the
water up in front of it. Okay, that gives it away. Froude number. Here's another
clue, another clue. The problem said, the statement of the problem said,
"Neglect viscous effects." What's viscous effects? There it is, Reynolds number,
Moody chart, X axis, Reynolds number. Why? Viscous effects. Drag coefficient, on
a smooth cylinder sphere. Yeah. That's friction. So, yeah, okay, we know now
this tells us, this statement tells us neglect the Reynolds number. This one
tells us equate the Froude number. By the way, if you don't know what a water
channel is, it's a -- we've got one down in the hydraulics, fluids hydraulics
lab. There's one in there. It belongs to civil engineering department. It's a
long plex in our account poly, it's a long Plexiglas rectangular shaped, about
this high, about this wide and water is pumped -- water goes down here, goes
into a big tank and it's pumped back to the start again. But what I'm going to
say here is, the water only fills part of the tank, up to that height. So, you
can test things like that in this water channel in the hydraulics lab. What --
how do you test this model in air? You go to a wind tunnel or you could put it
in water too, but you go to a wind tunnel typically. Okay? But in a wind tunnel
there's air from top to bottom. In a water channel water fills part of the
channel and then you have air up here and the water's down here and you put your
little model in here and then you get the drag force on it. That's called a
water channel. If you want to look at one, the fluids lab, it's in the civil
engineering side of the lab. It's probably from here to that wall there. And
it's this wide and it's this high and it carries water down the water channel.
Okay, that's just a side light. Okay, so, we go into here now and we said what
we're going to do. We're going to equate the Froude number. Step one. Okay, V
model over square root, LGL model, equal V prototype over the square root of L
prototype G. There's gravity in there. If I'm here in Pomona testing something
in our lab, then I'm going to say, "Okay, the hydrofoil's going to operate at a
location where G's the same." He chose Pacific Ocean. There's not a lot of
difference in G there, sea level, and G here in Pomona at 850 feet above sea
level. There's not much difference at all. You can neglect it. Normally then you
say, "Okay, I'm going to cancel those guys out." Now, if you're going to test
this thing in Denver, Colorado, mile high, you might want to throw in the G in
Denver and the G in Pomona. There might be a difference in G, but normally you
say the G's are the same for all intents and purposes. Okay, so I get V
prototype then. V prototype equals square root of 10 times V model, because 10
is the ratio of the scale model ratio and that comes out to be 63.2 feet per
second. Which means the prototype hydrofoil is about 43 miles an hour. 43 miles
an hour. And then, number two, of course, to get the drag force we always equate
the drag coefficient. So, now we equate the drag coefficient. Okay, F of the
model over row V model squared, D model squared, F of the prototype, row of the
prototype, V prototype squared, D prototype squared. And we're solving for the
force in the prototype. So, force in the prototype is equal to -- are they both
in water? Yeah, the hydrofoil operates in water and I've got the water in a
water channel. Yep, yep, same fluid, same fluid. Row, row cancels out. So, solve
for FP. So, FP is equal to LP over LM cubed times F model. So, that's equal to
the prototype is a 10 times a model length. Cubed times F model and F model, he
told us, eight tenths of a pound. So, that gives us a drag force of 800 pounds
on the hydrofoil. Okay. So, that gives us two examples of how to apply
similarity studies. I'm going to work one more next time, but I want to go over
a quick review before our midterm next Wednesday. Next Wednesday, okay. So,
we'll kind of stop on this now, this is not on the midterm, as you know. I'll go
through it in a minute, but this is not on the midterm. So, we'll stop now and
we'll pick this up, yeah, after the midterm. Okay. All right, so, let's talk
about the midterm. I think, I'm not sure I mentioned it to you, but I'll mention
it to you now. The data package that you'll have for the midterm is on
Blackboard right now. So, you can go to Blackboard website, you can see what's
on the data package, which is what you'll have. I'll give you a data package on
the -- at the exam time. You'll put your name on it, you'll use it for the exam,
you'll turn it in after the exam, I keep them. The second midterm I pass them
back to you, your name's on it, you can mark it up. That's why I do that. You
can mark it up. I pass it back to you for the second midterm, you use it for the
second midterm, you pass it back to me with your exam, I keep it. On the final I
pass the data package back to you, you use it, you pass it back to me with your
exam, final exam. Okay, so that data package is online, but don't copy it and
bring it here the exam day. I'm going to give you the same data package with
your name on it when you come in for the exam. Okay, there is a practice exam,
which will be online Blackboard website Friday at 6 pm. Friday at 6 pm, practice
exam. That gives you about five days to look at it. You can ask me questions,
okay, next Monday that way, office hour next week. So, plenty of time to review
that. That was the midterm from the fall, quarter 2017. You'll see what I gave
you for the midterm. Okay. There'll be three problems, okay? They'll be from all
the material up to dimensional analysis and similarity. So, it -- I'll go
through the topics, they're in the course syllabus. That includes pipes and
series and parallel. Okay? That includes pump graphs and how you find the
operating point of a pump in a system. And that includes -- includes specific
speed of pumps, it includes cavitation in pumps. We did problems in class on
that and you had homework on that. How you read those pump graphs, typically the
pump graphs give you the pump head versus flow rate. The efficiency versus flow
rate, the input power versus flow rate and sometimes the net positive suction
head versus flow rate. So, of course, know how to use all of that to solve
problems. And then we have pumps in series and parallel. Pumps and series, pumps
in parallel. If a problem appears to be iterative, if you make a guess on F and
you go through the problem one time and you check your F guesses and they don't
agree, all you say is, "I would repeat the above calculation with these new F
guesses until the F's converged." I would repeat the above calculations with
these new F guesses until the F's converged. But don't do any more iteration. Go
through it one time. With your next F guess you tell me, my next guess would be
F equal .020 for F 1 and F equal .025 for F 2. But don't do anymore work if it's
iterative problem. You can bring in one equation sheet, one sheet of paper, 8
and a ? by 11, both sides. Anything you want on there. Obviously, any equations
I've boxed on the board are important. Any equations you use for homework or I
used for an example problem in class, any equations you used for homework I'd
put them on your equation sheet. You can photocopy examples out of the textbook.
Homework examples, I don't care, put it on there. You can make things so small
they're postage stamp size and bring in a magnifying class, I don't care. Okay?
So, you can put anything you want on there. I parked my car in lot C, okay, in
case you get a mental block after the exam where you parked your car, you know.
So, you know, anything's legal, anything's legal on that sheet of paper. Okay.
Both sides, one sheet of paper. Three problems, 60, 70, 80, 90 minutes. That's a
lot of time, that's a lot of time. So, you shouldn't be rushed for time, okay,
number one. When I taught fluids two last quarter, I was in a 50 minute class.
Oh, that's not good. People stress out with that kind of class, because you're
always worried. I've only got 47 minutes left, I've got 39 minutes left and, you
know. This should be plenty of time to look at your work. My goal is you finish
it all and you have time to look it over one time, okay. That's my goal. All
right. So, yeah, there should be plenty of time for that. Okay, any questions on
that then? Okay, yes, ma'am?
>> Any of the tables that you've used in class will give us the information that
we need for the problem or should we have those on our sheet?
>> When you look at that data package online Blackboard, everything's there. If
there's something missing you think's important, put it on your equation sheet.
>> Okay.
>> I don't think there will be there. I put everything important I use in there,
tables, graphs, Moody chart, back of the book, you know, stuff for properties.
Yeah, it's all there. Really
>> Okay.
>> Yeah?
>> If we do the practice exam fine will we be okay for the exam?
>> Probably not.
>> Probably not?
>> I'm kidding. If you can do it you're probably ready to walk in that door next
Wednesday. Yeah, what I would do is -- that's a good point though. What I would
do is don't look at the answers. I got three pages of problems and then the
answers. Go over the answers and time yourself. Give yourself -- try it now,
because that's a 50 minute exam I gave them. Try for an hour, see what you do.
If you don't think, give yourself 15 more minutes and then you'll know how
you're doing. Yeah, okay. All right, so we'll see you then next Monday I guess,
huh? Right.
