[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.27,0:00:03.11,Default,,0000,0000,0000,,- Let's talk about the Venturi effect.
Dialogue: 0,0:00:03.11,0:00:05.69,Default,,0000,0000,0000,,This has to do with water or any fluid
Dialogue: 0,0:00:05.69,0:00:07.36,Default,,0000,0000,0000,,flowing through a pipe.
Dialogue: 0,0:00:07.36,0:00:10.26,Default,,0000,0000,0000,,And it turns out, let's say\Nthis water's flowing right here.
Dialogue: 0,0:00:10.26,0:00:13.74,Default,,0000,0000,0000,,Minding its own business, having\Na good day for that matter,
Dialogue: 0,0:00:13.74,0:00:16.13,Default,,0000,0000,0000,,when it meets a constriction.
Dialogue: 0,0:00:16.13,0:00:17.59,Default,,0000,0000,0000,,What's gonna happen here?
Dialogue: 0,0:00:17.59,0:00:19.36,Default,,0000,0000,0000,,Well, the water's gotta keep flowing,
Dialogue: 0,0:00:19.36,0:00:22.08,Default,,0000,0000,0000,,but it's gonna start flowing faster
Dialogue: 0,0:00:22.08,0:00:23.63,Default,,0000,0000,0000,,through the constricted region.
Dialogue: 0,0:00:23.63,0:00:26.15,Default,,0000,0000,0000,,And the reason is, well,\Nthere's a certain amount of
Dialogue: 0,0:00:26.15,0:00:28.10,Default,,0000,0000,0000,,fluid that's flowing through this pipe.
Dialogue: 0,0:00:28.10,0:00:32.02,Default,,0000,0000,0000,,Let's say all the fluid\Nin this region right here.
Dialogue: 0,0:00:32.02,0:00:34.40,Default,,0000,0000,0000,,Let's say this front part of the water.
Dialogue: 0,0:00:34.40,0:00:35.62,Default,,0000,0000,0000,,I mean, this whole thing's filled up,
Dialogue: 0,0:00:35.62,0:00:38.61,Default,,0000,0000,0000,,but just say this\Ncross-section of the water
Dialogue: 0,0:00:38.61,0:00:40.97,Default,,0000,0000,0000,,happened to make it from this back portion
Dialogue: 0,0:00:40.97,0:00:43.75,Default,,0000,0000,0000,,to this front portion in, I don't know,
Dialogue: 0,0:00:43.75,0:00:45.33,Default,,0000,0000,0000,,let's just say one second.
Dialogue: 0,0:00:45.33,0:00:49.58,Default,,0000,0000,0000,,So this entire volume\Nmoved through this section
Dialogue: 0,0:00:49.58,0:00:51.25,Default,,0000,0000,0000,,of the pipe in one second.
Dialogue: 0,0:00:51.25,0:00:54.68,Default,,0000,0000,0000,,Well, there's a law in physics\Nthat says that same volume's
Dialogue: 0,0:00:54.68,0:00:57.65,Default,,0000,0000,0000,,gotta make it through\Neach portion of this pipe.
Dialogue: 0,0:00:57.65,0:01:00.60,Default,,0000,0000,0000,,Because if it didn't, where's it gonna go?
Dialogue: 0,0:01:00.60,0:01:02.41,Default,,0000,0000,0000,,This pipe would have\Nto break or something.
Dialogue: 0,0:01:02.41,0:01:04.08,Default,,0000,0000,0000,,This water's gotta go somewhere.
Dialogue: 0,0:01:04.08,0:01:06.72,Default,,0000,0000,0000,,If that much flowed\Nthrough here in one second,
Dialogue: 0,0:01:06.72,0:01:08.51,Default,,0000,0000,0000,,then this much has to flow through this
Dialogue: 0,0:01:08.51,0:01:12.10,Default,,0000,0000,0000,,little tiny region in one second,
Dialogue: 0,0:01:12.10,0:01:15.10,Default,,0000,0000,0000,,but the only way that\Nthat's possible is for this
Dialogue: 0,0:01:15.10,0:01:16.98,Default,,0000,0000,0000,,front surface, instead\Nof just traveling from
Dialogue: 0,0:01:16.98,0:01:20.57,Default,,0000,0000,0000,,there to there in one\Nsecond, the front surface
Dialogue: 0,0:01:20.59,0:01:21.81,Default,,0000,0000,0000,,is gonna have to change it's shape.
Dialogue: 0,0:01:21.81,0:01:23.35,Default,,0000,0000,0000,,But the front part of\Nthe water's gonna have to
Dialogue: 0,0:01:23.35,0:01:26.53,Default,,0000,0000,0000,,travel from here to here\Nmaybe in 1/4 of a second
Dialogue: 0,0:01:26.53,0:01:29.19,Default,,0000,0000,0000,,because all of this has\Ngotta cram through here
Dialogue: 0,0:01:29.19,0:01:30.55,Default,,0000,0000,0000,,in the same amount of time.
Dialogue: 0,0:01:30.55,0:01:31.93,Default,,0000,0000,0000,,Because that water's\Nstill coming behind it.
Dialogue: 0,0:01:31.93,0:01:33.26,Default,,0000,0000,0000,,There's more water coming.
Dialogue: 0,0:01:33.26,0:01:36.35,Default,,0000,0000,0000,,And the volume flow rate\Nhas got to stay the same.
Dialogue: 0,0:01:36.35,0:01:39.06,Default,,0000,0000,0000,,The volume per time\Nflowing through one region
Dialogue: 0,0:01:39.06,0:01:41.09,Default,,0000,0000,0000,,of the pipe has got to be the same as
Dialogue: 0,0:01:41.09,0:01:44.72,Default,,0000,0000,0000,,the volume flow rate through\Nsome other region of the pipe
Dialogue: 0,0:01:44.72,0:01:46.89,Default,,0000,0000,0000,,because this water's got to go somewhere.
Dialogue: 0,0:01:46.89,0:01:48.80,Default,,0000,0000,0000,,It doesn't just disappear in here.
Dialogue: 0,0:01:48.80,0:01:50.29,Default,,0000,0000,0000,,It's gotta keep flowing.
Dialogue: 0,0:01:50.29,0:01:51.66,Default,,0000,0000,0000,,That means...
Dialogue: 0,0:01:51.66,0:01:54.82,Default,,0000,0000,0000,,The important part is\Nthe water flows faster
Dialogue: 0,0:01:54.82,0:01:56.61,Default,,0000,0000,0000,,through the constricted region.
Dialogue: 0,0:01:56.61,0:02:00.38,Default,,0000,0000,0000,,Sometimes much faster through\Nthe constricted region.
Dialogue: 0,0:02:00.38,0:02:03.68,Default,,0000,0000,0000,,The smaller this is compared\Nto this original radius,
Dialogue: 0,0:02:03.68,0:02:06.35,Default,,0000,0000,0000,,the faster the fluid\Nwill flow through here.
Dialogue: 0,0:02:06.35,0:02:07.65,Default,,0000,0000,0000,,Why do we care?
Dialogue: 0,0:02:07.65,0:02:12.65,Default,,0000,0000,0000,,Well, because faster moving\Nfluid also means lower pressure.
Dialogue: 0,0:02:13.76,0:02:16.58,Default,,0000,0000,0000,,Why does faster moving\Nfluid mean lower pressure?
Dialogue: 0,0:02:16.58,0:02:18.25,Default,,0000,0000,0000,,Well, if we look at\Nthe Bernoulli equation,
Dialogue: 0,0:02:18.25,0:02:23.25,Default,,0000,0000,0000,,Bernoulli's equation says\NP one plus row g h one
Dialogue: 0,0:02:24.61,0:02:29.47,Default,,0000,0000,0000,,plus 1/2 row v one squared
Dialogue: 0,0:02:29.47,0:02:34.47,Default,,0000,0000,0000,,equals P two plus row g h two
Dialogue: 0,0:02:34.68,0:02:38.60,Default,,0000,0000,0000,,plus 1/2 row v two squared.
Dialogue: 0,0:02:38.60,0:02:40.71,Default,,0000,0000,0000,,Oh my goodness this looks frightening,
Dialogue: 0,0:02:40.71,0:02:43.72,Default,,0000,0000,0000,,but look at P one, we just\Npick some point in the pipe.
Dialogue: 0,0:02:43.72,0:02:45.75,Default,,0000,0000,0000,,Let's just pick this point right here.
Dialogue: 0,0:02:45.75,0:02:47.45,Default,,0000,0000,0000,,We'll call that point one.
Dialogue: 0,0:02:47.45,0:02:50.84,Default,,0000,0000,0000,,So all these ones, this whole\Nside refers to that point.
Dialogue: 0,0:02:50.84,0:02:53.64,Default,,0000,0000,0000,,Let's just pick point two right here.
Dialogue: 0,0:02:53.64,0:02:55.28,Default,,0000,0000,0000,,All this whole side refers to that point.
Dialogue: 0,0:02:55.28,0:02:56.08,Default,,0000,0000,0000,,Now, notice something.
Dialogue: 0,0:02:56.08,0:02:59.35,Default,,0000,0000,0000,,These are basically the same height,
Dialogue: 0,0:02:59.91,0:03:02.09,Default,,0000,0000,0000,,and assume height's not\Nreally a big difference here.
Dialogue: 0,0:03:02.09,0:03:03.96,Default,,0000,0000,0000,,So let's cross out the heights,
Dialogue: 0,0:03:03.96,0:03:05.10,Default,,0000,0000,0000,,because they're the same heights.
Dialogue: 0,0:03:05.10,0:03:06.62,Default,,0000,0000,0000,,We don't have to worry about that.
Dialogue: 0,0:03:06.62,0:03:10.21,Default,,0000,0000,0000,,This says that, alright, if\Nthere's some pressure at one
Dialogue: 0,0:03:10.21,0:03:12.99,Default,,0000,0000,0000,,and some velocity of the water at one,
Dialogue: 0,0:03:12.99,0:03:15.10,Default,,0000,0000,0000,,you can plug those in\Nhere and get this side.
Dialogue: 0,0:03:15.10,0:03:15.94,Default,,0000,0000,0000,,And now look at over here.
Dialogue: 0,0:03:15.94,0:03:18.75,Default,,0000,0000,0000,,We know that the velocity\Nat two is bigger.
Dialogue: 0,0:03:18.75,0:03:20.37,Default,,0000,0000,0000,,We just said that, it\Nhas to be because the
Dialogue: 0,0:03:20.37,0:03:22.15,Default,,0000,0000,0000,,volume flow rate's got to stay the same.
Dialogue: 0,0:03:22.15,0:03:24.68,Default,,0000,0000,0000,,So this speeds up in here.
Dialogue: 0,0:03:24.68,0:03:27.44,Default,,0000,0000,0000,,So this is bigger, this quantity here.
Dialogue: 0,0:03:27.44,0:03:30.52,Default,,0000,0000,0000,,But we know the whole\Nthing equals this side.
Dialogue: 0,0:03:30.52,0:03:33.76,Default,,0000,0000,0000,,So if this term increased,\Nthat means that the pressure's
Dialogue: 0,0:03:33.76,0:03:36.52,Default,,0000,0000,0000,,got to decrease so that when they add up
Dialogue: 0,0:03:36.52,0:03:38.84,Default,,0000,0000,0000,,they get the same as this side over here.
Dialogue: 0,0:03:38.84,0:03:41.13,Default,,0000,0000,0000,,This is actually called\NBernoulli's Principle.
Dialogue: 0,0:03:41.13,0:03:43.19,Default,,0000,0000,0000,,Bernoulli's Principle\Nsays that when a fluid
Dialogue: 0,0:03:43.19,0:03:45.72,Default,,0000,0000,0000,,speeds up, it's pressure goes down.
Dialogue: 0,0:03:45.72,0:03:47.89,Default,,0000,0000,0000,,It's totally counter-intuitive.
Dialogue: 0,0:03:47.89,0:03:49.60,Default,,0000,0000,0000,,We always expect the opposite.
Dialogue: 0,0:03:49.60,0:03:52.32,Default,,0000,0000,0000,,We think fast moving fluid, that's gotta
Dialogue: 0,0:03:52.32,0:03:55.87,Default,,0000,0000,0000,,have a lot of pressure, but\Nit's the exact opposite.
Dialogue: 0,0:03:55.87,0:03:59.46,Default,,0000,0000,0000,,Fast moving fluid actually\Nhas a smaller pressure
Dialogue: 0,0:03:59.46,0:04:01.34,Default,,0000,0000,0000,,and it's due to Bernoulli's equation.
Dialogue: 0,0:04:01.34,0:04:03.63,Default,,0000,0000,0000,,And this is what causes\Nthe Venturi effect.
Dialogue: 0,0:04:03.63,0:04:05.89,Default,,0000,0000,0000,,The Venturi effect refers\Nto the fact that if you
Dialogue: 0,0:04:05.89,0:04:08.98,Default,,0000,0000,0000,,have a tube and you want\Na smaller pressure region,
Dialogue: 0,0:04:08.98,0:04:10.99,Default,,0000,0000,0000,,you want the pressure\Nto drop for some reason,
Dialogue: 0,0:04:10.99,0:04:13.62,Default,,0000,0000,0000,,which actually comes up in a lot of cases,
Dialogue: 0,0:04:13.62,0:04:16.19,Default,,0000,0000,0000,,just cause a narrow\Nconstriction in that tube.
Dialogue: 0,0:04:16.19,0:04:19.94,Default,,0000,0000,0000,,In this narrow constriction,\Nfaster moving fluid,
Dialogue: 0,0:04:19.94,0:04:21.58,Default,,0000,0000,0000,,and it'll cause a lower pressure.
Dialogue: 0,0:04:21.58,0:04:24.48,Default,,0000,0000,0000,,This is the idea behind\Nthe Venturi effect.
Dialogue: 0,0:04:24.48,0:04:26.60,Default,,0000,0000,0000,,So the Venturi effect basically says for
Dialogue: 0,0:04:26.60,0:04:30.25,Default,,0000,0000,0000,,a constriction in a pipe, you're\Ngonna get a lower pressure.
Dialogue: 0,0:04:30.25,0:04:32.24,Default,,0000,0000,0000,,While we're talking about fluid flow,
Dialogue: 0,0:04:32.24,0:04:34.49,Default,,0000,0000,0000,,we should talk about one more thing.
Dialogue: 0,0:04:34.49,0:04:36.81,Default,,0000,0000,0000,,Let me get rid of this here.
Dialogue: 0,0:04:36.81,0:04:38.75,Default,,0000,0000,0000,,Imagine you just had a brick wall
Dialogue: 0,0:04:38.75,0:04:40.59,Default,,0000,0000,0000,,with fluid flowing towards it.
Dialogue: 0,0:04:40.59,0:04:41.78,Default,,0000,0000,0000,,Maybe it's air here.
Dialogue: 0,0:04:41.78,0:04:45.88,Default,,0000,0000,0000,,So you've got some fluid\Nflowing towards this brick wall.
Dialogue: 0,0:04:45.88,0:04:47.91,Default,,0000,0000,0000,,This seems like a really dumb example of
Dialogue: 0,0:04:47.91,0:04:49.85,Default,,0000,0000,0000,,Bernoulli's principle\Nbut I'm going somewhere
Dialogue: 0,0:04:49.85,0:04:51.86,Default,,0000,0000,0000,,with this so stay with me.
Dialogue: 0,0:04:51.86,0:04:53.07,Default,,0000,0000,0000,,This is flowing towards here.
Dialogue: 0,0:04:53.07,0:04:54.15,Default,,0000,0000,0000,,What's going to happen?
Dialogue: 0,0:04:54.15,0:04:56.11,Default,,0000,0000,0000,,Well, it can't go through the wall.
Dialogue: 0,0:04:56.11,0:04:57.35,Default,,0000,0000,0000,,It's gotta go somewhere.
Dialogue: 0,0:04:57.35,0:05:00.32,Default,,0000,0000,0000,,Maybe this just goes up like that
Dialogue: 0,0:05:00.32,0:05:02.34,Default,,0000,0000,0000,,and this, you know, I'm gonna go this way.
Dialogue: 0,0:05:02.34,0:05:04.16,Default,,0000,0000,0000,,It's closer to go that way.
Dialogue: 0,0:05:04.16,0:05:05.91,Default,,0000,0000,0000,,This side maybe just goes down.
Dialogue: 0,0:05:05.91,0:05:07.95,Default,,0000,0000,0000,,This is actually kind of what happens.
Dialogue: 0,0:05:07.95,0:05:09.62,Default,,0000,0000,0000,,But there'll be a portion in the middle
Dialogue: 0,0:05:09.62,0:05:11.12,Default,,0000,0000,0000,,that basically just terminates.
Dialogue: 0,0:05:11.12,0:05:14.42,Default,,0000,0000,0000,,It hits here and kind of just gets stuck.
Dialogue: 0,0:05:14.42,0:05:17.17,Default,,0000,0000,0000,,So there'll be some air\Nright near here in the middle
Dialogue: 0,0:05:17.17,0:05:19.22,Default,,0000,0000,0000,,where it's just not moving.
Dialogue: 0,0:05:19.22,0:05:20.64,Default,,0000,0000,0000,,What if we wanted to\Nknow what the pressure
Dialogue: 0,0:05:20.64,0:05:24.33,Default,,0000,0000,0000,,was there, based on the variables\Ninvolved in this problem?
Dialogue: 0,0:05:24.33,0:05:26.88,Default,,0000,0000,0000,,We could use Bernoulli's equation again.
Dialogue: 0,0:05:26.88,0:05:30.11,Default,,0000,0000,0000,,Pick two points, let's\Npick this one, point one.
Dialogue: 0,0:05:30.11,0:05:32.68,Default,,0000,0000,0000,,Let's pick this one, point two.
Dialogue: 0,0:05:32.68,0:05:35.92,Default,,0000,0000,0000,,Use Bernoulli's equation, it says this,
Dialogue: 0,0:05:35.92,0:05:39.60,Default,,0000,0000,0000,,and again let's say these\Nare basically the same height
Dialogue: 0,0:05:39.60,0:05:41.90,Default,,0000,0000,0000,,so that height is not a big factor.
Dialogue: 0,0:05:41.90,0:05:43.75,Default,,0000,0000,0000,,And if these terms are the same,
Dialogue: 0,0:05:43.75,0:05:45.50,Default,,0000,0000,0000,,then we can just cross\Nthem out because we can
Dialogue: 0,0:05:45.50,0:05:48.72,Default,,0000,0000,0000,,subtract them from both\Nsides, they're identical.
Dialogue: 0,0:05:48.72,0:05:50.14,Default,,0000,0000,0000,,Now, what can we say?
Dialogue: 0,0:05:50.14,0:05:52.92,Default,,0000,0000,0000,,We know the velocity of the air at two.
Dialogue: 0,0:05:52.92,0:05:54.72,Default,,0000,0000,0000,,It's not moving, got stuck here.
Dialogue: 0,0:05:54.72,0:05:55.91,Default,,0000,0000,0000,,It got stagnant.
Dialogue: 0,0:05:55.91,0:05:58.44,Default,,0000,0000,0000,,And so v two is just zero.
Dialogue: 0,0:05:58.44,0:06:00.66,Default,,0000,0000,0000,,And we get this statement\Nthat the pressure
Dialogue: 0,0:06:00.66,0:06:05.66,Default,,0000,0000,0000,,at two, which is sometimes\Ncalled the stagnation pressure,
Dialogue: 0,0:06:06.14,0:06:08.71,Default,,0000,0000,0000,,so I'm gonna call it\Nthe stagnation pressure,
Dialogue: 0,0:06:08.71,0:06:12.27,Default,,0000,0000,0000,,because the air right here\Ngets stuck and it's not moving.
Dialogue: 0,0:06:12.27,0:06:14.82,Default,,0000,0000,0000,,You might object, you\Nmight say, "Wait, hold on.
Dialogue: 0,0:06:14.82,0:06:16.52,Default,,0000,0000,0000,,"I thought the air had to go somewhere?"
Dialogue: 0,0:06:16.52,0:06:17.93,Default,,0000,0000,0000,,Well, it's all going somewhere.
Dialogue: 0,0:06:17.93,0:06:22.38,Default,,0000,0000,0000,,The point is, there's some air\Nright here that gets stuck.
Dialogue: 0,0:06:22.38,0:06:25.44,Default,,0000,0000,0000,,It get stuck and air starts passing it by.
Dialogue: 0,0:06:25.44,0:06:27.35,Default,,0000,0000,0000,,And so, what's this pressure here?
Dialogue: 0,0:06:27.35,0:06:28.71,Default,,0000,0000,0000,,Well, up here we just read it off.
Dialogue: 0,0:06:28.71,0:06:30.23,Default,,0000,0000,0000,,All these went away.
Dialogue: 0,0:06:30.23,0:06:33.31,Default,,0000,0000,0000,,P two, which is what I'm\Ncalling the stagnation pressure,
Dialogue: 0,0:06:33.31,0:06:37.91,Default,,0000,0000,0000,,has gotta equal P one,\Nthe pressure over here,
Dialogue: 0,0:06:37.91,0:06:42.91,Default,,0000,0000,0000,,plus 1/2 row v one squared\Nand we get this formula.
Dialogue: 0,0:06:45.22,0:06:49.65,Default,,0000,0000,0000,,You might think, "Why\Nwould we care about this?
Dialogue: 0,0:06:49.65,0:06:53.50,Default,,0000,0000,0000,,"Who is regularly shooting\Nair at a brick wall?"
Dialogue: 0,0:06:53.50,0:06:55.74,Default,,0000,0000,0000,,People do it all the time,\Nbecause you can build
Dialogue: 0,0:06:55.74,0:06:59.54,Default,,0000,0000,0000,,a pretty important instrument\Nwith this called a Pitot tube.
Dialogue: 0,0:06:59.54,0:07:01.85,Default,,0000,0000,0000,,And the Pitot tube looks\Nsomething like this.
Dialogue: 0,0:07:01.85,0:07:02.97,Default,,0000,0000,0000,,Let's get rid of that.
Dialogue: 0,0:07:02.97,0:07:05.19,Default,,0000,0000,0000,,So why would someone use this system?
Dialogue: 0,0:07:05.19,0:07:07.23,Default,,0000,0000,0000,,It's called a Pitot tube.
Dialogue: 0,0:07:07.23,0:07:09.36,Default,,0000,0000,0000,,People use it to measure fluid velocity
Dialogue: 0,0:07:09.36,0:07:11.74,Default,,0000,0000,0000,,or, if you're moving through the fluid,
Dialogue: 0,0:07:11.74,0:07:14.65,Default,,0000,0000,0000,,it's a way to measure your\Nvelocity or your speed.
Dialogue: 0,0:07:14.65,0:07:16.90,Default,,0000,0000,0000,,So what happens is you've got this set up.
Dialogue: 0,0:07:16.90,0:07:17.95,Default,,0000,0000,0000,,Let's say you're in an airplane.
Dialogue: 0,0:07:17.95,0:07:19.18,Default,,0000,0000,0000,,You mount this on the airplane.
Dialogue: 0,0:07:19.18,0:07:22.13,Default,,0000,0000,0000,,You're flying through the\Nfluid, which is the air.
Dialogue: 0,0:07:22.13,0:07:26.38,Default,,0000,0000,0000,,So that mean air is rushing\Ntowards this section here.
Dialogue: 0,0:07:26.38,0:07:28.98,Default,,0000,0000,0000,,Rushing past you, let's say\Nyou're flying to the left.
Dialogue: 0,0:07:28.98,0:07:31.75,Default,,0000,0000,0000,,So you'll notice air flying past you.
Dialogue: 0,0:07:31.75,0:07:34.78,Default,,0000,0000,0000,,A Pitot tube always has\Nthis section that's facing
Dialogue: 0,0:07:34.78,0:07:37.48,Default,,0000,0000,0000,,into the wind or into the air.
Dialogue: 0,0:07:37.48,0:07:40.41,Default,,0000,0000,0000,,This air would be directed\Nstraight toward this region,
Dialogue: 0,0:07:40.41,0:07:43.71,Default,,0000,0000,0000,,and the key is this is\Nblocked off at the end.
Dialogue: 0,0:07:43.71,0:07:47.56,Default,,0000,0000,0000,,So there's air in here,\Nbut it can't be moving.
Dialogue: 0,0:07:47.56,0:07:50.18,Default,,0000,0000,0000,,The air in this section\Ncan't be moving all the way
Dialogue: 0,0:07:50.18,0:07:53.26,Default,,0000,0000,0000,,to the front because, I\Nmean, where's it gonna go?
Dialogue: 0,0:07:53.26,0:07:56.52,Default,,0000,0000,0000,,We just said if fluid flows\Nit, fluid's gotta flow out.
Dialogue: 0,0:07:56.52,0:07:57.89,Default,,0000,0000,0000,,There's no out here.
Dialogue: 0,0:07:57.89,0:07:59.27,Default,,0000,0000,0000,,And then there's another region.
Dialogue: 0,0:07:59.27,0:08:02.59,Default,,0000,0000,0000,,Up here you've got a second chamber
Dialogue: 0,0:08:02.60,0:08:04.56,Default,,0000,0000,0000,,where the air flows over the top.
Dialogue: 0,0:08:04.56,0:08:08.23,Default,,0000,0000,0000,,And this is directed at a\Nright angle to that air flow.
Dialogue: 0,0:08:08.23,0:08:09.17,Default,,0000,0000,0000,,You've got another chamber.
Dialogue: 0,0:08:09.17,0:08:11.88,Default,,0000,0000,0000,,And again, in here, fluid's not flowing.
Dialogue: 0,0:08:11.88,0:08:14.90,Default,,0000,0000,0000,,The key is this gives you a\Nway to determine the difference
Dialogue: 0,0:08:14.90,0:08:17.91,Default,,0000,0000,0000,,between the pressure here\Nand the pressure there.
Dialogue: 0,0:08:17.91,0:08:20.39,Default,,0000,0000,0000,,If you had some sort of membrane in here,
Dialogue: 0,0:08:20.39,0:08:24.24,Default,,0000,0000,0000,,something dividing these\Ntwo sections that could
Dialogue: 0,0:08:24.24,0:08:26.22,Default,,0000,0000,0000,,tell you the pressure differential, right?
Dialogue: 0,0:08:26.22,0:08:29.78,Default,,0000,0000,0000,,If the pressure on this\Nside is a little bigger
Dialogue: 0,0:08:29.78,0:08:33.50,Default,,0000,0000,0000,,than the pressure on this side,\Nand this would bow outward,
Dialogue: 0,0:08:33.50,0:08:37.01,Default,,0000,0000,0000,,one of these is measuring\Nthe pressure here
Dialogue: 0,0:08:37.01,0:08:40.12,Default,,0000,0000,0000,,and one of them is measuring\Nthe pressure there.
Dialogue: 0,0:08:40.12,0:08:40.72,Default,,0000,0000,0000,,What is the...
Dialogue: 0,0:08:40.72,0:08:43.32,Default,,0000,0000,0000,,Mathematically, what's the relationship?
Dialogue: 0,0:08:43.32,0:08:44.60,Default,,0000,0000,0000,,It's the one we just found.
Dialogue: 0,0:08:44.60,0:08:47.54,Default,,0000,0000,0000,,Right here, this is the\Nstagnation pressure, right?
Dialogue: 0,0:08:47.54,0:08:49.99,Default,,0000,0000,0000,,The air's not moving in\Nhere, it flowed straight in.
Dialogue: 0,0:08:49.99,0:08:52.23,Default,,0000,0000,0000,,We know the v is zero right here.
Dialogue: 0,0:08:52.23,0:08:57.23,Default,,0000,0000,0000,,And so the stagnation pressure\Nequals the pressure up here.
Dialogue: 0,0:08:59.08,0:09:01.59,Default,,0000,0000,0000,,Again, I'm assuming there's\Nvery little height difference.
Dialogue: 0,0:09:01.59,0:09:04.58,Default,,0000,0000,0000,,Let's say this is a very small device
Dialogue: 0,0:09:04.58,0:09:07.00,Default,,0000,0000,0000,,and it's not like 10 meters tall.
Dialogue: 0,0:09:07.00,0:09:09.92,Default,,0000,0000,0000,,So any height differences are minuscule,
Dialogue: 0,0:09:09.92,0:09:11.84,Default,,0000,0000,0000,,and we would just have\Nour same equation before.
Dialogue: 0,0:09:11.84,0:09:16.84,Default,,0000,0000,0000,,This would just equal the\Npressure plus 1/2 row v squared.
Dialogue: 0,0:09:18.100,0:09:20.75,Default,,0000,0000,0000,,And this is how you determine the velocity
Dialogue: 0,0:09:20.75,0:09:23.83,Default,,0000,0000,0000,,or the speed, because now we\Ncan just solve this for v.
Dialogue: 0,0:09:23.83,0:09:28.83,Default,,0000,0000,0000,,I'd get that v one equals P\Ns, the stagnation pressure,
Dialogue: 0,0:09:29.14,0:09:32.94,Default,,0000,0000,0000,,minus the pressure at\None, that whole thing,
Dialogue: 0,0:09:32.94,0:09:37.42,Default,,0000,0000,0000,,times two, divided by\Nthe density of the air
Dialogue: 0,0:09:37.42,0:09:38.70,Default,,0000,0000,0000,,and then a square root because you have to
Dialogue: 0,0:09:38.70,0:09:40.24,Default,,0000,0000,0000,,solve for the v one.
Dialogue: 0,0:09:40.24,0:09:43.58,Default,,0000,0000,0000,,So this device lets you determine this
Dialogue: 0,0:09:43.58,0:09:46.33,Default,,0000,0000,0000,,pressure differential right here, check.
Dialogue: 0,0:09:46.33,0:09:49.08,Default,,0000,0000,0000,,You need to know what\Nthe density of air is
Dialogue: 0,0:09:49.08,0:09:51.08,Default,,0000,0000,0000,,and this gives you a way to determine the
Dialogue: 0,0:09:51.08,0:09:53.67,Default,,0000,0000,0000,,velocity of the fluid, or in other words,
Dialogue: 0,0:09:53.67,0:09:57.61,Default,,0000,0000,0000,,the velocity of your aircraft\Nflying through the air.