0:12 [Music]
0:14 so here's a picture of the apparatus
0:17 from lab number four there's a water
0:22 flow from left to right and in this
0:24 experiment there's a piece of Plexiglas
0:27 on the side of the venturi flow meter so
0:28 that you can see the cross-sectional
0:32 area you can see the croc sectional area
0:34 gets reduced gradually to a minimum here
0:36 at what's called the throat which is the
0:39 point of maximum velocity and then as
0:42 the flow moves downstream you can see
0:44 that the cross sectional area of the
0:47 flow increases in the velocity will
0:49 decrease in this region
0:53 there's also seven pedometers here and
0:56 so we can actually make a measurement of
1:00 the hydraulic grade line see how high
1:02 the fluid rises in those pedometers and
1:06 compare that to what Bernoulli equation
1:10 would predict for an ideal inviscid flow
1:12 and that's one of the objectives of the
1:16 lab but it's nice today to show this in
1:18 in order to explain the concepts of
1:21 hydraulic grade line and energy grade
1:29 line for actual flows this is the
1:31 experimental setup for lab number four
1:34 you can see the venturi flow meter at
1:35 the bottom with the flow from left to
1:37 right so on the left hand side there's
1:41 this blue water tank and there's a
1:43 supply of water continuously to that
1:46 tank and the pipe that you see up here
1:49 is actually an overflow pipe so there's
1:52 water coming into the pipe and so the
1:53 water level in this tank will be
1:56 somewhere up around here and they'll be
2:01 continuous over a flow you can see the
2:04 venturi meter they're attached to the
2:09 bottom of the water tank there are as I
2:12 mentioned seven pedometers and in this
2:13 case I've add
2:15 a little bit of blue dye to the flow
2:17 just so you can see the heights of the
2:19 pedometers when you do the experiment
2:24 for lab 4 there won't be any dye and
2:26 there's a valve here just a hand valve
2:28 on the outlet that allows me to control
2:38 the flow rate through the system next
2:40 I'm going to show a short video
2:46 presentation of lap number 4 the venturi
2:50 flow meter and after I've shown the this
2:53 video we're going to look at the
2:56 analysis of the hydraulic grade line and
2:58 the energy grade line for this actual
3:01 flow now before I start the video you'll
3:04 notice here that there's no flow through
3:06 the venturi at the moment this valve
3:11 over here is closed and so all of the
3:13 pedometers here have fluid at the same
3:16 height they would be at equilibrium with
3:18 the fluid in the tank and so that
3:20 represents the fluid level in the tank
3:24 at the start so now let's just watch the video
3:36 so at the beginning here I'm just
3:39 opening that valve to let some flow
3:41 through and you'll notice the pedometer
4:00 now you can see it's pretty much a
4:04 steady state so you're seeing the
4:11 finally what I'm gonna do is just turn
4:23 and there it is with the flow off and
4:25 we're back to the original situation so
4:28 now there's no flow through the venturi
4:34 flow meter and all of the pedometers are
4:37 back to the original level the height of
4:40 the level in the adjacent tank and you
4:41 can see that because I drew a little bit
4:45 of flow the height of the water level in
