 In this segment, what we're going to do, we're going to examine the question, why study fluid mechanics? Now, it turns out that fluid mechanics plays a very important role in our lives. It runs throughout our bodies, we breathe in air, that's a fluid, it governs the atmosphere of the earth. Life on earth is very much fluid dependent, but what we're going to do, we're going to take a look at a number of different applications where fluid mechanics is very important. We'll start off by transportation and we'll look at commercial aviation for the most part there. We'll then look at buoyancy driven flows. We'll then move on to atmospheric oceanic flows. We'll then take a look at flow instabilities and we'll conclude with some of the fun aspects of fluid mechanics and I'll call that entertaining flows. So, to begin with what we're going to do, let's take a look at transportation and as I mentioned we're going to be looking at aviation related civilian aviation transportation. So let's look at some video clips on that. So what you're looking at here is the engine of a 777, this is on taxi in Montreal and what you'll notice on the inlet to the engine, there's a light dusting of snow on the ground and you can see a vortex forming. That vortex is originating due to the swirl on the inlet to the engine due to the compressor blades that are spinning around and through the Helmholtz vortex theorems we know that vortex lines can either end on themselves like a smoke ring, they can go to infinity or they can end on a planar surface, a wall and so what we're seeing here is the last of those three where the vortex line is ending on the planar surface or the wall and the vortex then moves into the engine and then as we go off the snow the vortex disappears although it really is still there. This is another 777, this is on takeoff from Paris Charles de Gaulle and watch the inlet to the engine here, again the Boeing 777, you can see moisture because of the low pressure zone that is created on the inlet to the engine and depending upon atmospheric conditions this was kind of a rainy morning and consequently there is high humidity in the air so you can see the moisture and then watch on takeoff, watch above the wing and there you can see the low pressure zone above the wing and again a lot of moisture forming as the pressure goes low vapor forms in the air and you can then visualize it. This is a Boeing 767, it was a flight between Calgary and Norita Airport Tokyo or Japan and you can see here visualization which is quite rare, it's sometimes hard to see this but there is a shock wave that you can visualize through the optical technique called shadow graph, it just happened the angle of the sun was such that you could visualize the shock above the wing and there you can see the shock moving back and forth due to the changing of the inlet flow on the wing due to the turbulence as the aircraft is flying and so the shock wave is not stationary it moves back and forth in response to that. This is a flight from Reykjavik to Paris and what you can see here is an early morning flight and so the light conditions were quite favorable but you can see the contrails forming behind the jet exhaust so there is water vapor due to combustion and the water vapor the particles they form little droplets and then they freeze very quickly and that's what we call the contrails and so here you can see the contrails forming behind an aircraft flying over Calgary and if you watch what happens those contrails break up through the Crowwind stability. Again with the home holds vortex theorems the vortices have to close on themselves and they break up. This is a 747 on landing in Hong Kong International Airport you can see the leading edge trailing edge flaps fully deployed and then finally this is a 757 aircraft landing in Paris and you can see the landing gear deployed the flaps through the shadow and then as we turn to look at the wing the spoilers go up and the thrust reversers at that point would be deployed and the flaps are fully deployed as well in order to decelerate the aircraft. So those are a number of applications showing transportation applications of fluid mechanics and consequently we can see that there is an awful lot of fluid mechanics everywhere within those flows. The next one that we're going to look at is going to be buoyancy driven flows. Buoyancy driven flows are sometimes used in industrial processes sometimes they're used for other things so let's take a look at buoyancy driven flows. Here we have a clip of a smokestack in the middle of Medellin Columbia and this was a very very calm morning and consequently there was not a lot of turbulence within the planetary boundary layer and consequently you can see the smoke going straight up. This is a natural draft cooling tower in Germany. There you can see that it is being driven by the buoyancy of the hot gases the steam rising. This is a flame at a restaurant at Planet Hollywood in Las Vegas and the restaurant's name is Burger and you can see a little bit of a flame instability. This is with high speed video so it's kind of neat to be able to see that flame ripple around but it is caused by buoyancy. This is something that I like doing during the summer and barbecuing in the backyard to get to listen to a little bit of cold play here and you can see due to the index of refraction variations as the air heats up behind the barbecue you can visualize it and then as you go higher up in the barbecue there are some byproducts of combustion coming out which obviously would have different index of refraction as well and consequently you can visualize the flow. This is another buoyancy driven flow this was in front of the Sony building in Tokyo Japan and here you can see the heavier mist descending and then it hits the ground and then moves off to the right in a little bit of a jet and that would be another example of a buoyancy driven flow where it is going downwards instead of up and finally this is in the Toronto Pearson International Airport a neat little display they have there. The bubbles are causing circulation in this flow cell and the cubes you can see them moving due to the injection of the circulation due to the bubbles rising and that would be due to the buoyancy of the bubbles that was causing that to rise so that's a second type buoyancy driven flow the next one we're going to take a look at our atmospheric and oceanic flows so let's take a look at atmospheric oceanic flows and we're going to begin this is a video clip of Cascade Mountain in Banff which is near Calgary and you can see the wake of the mountain that the wind was coming and you can see the snow coming off the mountain you get a recirculation zone there this is a wind turbine that is being propelled by the wind in the planetary boundary layer this was in Germany beautiful apparatus structures that we see unless people live near them they sometimes complain but I find them beautiful this is an aquarium you can see a fish flowing through and bubbles and and this again is a high-speed video clip and what we're going to do in a second here we're going to zoom in on the bubbles and bubble flow is a very very interesting type of flow very important for the oceans because that's where the oxygen comes from but you can see the bubbles are flowing right behind one another and they get entrained in the wake of one another a very complex pattern and these are jellyfish these jellyfish are in the Maui Aquarium a beautiful display that they have with hundreds of jelly fish inside of this and and you can see the jellyfish moving around the propulsion that they have a very different type of propulsion system but very much fluid mechanic related and so a bio bioengineering inspired flow you could study the jellyfish and that as well would be fluid mechanics that you get to see in action there so that is atmospheric oceanic flows the next one we're going to take a look at flow instabilities now these are things that you don't always find and what's it all you do and it's kind of interesting when you do find them and so I'll show you a couple of examples and I've come across over the years we're going to begin at a park in Guangzhou China Bayou Park I believe was the name of it and here is a little fountain that they had and and if you listen you can hear the instability and the wind direction was from the right and when the wind would calm down and stop the way we go away when the wind slows down and it goes away for a very neat ability this is a Ford Fusion car and this had a cavity mode when you drive it and you get about 40 miles per hour it drives you crazy due to the noise but there's vortex shedding off the front of the window and then it impinges on the back of the window so listen to this you slow down the vortex shedding on the cavity gets lower and lower and so it goes away so those are two examples of flow instabilities the water park in China and then the Ford Fusion and and obviously that's not something that's desirable usually the engineers try to avoid it but sometimes you can't avoid it given the particular design of a vehicle and sometimes a sunroof will do that as well and that's why they sometimes have the vortex and break down device at the front of the sunroof to get rid of it last thing we're going to take a look at entertaining flows and so fluid mechanics can sometimes be highly entertaining I think it's always entertaining but let's take a look at that that's a moment and mark this is a room bubbles you can see the kids having a lot of fun trying to pop the bubbles and once in a while the bubbles do escape and you can trace and see what the fluid flow looks like and some bubbles aren't as lucky but this is video and we can fix that and bring the bubble back to life that this is Las Vegas the Bellagio Fountains very very impressive display of fluid mechanics at the Bellagio Fountains so that was some entertaining flows we we saw a fountain with the ball we saw bubbles in Rome and we saw the Bellagio Fountains so there you can see a number of different reasons of why we would want to study fluid mechanics we looked at transportation we looked at buoyancy driven flows a lot of industrial applications atmospheric oceanic flows very very important today with all of the concern about change in weather within in the earth's atmosphere flow instabilities those are sometimes rare but neat when you find them and then entertaining flows fluid mechanics make people happy and consequently I hope you can use this video segment as being a way to provide you with motivation for why you should study hard when you're studying fluid mechanics it's a very fascinating subject has many many applications in our everyday lives