Controlling Turbulence and Evolution: How Engineers Overcome Uncertainty

[Music] I explore in this video how Engineers work their way around uncertainty because Engineers sell practical problems before they have full scientific knowledge I start with one of the most complex phenomena in nature yet one of utmost importance to Engineers as seen when smoke rises from burning incense the smoke exposes the movement of the air as heat from the incense drives the air to rise the issuing smoke reveals two types of flow near the incense the smoke wavers a bit the flow is smooth and even this is called laminar of low if we move up the spoke stream we see that the smooth stream becomes chaotic that churning flow is called turbulent to this day a fundamental understanding of when that transition from laminar to turbulent flow occurs puzzles scientists yet Engineers must know when the transition occurs to control which type of flow occurs of prime importance is the smooth laminar flow of air over an aircraft wing yet without a fundamental scientific understanding of how to achieve that laminar flow we've flown across the Atlantic Ocean routinely since the first commercial passenger flights in 1939 although 21st century science cannot fully understand turbulence a 19th century engineering Professor Osborne Reynolds built an apparatus to find a formula used by Engineers to protect the transition from laminar to turbulent flow This Modern version features a long tube with an inlet at the top where water enters water flows down the tube then exits from an outlet at the bottom at the top is the key piece this round vessel is filled with green dye this die is released through this nozzle which is very small compared to the diameter of the tube let's look at this small section of the device in operation a section just below the tip of the nozzle what you see here is the dye falling because of gravity the water is not flowing yet inside the tube I let water into the tube at a low flow rate and increase it slowly as the flow rate increases the flow looks the same while not very exciting it is an important observation by Reynolds as the flow rate increases keep your eye on the smooth flow of the dye and then boom the diet traces out the chaotic flow of water now turbulent flow the dye reveals that now the water violently spirals around with this experiment Reynolds highlighted the Key properties of the transition from laminar to turbulent flow to see that let's watch the flow change again as the flow rate increases first below a particular flow rate no turbulence occurs second that the transition occurs abruptly and third that there's an upper limit to the flow rate above which smooth flow cannot be sustained to understand this Behavior Reynolds compared the flow of water to a military troop if that troop stayed in formation that was to his mind like laminar flow if the troop became disordered soldiers going in every direction that mimic turbulent flow he reasoned that the orderliness of marching troops depends on three characteristics speed the number of soldiers in the troop and discipline a troop would struggle to stay in formation if it were fast-moving large or poorly disciplined although with discipline a faster large troop could stay in order the speed of the troop corresponds to the flow rate of the fluid and the size of the troop to the diameter of the pipe and the discipline is something called viscosity it's the resistance to flow see that compare water and honey the water flows readily while higher viscosity honey flows slowly Reynolds getted these three characteristics of fluid flow the diameter of the pipe the speed or better the velocity of the fluids flow and its viscosity into a single relationship the diameter times the velocity divided by the viscosity by using different size pipes changing the flow rate and using fluids with differing viscosities he observed that when this combination of variables was less than about 2100 some textbooks today say 2300 the flow was laminar and above that value the flow could become turbulent although by 4 000 the flow is turbulent with this relationship Engineers could know what to change to achieve laminar or turbulent flow for example if the flow were just at that transition value of 2100 and you wanted to be sure you had turbulent flow you could increase the pipe diameter so this ratio is above four thousand to ensure laminar flow decrease the pipe diameter to lower the ratio below 2100. you could also of course adjust the flow rate of the liquid or change to a liquid with a different viscosity and adjust the flow so it was laminar or turbulent this simple relationship among a few properties of a fluid inform the designs of Engineers for over a century I mentioned its application to flight but it's used throughout our engineered world to fully mix Pharmaceuticals Engineers design vessels that use turbulent flow to cool the strips of Steel fashion into every type of household metal object a laminar flow of other Cascades over the hot metal turbulent flow cools unevenly and induces defects and to conserve fuel baffles Channel The Air smoothly around a truck Reynolds approach a scientist might well complain doesn't describe turbulence at a molecular level this underlines the striking difference between science and engineering the scientific method strives to reveal truths about the universe while the engineering method seeks solutions to real-world problems we might though think that today's science would subsume all of engineering yet scientific breakthroughs never removed the need for engineering humankind developed the engineering method to reach Beyond codified scientific knowledge instead the advance of science only pushes out the boundary between the certain and uncertain and so resets the boundary where Engineers work this molecule illustrates that idea it's an enzyme in nature it enables a chemical reaction to happen our body is filled with thousands of enzymes that help our cells feed grow reproduce move and communicate with other cells this particular enzyme called subtilicin breaks down organic matter as shown here at the center of each petri dish is a lump of gelatin on the left it's covered in only water on the right this enzyme septalyzen is dissolved in the water in time lapse taken over nearly 30 hours note that the gelatin in the water remains intact but that in the enzyme it dissolves the enzyme septalyzen is a protein digesting enzyme it breaks the chemical bonds holding the gelatin together this ability to break bonds is of the utmost importance to Engineers braking and reforming bonds is what creates the engineered world around us in manufacturing chemicals paints Pharmaceuticals and Plastics and so it's no surprise that an engineer Francis Arnold decided to use these natural enzymes in industrial processes but here's the problem enzymes like sub to lysine work only in water and only under a narrow range of temperatures in the industrial uses envisioned by Arnold she needed it to work at all temperatures and in harsh solvents so of course when Arnold put it in organic solvent called dimethyl formamide think of paint stripper and you have a good idea of what this chemical is like the enzyme no longer digested proteins to engineer this enzyme Arnold Drew on a stunning scientific Advance a detailed molecular understanding of enzymes to illustrate that let's look at this section this Helix it's formed from 14 amino acids linked in a chain I'll go through them quickly here because the only things to notice are first that each of the amino acids is a simple molecule three or four carbon atoms with a few oxygens hydrogens or nitrogens attached second that we denote each type of amino acids with a single letter and third it's the order of these amino acids known as a sequence that determines the task performed by the enzyme seven different amino acids compose the sequence but the whole enzyme contains only 14 more 20 different types of amino acids in total so we could think of this unique enzyme as just the sequence of the amino acids that compose it some 275 amino acids the enzyme is one long chain all curled up and so this list this sequence shows the amino acids in order from the beginning of the molecule to the end we can see here the task that faced engineer Arnold this sequence of amino acids Works in water but which would she need to change to modify some devices so that worked in paint thinner would it be a single amino acid if so which one or maybe two of them needed to be changed she couldn't know because it's impossible to calculate from first principles the activity of a particular sequence of amino acids the choices she faced were astronomical 275 amino acids make up sub to license of which there are 20 different types so the number of possibilities is 20 raised to the 275th power a number far greater than the number of stars in the universe something estimated is 200 trillion to engineer some to license to work in harsh environments she used Nature's Own mechanism evolution here in essence is an illustration of what she did she randomly muted it naturally occurring sub to license she used a method which replaces an amino acid or two or three here and there I've Illustrated this here with just 10 mutations she set out 10 dishes filled with diluted paint thinner as I've called the solvent dissolved the mutated enzymes added a block of gelatin then wash the dishes for a day or two most of the mutated versions showed no ability to digest the gelatin but at least one managed to partially dissolve it she selected that enzyme created from it 10 more mutated versions filled the dishes with a stronger solution of paint thinner than tested again this time two showed Activity one of them more than the other she mutated that version 10 times filled the dishes with an even more concentrated solution of paint thinner then test it again until nature engineered for her an enzyme that worked in a harsh chemical environment almost as well as the original did in water in the decade sensor work enzymes engineered by this directed Evolution diagnose and treat disease reduce Farm waste improve textiles synthesize chemicals and pharmaceuticals and remove stains key ingredient of laundry detergents Arnold noted when accepting the Nobel Prize for chemistry that even today we struggle to explain how her revolved enzymes work a clear reminder that scientific advances don't remove uncertainty they simply move the borderline between certainty and uncertainty the perfect space for an engineer to work in the next video I explore the relationship of engineering to science I'm Bill hammock the engineer guy [Music] thank you [Music]

Channel: engineerguy

Views: 166,326

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Id: 9RAMqFg7laE

Length: 12min 22sec (742 seconds)

Published: Wed May 10 2023