The love of turbulence.

[Garfly]

Yes, life is like golfballs, full of depressions; but also like VGs, full of turbulence.

 

(Warning: this content may only be comprehensible to OME and the other physicists among us.  ;- )

 

 

 

[Jabiru7252]

Remember learning this back when I did air and water balancing. Turbulent flow in airconditioning ducts could not only cause damage over time, but cause low frequency oscillations that drove people bonkers. 

[Yenn]

I didn't watch much of the video, not being a phissysist, but it did remind me about the quickest way to empty a bottle of liquid.

[old man emu]

3 hours ago, Garfly said:

Warning: this content may only be comprehensible to OME and the other physicists among us

No formulas. No Algebra. No Calculus. 

 

The video can be watched and understood by anyone with a grasp of conversational English. I think the hardest concept to understand was "laminar flow", but that was explained in simple terms near the beginning of the video.

 

What did I learn from it? I learned what a Reynold's number meant. I learned that a washed plane is a fast plane. It also reminded me that what a homebuilder does to create teh surface of wings will greatly affect aircraft response to airflow. 

 

Included in the video is an explanation of how vortex generators work to improve performance and control authority at low airspeeds and high angles of attack. For more on that go to this site:  https://microaero.com/

 

I also learned that if you want your balls to go further, keep them rough.

[IBob]

I enjoyed that. And some beaut images too!

What I still don't really get is the stuff about VGs (and gold balls). Not that I doubt they work in altering wing behaviour and flight of ball, but when it gets to the bit where they describe just how that happens, the explanations always seem to me to be vague:

 

In the case of the golf ball, while the downstream turbulance appeared different, the laminar flow didn't appear to be sticking any better to the ball.

 

In the case of the VGs, you're making a vortex which swirls or rolls the laminar air. Okay, fine, I got that. But why does that then delay the onset of stall???

[old man emu]

Laminar flow around golf ball. Either my eyes are better than yours, or my monitor is. I watched the video on full screen and I could in fact see a longer space behind the ball before the eddies appeared.

 

Vortex Generators. The impression I got from the images was that without VGs, at the stall, the airflow separated from the surface of the wing and never returns. With the VGs it still separates, but swirls back down to contact the wing closer to the trailing edge. That return to the surface must result in enough lift to reduce stall speed. 

 

[skippydiesel]

1 hour ago, IBob said:

I

 

I But why does that then delay the onset of stall???

This numskull recons that it induces mixing of the fast air (molecules ?) with the slowing air close to the surface, which induces an acceleration, which helps to "stick" the airflow to the surface of the wing for longer (not for ever) enabling a lower stall speed a - slower controlled flight, shorter take offs, steeper climb outs - am I close??????

[old man emu]

2 minutes ago, skippydiesel said:

am I close

One post too late. Missed by thaaat much!

[Jabiru7252]

It's all magic folks. Don't need to know this stuff to be a good pilot. Just the basics will do.

[skippydiesel]

10 minutes ago, Jabiru7252 said:

It's all magic folks. Don't need to know this stuff to be a good pilot. Just the basics will do.

True to a point Jab however it doesnt hurt to have a little theory in your life. Even if you and I cant expect or want to reach the hight of understanding of OME , RFguy or Facthunter (& many others) it will help make you a better pilot.

[Jabiru7252]

I'm immeasurably clever (mum had me tested) and find physics etc. no great challenge.  I did work for twenty years in a physics environment. It's just that some poor sod may think they are dumb for not knowing the deep stuff when in fact it's not even in the BAK syllabus. (I'll assume you did BAK for GA license). As a pilot just knowing what form drag, parasitic drag and being drag is all that's really needed. I do learn heaps reading the posts on this forum. 

[old man emu]

1 hour ago, Jabiru7252 said:

It's all magic folks. Don't need to know this stuff to be a good pilot. Just the basics will do.

You are not wrong. It's just that this place is a good one to discuss the minutiae of aviation. Just as it's a good place to discuss famous or rare aircraft and all the other stuff we discuss. You learn stuff all the time. It maybe pushed to the back of your memory, but one day it will be needed to impress onlookers, or to destroy a Richard Cranium. 

[skippydiesel]

At the risk of going off on a tangent:

 

I would liken having some basic understanding of your vehicle/equipment (air or ground) to driving a car or operating machinery. Its absolutist true that you can teach someone to function behind the wheel , without having any mechanical knowledge (especially these days)but I would not really call them drivers.

 

So many people cant even check tyres pressures/oil/coolant/windscreen wash - so what hope have they of being aware of their vehicles degraded performance/safety due to low tyre pressure, defective shocks, loose steering linkage, etc etc. Some basic understanding might just save their lives and others. In addition, basic understanding will reduce operating cost, maintain the value of your asset and optimise its service life.

 

If using industrial/agricultural equipment; I differentiate between drivers & operators  - the latter having some deeper understanding of the machinery and the standard of work desired. You can only be an operator if you are "simpatico" with your machine and know what standard of work is to be achieved and how to configure it accordingly - basic understanding. 

 

So yes you might learn to manipulate the controls of an aircraft so that it can fly & land with some degree of repeatability but without some degree of basic knowledge, will you be alarmed by an increasing oil consumption, a floppy control surface, a strange noise at certain engine rpm, a low tyre pressure, a wrinkled wing skin, drag on a control rod, etc etc ???

 

Of course basic undertaking, gives no assurance that the pilot will take notice and could lead him/her to a degree of overconfidence - stupidity, ego, "she'll be right mate" is part of the human condition, that no amount of knowledge seems to completely eradicate.

[rgmwa]

14 hours ago, Jabiru7252 said:

I'm immeasurably clever (mum had me tested) ....

Which end of the scale?

[Jabiru7252]

She didn't say 😞

[facthunter]

When the air flows over a wing at an angle to the relative airflow there's a point where separation commences. IF you blow that area or impose vortices on it t he separation will take place further along  the wings chord and more lift is produced at those angles since the area "working" has been increased. Nev

[CT9000]

On 07/02/2021 at 10:09 AM, skippydiesel said:

At the risk of going off on a tangent:

 

I would liken having some basic understanding of your vehicle/equipment (air or ground) to driving a car or operating machinery. Its absolutist true that you can teach someone to function behind the wheel , without having any mechanical knowledge (especially these days)but I would not really call them drivers.

 

So many people cant even check tyres pressures/oil/coolant/windscreen wash - so what hope have they of being aware of their vehicles degraded performance/safety due to low tyre pressure, defective shocks, loose steering linkage, etc etc. Some basic understanding might just save their lives and others. In addition, basic understanding will reduce operating cost, maintain the value of your asset and optimise its service life.

 

If using industrial/agricultural equipment; I differentiate between drivers & operators  - the latter having some deeper understanding of the machinery and the standard of work desired. You can only be an operator if you are "simpatico" with your machine and know what standard of work is to be achieved and how to configure it accordingly - basic understanding. 

 

So yes you might learn to manipulate the controls of an aircraft so that it can fly & land with some degree of repeatability but without some degree of basic knowledge, will you be alarmed by an increasing oil consumption, a floppy control surface, a strange noise at certain engine rpm, a low tyre pressure, a wrinkled wing skin, drag on a control rod, etc etc ???

 

Of course basic undertaking, gives no assurance that the pilot will take notice and could lead him/her to a degree of overconfidence - stupidity, ego, "she'll be right mate" is part of the human condition, that no amount of knowledge seems to completely eradicate.

Thanks for the tangent, learning driving from an early stage seems to make the difference between steerers and drivers and this empathy with machinery also follows for aircraft boats trucks and any thing else that requires a "big picture" situational awareness. I may get slammed for admitting this but my grandkids had a ball last week doing their version of synchronized dancing on my runway with the Bobcat and Zero turn mower and they are primary school kids. The point being that they grow up operating machinery have empathy and control comes naturally. My 12 yo grand daughter is very safe operating my backhoe and next month will by introduced to riding a motorbike. Properly supervised they learn and safety becomes second nature over time.

[Jabiru7252]

I had a friend who couldn't do better than grade seven math and English but he could thread a needle with a backhoe...

[old man emu]

10 hours ago, CT9000 said:

Properly supervised they learn and safety becomes second nature over time.

It's the supervision that instils safety.

 

Nearly every day I hear cars and motorcycles roaring along my residential street (50 kph zone). Engines are revved to peak RPM and gear changes are done rapidly. Why? Because the operators spent too much time playing Grand Theft Auto and have come to expect the fast and furious is so macho. I'm appalled at the number of "burnout" marks on residential streets. Clearly, those who make them have absolutely no idea why a burnout has a purpose in only one type of motor sport. I cringe when I thing of the damage they are doing to the transmission systems of their cars. It's a wonder that we don't see more of them flipping their cars because the front driveshaft universal gives way and drops the shaft onto the road. 

 

The poor standard of vehicle operation in a traffic environment throughout the whole population is deplorable. I see poor road positioning; poor sight distance management, and poor planning and review displayed every time I venture out on the roads. I pray to the Lord to ease the burden St Christopher bears in ensuring the safe travel of these incompetent drivers.

[onetrack]

It's a veritable minefield, teaching, and letting young kids drive equipment and vehicles. You need to understand a childs level of reasoning ability for their age, and whether they can react correctly in the case of any emergency.

I have way too many stories to tell you of children killed in farming accidents with machinery. They do not have the knowledge, the strength. the experience, or understanding of dangers.

 

They're constant risk-takers, because childhood is all about exploring limits. A childs life is all about fun. Responsibility is something that adults have to deal with - they don't. 

 

There are around 300 children killed just in farming accidents in America alone every year - and the number in Australia is still a sobering number. The vast majority of these deaths are totally preventable - usually because the child was operating a machine that was way beyond their ability to understand where the full range of dangers lay with it.

 

I well remember one bloke telling me of visiting a farm where a 7 yr old was allowed to ride a 600cc quad bike. He killed himself - very quickly - because a 600cc quad bike is a beast, even in the hands of an adult.

 

This bloke said the pall of gloom that hung over this farm was omniprescent. The family ended up selling the farm, they couldn't cope with seeing the site where their beloved child killed himself, because they lacked the foresight to understand a childs development and abilities.

We have a lower age limit for allowing children behind the wheel of road-going vehicles. There are many very good reasons for that - and even a lot of 17 yr olds still don't have enough maturity and responsibility to handle a vehicle.

I personally believe about 14, is the right age to start teaching children how to operate machines and vehicles. But even then, with intensive supervision and good training.

 

We ceased employing children in coal mines and textile mills for good reason, over 100 yrs ago. Yes, a lot was to do with the way they were treated, but the death toll amongst the children working with machinery in that era was horrendous.

 

Edited February 14, 2021 by onetrack

[old man emu]

I recently learned that a child under 12 thinks in terms of what can be sensed. It is only after that age that they can begin to think in abstract terms. So there is no point in expecting a Primary school kid to fully understand responsibility. If you want to see  this lack of grasp of abstract thinking, stand outside a primary school at 3:00 pm. Your heart will be in your mouth. 

[CT9000]

Onetrack with the greatest of respect please do not take things out of context. I would never send the grandkids off to do their own thing. They are closely supervised at all times. If you read between the lines I mentioned she is 12 yo. and about to learn to ride a motorbike in other words when she is ready to learn and that also means accept the associated responsibilities that go with this learning. If some one sends a 7yo out on a 600cc quad that is just stupid. A part of the reason that a 17 yo has a problem with handling a vehicle is as you say the fact that immaturity is a problem and it is also a "dog let off a chain" problem. If you grow up using machinery of whatever  sort under supervision it becomes second nature to respect the dangers and limitations of that equipment. It is the job of the trainer to introduce the new skills as the student is ready to absorb the new learning. I believe that the age is not the determinate factor when it comes to teaching anything but when someone is ready to learn they can be taught. I would never suggest that you let kids loose to "run their own race" but in the right environment when a child is ready they can be taught under supervision to learn new skills and that also involves driving. At 12 yo my son could back a truck and trailer combination he is now in his forties and still has his first car which has a modified v8 never had a at fault collision does not get traffic tickets in other words is a model citizen but exposed to machinery at an early age. Ok I will get off my soap box now.       

[onetrack]

I'll say it more clearly. You can't put an old head on young shoulders. No matter when you think you've imparted to them all they need to know, an event will crop up which is beyond their experience to handle, and disaster is sure to follow.

I've driven all types of machinery for 55 years, I started at 16, and I'm a qualified operator trainer. I have had plenty of narrow escapes personally from disaster - many of them not of my making - and even in my 30's, I was still learning.

One of the basic problems with putting children in charge of powerful machines is that they can often barely see through the screen, or reach all the pedals and controls properly. All it takes is one slip. Remember Rudyard Kiplings "The Secret of the Machines".

All powerful machines are designed specifically for adult-sized bodies, weights, and head positioning. Then there's the problem that many farmers are poorly trained, and take a great deal of unnecessary risks - and they pass this onto their children with their deficient training techniques.

 

The idiot in the story below lost his 8 yr old daughter, because he believes 8 yr olds should have the right to drive "junior dragsters". Even after losing her, he still thinks it was a "1-in-a-million" accident. No it wasn't, it was an accident waiting to happen, and it's simply stupidity in his level of thinking and understanding. You could give this as an example of Darwin at work, I guess.

 

https://www.abc.net.au/news/2017-11-13/junior-drag-racing-suspended-after-anita-board-crash/9144166

 

Edited February 14, 2021 by onetrack

[old man emu]

8 hours ago, onetrack said:

The idiot in the story below lost his 8 yr old daughter, because he believes 8 yr olds should have the right to drive "junior dragsters"

What was not reported in that story was the result of the investigation into the causes of the accident. Obviously because the story came out before the investigation was completed. We, as readers, don't know what the sequence of events was. Obviously there was a loss of control, but there are many things that can lead to that - the vehicle, the environment, or the driver. Perhaps the cause will be found to be the failure of a widget. That's a one-in-a-million. 

 

Whatever the cause of that incident was, zeroing in on it detracts from the general propositions we are discussing. As Onetrack said, "All powerful machines are designed specifically for adult-sized bodies, weights, and head positioning"  More specifically, transport machines are design for the target user. Go stand outside a primary school one afternoon and see how dangerous kids on bikes and scooters are to themselves and others. Even those on foot are prone to running into the paths of others in their haste to move.

 

 

[Garfly]