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Old 12-25-2020, 09:48 AM   #71 (permalink)
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I think the issue is we cant test for that gaseous wetting, but places I worked with beryllium had you do a vacuum purge, sometimes.

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Old 12-29-2020, 11:19 AM   #72 (permalink)
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Jaguar

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Originally Posted by JulianEdgar View Post
Well, you're on your own.

I have already said how the head of Jaguar aero described flow attached through the action of downwash as 'attached flow', and today I noticed that the Aerodynamics of Road Vehicles (5th edition P 37) does the same. In describing the tuft pattern on the Adler (1930s?) the book says:

On both sides the vortices roll up, pull down the flow coming over the roof, and keep it attached until the lower end of the slant.

So you can either be big enough to admit your mistake and correct it, or you can do as you have always done in the past and just say that you're right and everyone else is wrong.
1) If that's the case, then It's my opinion that, the head of Jaguar aerodynamics has done a great injustice to the audience.
2) There's a REASON why the term 'downwash' exists.
3) There's a REASON why the term 'attached flow' exists.
4) To use the two interchangeably is a disservice to the aerodynamics community.
5) Providing his actual quote would help isolate and reveal any potential opportunity for mistranslation. In a trial, it would be submitted within the prosecution's brief, as evidence, during the discovery process.
6) The observation about the Adler does not validate your claim whatsoever.
7) The tufts orientation is fully explained within the context of separated flow phenomena, by default.
8) I've made no mistake. I know exactly what I'm looking at.
9) While I understand your experience, I also understand that your conclusion comes from a position of underinformed observation.
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Old 12-29-2020, 02:47 PM   #73 (permalink)
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Quote:
Originally Posted by aerohead View Post
1) If that's the case, then It's my opinion that, the head of Jaguar aerodynamics has done a great injustice to the audience.
2) There's a REASON why the term 'downwash' exists.
3) There's a REASON why the term 'attached flow' exists.
4) To use the two interchangeably is a disservice to the aerodynamics community.
5) Providing his actual quote would help isolate and reveal any potential opportunity for mistranslation. In a trial, it would be submitted within the prosecution's brief, as evidence, during the discovery process.
6) The observation about the Adler does not validate your claim whatsoever.
7) The tufts orientation is fully explained within the context of separated flow phenomena, by default.
8) I've made no mistake. I know exactly what I'm looking at.
9) While I understand your experience, I also understand that your conclusion comes from a position of underinformed observation.
It's not hard to understand. Attached flow is attached flow. Sometimes attached flow is caused by downwash.

As in Aerodynamics of Road Vehicles (5th edition P 37):

On both sides the vortices roll up, pull down the flow coming over the roof, and keep it attached until the lower end of the slant.

As in, what Adrian Gaylard wrote to me (the quote is in my book):

With an effective backlight angle approaching 30 degrees, itís often better to separate it as the drag can be lower for a fully separated rear flow, compared to one where rear pillar vortices are keeping the rear screen flow attached on a high screen angle.

Unfortunately this is yet another example where you make up your own definitions of words, and not follow what is in the technical literature.

And, once someone makes up their own definition of technical terms, it's not too many steps to then making up theories that revolve around those wrongly defined words.
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Old 12-29-2020, 03:23 PM   #74 (permalink)
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attached

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Originally Posted by JulianEdgar View Post
It's not hard to understand. Attached flow is attached flow. Sometimes attached flow is caused by downwash.

As in Aerodynamics of Road Vehicles (5th edition P 37):

On both sides the vortices roll up, pull down the flow coming over the roof, and keep it attached until the lower end of the slant.

As in, what Adrian Gaylard wrote to me (the quote is in my book):

With an effective backlight angle approaching 30 degrees, itís often better to separate it as the drag can be lower for a fully separated rear flow, compared to one where rear pillar vortices are keeping the rear screen flow attached on a high screen angle.

Unfortunately this is yet another example where you make up your own definitions of words, and not follow what is in the technical literature.

And, once someone makes up their own definition of technical terms, it's not too many steps to then making up theories that revolve around those wrongly defined words.
1) 'downwash' flow is downwash flow.
2) Sure, the tufts are oriented as if they were is a more favorable pressure regime, streamlines were diverging, pressure building, base pressure increasing, drag reducing.
3) That's not happening at all.
4) You have a small wake of extremely low pressure, plus concomitant attached vortex drag of the highest order, high lift, and overall higher drag, compared to a streamlined aft-body.
5) At 30-degrees you're entering bistable flow, of the highest imaginable drag known, so in that respect either a more stable, fastback or squareback wake in desirable. Either one is better.
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Old 12-29-2020, 03:27 PM   #75 (permalink)
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Quote:
Originally Posted by aerohead View Post
1) 'downwash' flow is downwash flow.
2) Sure, the tufts are oriented as if they were is a more favorable pressure regime, streamlines were diverging, pressure building, base pressure increasing, drag reducing.
3) That's not happening at all.
4) You have a small wake of extremely low pressure, plus concomitant attached vortex drag of the highest order, high lift, and overall higher drag, compared to a streamlined aft-body.
5) At 30-degrees you're entering bistable flow, of the highest imaginable drag known, so in that respect either a more stable, fastback or squareback wake in desirable. Either one is better.
You didn't address any of the points that were made.

No technical reference or specialist has a definition of attached flow that excludes attached flow being caused by downwash.

You've made up your own definition of the term. That's very odd.
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Old 12-29-2020, 04:22 PM   #76 (permalink)
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you've

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Originally Posted by JulianEdgar View Post
You didn't address any of the points that were made.

No technical reference or specialist has a definition of attached flow that excludes attached flow being caused by downwash.

You've made up your own definition of the term. That's very odd.
There was never any confusion between the two until you and your select panel of experts ( emetic ) surfaced.
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Old 12-29-2020, 04:31 PM   #77 (permalink)
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Quote:
Originally Posted by aerohead View Post
There was never any confusion between the two until you and your select panel of experts ( emetic ) surfaced.
Back to that abuse again...

No formal reference, no tech paper and no expert I've ever found supports your definition of attached flow excluding attachment caused by downwash.

A great example of where Aerohead believes he is right and everyone else is wrong.

The significance is, of course, that this error then leads to further errors and erroneous theories.
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Old 12-29-2020, 05:00 PM   #78 (permalink)
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Hucho

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Originally Posted by JulianEdgar View Post
Back to that abuse again...

No formal reference, no tech paper and no expert I've ever found supports your definition of attached flow excluding attachment caused by downwash.

A great example of where Aerohead believes he is right and everyone else is wrong.

The significance is, of course, that this error then leads to further errors and erroneous theories.
Hucho dispelled everything you've advocated, however, for some reason you came away from the book without comprehending it.
It has nothing to do with me, and everything to do with fluid mechanics.
From my perspective it's as if comments are specifically designed to appear so inflammatorily ignorant, they are guaranteed to impel only a strongly emotional response from the recipient, which can then be employed as ammunition to paint a character flaw upon the respondent by the commentator, as the sole aim. This is my experience.
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Aerodynamics for us is about profile drag.
Profile drag is about pressure drag.
Pressure drag is about separation.
Control the separation and you win all the marbles.
And if it's about profile drag, then it's about profiles which create it, or not.
That's where the dimensional analytics come in. They're a road map, just like Hucho said, in between the lines.
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Old 12-29-2020, 05:32 PM   #79 (permalink)
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Quote:
Originally Posted by aerohead View Post
That's where the dimensional analytics come in. They're a road map, just like Hucho said, in between the lines.
Yep, according to you, it's such a critically important thing and it was just written "between the lines"!

How extraordinary. You'd think there'd be chapter after chapter on it wouldn't you?

Dimensional analytics. Sounds so much better than "make guesses from a template".

(And which template? There are five, all with quite different shapes. Gosh, this could get really confusing. Just as well it's not real, isn't it?)
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Old 12-29-2020, 05:54 PM   #80 (permalink)
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between the lines

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Originally Posted by JulianEdgar View Post
Yep, according to you, it's such a critically important thing and it was just written "between the lines"!

How extraordinary. You'd think there'd be chapter after chapter on it wouldn't you?

Dimensional analytics. Sounds so much better than "make guesses from a template".

(And which template? There are five, all with quite different shapes. Gosh, this could get really confusing. Just as well it's not real, isn't it?)
Yes, which brings us back to perspicacity.
Every element of the 'template' is spelled out by Hucho in a constellation of dots.
He provides the premise.
He provides the image.
He provides the empirically-derived quanta.
There is only one which embodies the drag minimum, in the context of an actual vehicle that a driver could see out of.
He explains the application.
We're talking about a 'basic' body, not a 'complex' body.
They're real alright.
And the future, if we want really low drag.

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