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The Obsidian File - Mono Wheel Fairing

 
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Area-51



Joined: 03 May 2021
Posts: 391

PostPosted: Wed Apr 12, 2023 4:34 pm    Post subject: The Obsidian File - Mono Wheel Fairing Reply with quote

The second black op Obsidian File has been sanctioned for declassification... Techniques rumored used for original data extraction have been dispelled, however some information remains redacted... Some names have been changed to protect operatives still active within current high level field ops.

A quick review of data within this file focuses upon debated myth and legend of the Europa Mono wheel fairing... preliminary assessment of the facts shrouding this vicarious circle of assumptions points towards the successful mitigation of noise and turbulence; however the studies reviewed so far are just loose preliminary tasks used to verify test field integrity.

The attached images show Acoustic Power "noise levels", and the first image Velocity "air movement" at 51m/sec... higher resolution and more solution solving iterations will provide more clarity toward actuals; but what has been revealed so far is useful and indicative toward a standard equipped mono.

Acoustic power under 50db is equivalent to sitting in a open park on a mild day... 70db starts to become noticeable... 80db is audible... 90db is noticeable... 100db is loud... 105db is fricken loud...


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Area-51



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PostPosted: Thu Apr 13, 2023 1:14 am    Post subject: Re: The Obsidian File - Mono Wheel Fairing Reply with quote

Today was spent raising the resolution of the analysis and re-running the preliminary solution... Some points of interest were glanced over also, being static pressure inside the engine cowl, flow velocity through various airframe vents and openings...

Regarding the main gear area... as the images show, with the gear retracted and set at its operational position, due to the existing lower cowl faring, it remains just on the cusp of free-stream air during flight; however, about 80db of noise is being displayed downstream; whether this is caused by the wheel or the cowl faring is not yet determined... some updated images attached; the first Velocity, the next two Acoustic Noise.

The areas responsible where most noise is generated are the flap tube ports in the fuselage; somewhere in the order of 90db. However this may alter with the wings installed.

Engine cowl interior is experiencing a positive rise in atmospheric pressure; so potential air flow through heat exchangers will be reduced. Some European's have enlarged cowl exit vents to allow more air to exit increasing flow through heat exchanges.

Velocity of air flowing through the cabin is approximately 12-15m/sec at 100kt airspeed. Volume flow has not yet been determined.

Next session will be looking at same results while utilising a wheel faring and comparing the affects.


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Area-51



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PostPosted: Sun Apr 23, 2023 4:50 am    Post subject: Re: The Obsidian File - Mono Wheel Fairing Reply with quote

The past weekend has not been good for flying; so more numbers were crunched and more fairings were assessed; it was interesting to try some known shapes, no shapes, different retraction heights, and an initial design developed way back near the beginning of all this.

As usual the control piece was the standard mono in standard flight configuration at 100kt velocity (51m/sec). The airframe was stripped back to fuselage only to reduce computer power and solving time. Several indicators were implemented, Drag, Lift, Surface Velocity, Surface Acoustic Power... Fairings were tried as semi and fully enclosed scenarios.

What the computer said...

The standard mono wheel, when retracted, skips on its tyre upon free stream air; most all the remaining tyre remains within a protected pocket created by the lower cowl deflector covering the muffler... employing a fairing does little to reduce drag, however it does reduce acoustic noise within the undercarriage well... a fully sealed fairing reduces this acoustic noise to near zero... the variance upon drag factor between no fairing and fully enclosed is about 1kg out of 38kg total; Lift variance is 1.8kg less with a fairing out of 7.8kg total and is probably due to the tyre skipping on the free stream air... and there's not a great more to add for the mono wheel faring other than the ball ended enclosed shape providing the best aerodynamic results.

The idea of a fairing around the main gear looks and sounds great and appears to not offer much else for the "you beaut go faster" europa addict.

The best bang for buck might be to simply retract the gear a couple of inches further...

And thats about it on this one; myth busted 🤷🏼‍♂️

Attached images relate to velocity and acoustic comparisons.

NOTES:

Acoustic Power Levels (db)
105 - Red
90 - Orange
75 - Yellow
55 - Green
25 - Light Blue
0 - Dark Blue

Velocity (m/sec)
125 - Red
90 - Yellow
51 - Green
35 - Light Blue
8 - Dark Blue


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Last edited by Area-51 on Sun Apr 23, 2023 5:22 am; edited 1 time in total
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peterz(at)zutrasoft.com
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PostPosted: Sun Apr 23, 2023 5:17 am    Post subject: The Obsidian File - Mono Wheel Fairing Reply with quote

Different from noise, i notice significant (and irritating to me lol) buffeting starting at 120knots and increasing slightly as speed increases.

Intuitively, buffeting energy would be draggy with the pressure waves traveling outward from the tunnel….

PeteZ

Quote:
On Apr 23, 2023, at 8:56 AM, Area-51 <goldsteinindustrial(at)gmail.com> wrote:



The past weekend has not been good for flying; so more numbers were crunched and more fairings were assessed; it was interesting to try some known shapes, no shapes, different retraction heights, and an initial design developed way back near the beginning of all this.

As usual the control piece was the standard mono in standard flight configuration at 100kt velocity (51m/sec). The airframe was stripped back to fuselage only to reduce computer power and solving time. Several indicators were implemented, Drag, Lift, Surface Velocity, Surface Acoustic Power... Fairings were tried as semi and fully enclosed scenarios.

What the computer said...

The standard mono wheel, when retracted, skips on its tyre upon free stream air; most all the remaining tyre remains within a protected pocket created by the lower cowl deflector covering the muffler... employing a fairing does little to reduce drag, however it does reduce acoustic noise within the undercarriage well... a fully sealed fairing reduces this acoustic noise to near zero... the variance upon drag factor between no fairing and fully enclosed is about 1kg out of 38kg total; Lift variance is 1.8kg less with a fairing out of 7.8kg total and is probably due to the tyre skipping on the free stream air... and thats about it for the mono wheel faring with the ball ended enclosed shape providing the best aerodynamic results.

Myth Busted...

Attached images relate to velocity and acoustic comparisons.




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Area-51



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PostPosted: Sun Apr 23, 2023 5:25 am    Post subject: Re: The Obsidian File - Mono Wheel Fairing Reply with quote

Interesting... probably worth increasing the velocity parameters to 75m/sec and see what happens 🤷🏼‍♂️

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budyerly@msn.com



Joined: 05 Oct 2019
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Location: Florida USA

PostPosted: Sun Apr 23, 2023 8:15 am    Post subject: The Obsidian File - Mono Wheel Fairing Reply with quote

Consider also the gap between the frame/wheel and fuselage opening. That gap has to be cut "like Goldilocks" or just right or air swirls around and gushes up into the well.



NACA had tests on the partially retracted gear and frankly, a half-buried tire is a good compromise. Drag was decreased slightly in the wind tunnel with a narrower gap. In these tests the gap was closed up to the tire and the tire gap was as small as practical. Photos are grainy and virtually impossible to find from NASA. Heinkel did work in this area also.

Most 1930-40s aircraft with partially exposed wheels did hide the wheels in the nacelles or made covers for the gap in the wings back to the tire to clean up the gap and reduce drag. Making a flange with rounded edge in the rear of the wheel well area was also done to clean up the exit and prevent air pressure buildup in the well. ( As done by Seversky in the P-35) Douglass put the oil cooler on the C-47 just before the tire to cut the drag. Crude but effective. Bellanca did no streamlining until the Viking series. Adding a small cover to the front helped, so they made a complete door to enclose the gear. A full fairing is nice, but the extra weight and complexity becomes tedious to complete effectively. Many folks up north simply removed the rear door.

See NACA Report 518 for some drag numbers (very crude stuff, drag is in pounds, but the tire size is familiar looking) to bounce off your calcs.

Enjoy your computer work. Im doing 3D printing stuff and cooling airflow and enclosure mods using similar programs. The learning curve was and still is steep. Too many assumptions have to be made to compromise on airflow and pressure build up. Yuck. It is a hit and miss (for me anyway) on getting the best airflow bang for the buck and time.

Best Regards,
Bud Yerly


From: owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com) <owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com)> on behalf of Area-51 <goldsteinindustrial(at)gmail.com (goldsteinindustrial(at)gmail.com)>
Sent: Sunday, April 23, 2023 9:25:27 AM
To: europa-list(at)matronics.com (europa-list(at)matronics.com) <europa-list(at)matronics.com (europa-list(at)matronics.com)>
Subject: Re: The Obsidian File - Mono Wheel Fairing



--> Europa-List message posted by: "Area-51" <goldsteinindustrial(at)gmail.com (goldsteinindustrial(at)gmail.com)>

Interesting... probably worth increasing the velocity parameters to 75m/sec and see what happens 🤷♂




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Area-51



Joined: 03 May 2021
Posts: 391

PostPosted: Sun Apr 23, 2023 2:26 pm    Post subject: Re: The Obsidian File - Mono Wheel Fairing Reply with quote

Thanks for the input there Bud; always thought provoking..

Gaps and edges can be noise generators. The semi enclosed fairing has a large gap at the rear to allow tyre passing. On something like the europa installing bristle brushes at the gaps might offer an affective cheap and light solution here.

Cooling ducts on 3D printers are a real challenge. I did one a few years back as i wasnt happy with the factory side flow versions; so i designed up a really affective single head unit which resulted in a 150g lighter print head; took five assumptions to get the flow balance correct between the print nozzle and heat break; there is an internal splitter used... works great! Let me know if you are interested, can send you the STL file, ready to print.

The black version was a Makerbot styled ripoff and a total fail; the grey one on the left is a winner.


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PostPosted: Sun Apr 23, 2023 5:39 pm    Post subject: Re: The Obsidian File - Mono Wheel Fairing Reply with quote

Breakfast today has turned into brunch as all three model variations had a higher velocity of 75m/sec (150kt) applied; and revealed an interesting anomaly.

Its not certain or being ruled out that at the higher air speed an acoustic pressure wave is detected traveling rearward along the fuselage belly aft of the main gear. (the fully enclosed fairing does not exhibit this trait).

Other results on the acoustic aspect shows db levels increasing some 50%; the loudest areas being where deflected free stream air at the lower engine cowl fairing rejoins slower moving air exiting the engine bay area; some 105db; quite audible over everything... installing a trailing fence may reduce this turbulent corridor.

The pressure wave though is interesting, at 70-80db it would be noticeable and the cause of it would likely be related to the flutter of turbulence created by air passing over and behind the cylindrical shape of the tyre. As Bud mentions above there is also the added element of air escaping the gaps of the fairing and exposed main gear rejoining faster moving air... The belly of the fuselage is quite flexible and is likely oscillating enough to cause annoying pressure pulses within the cockpit.

Employing fairing fences at the lower engine cowl and raising main wheel higher into the well might provide an answer to the above situation. (Raising the main wheel higher did not provide any relief).

Regarding Drag and Lift comparatives at 150kt, standard and semi enclosed setups were identical in Drag with the later giving up 3.0kg of Lift; again the tyre is removed from the free stream... The fully enclosed setup provides some 3.0kg Drag reduction and gives up 2.0kg of Lift.


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Area-51



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PostPosted: Sun Apr 23, 2023 8:08 pm    Post subject: Re: The Obsidian File - Mono Wheel Fairing Reply with quote

Brunch has turned into lunch..

The fence concept has provided value by reducing the previous acoustic pressure pulses to almost zero and assisting in keeping trailing turbulence tighter within the fuselage centerline (much like driving an old convertible with the side curtains on; pleasant)... Drag and Lift gains and losses were not anything worth noting; mostly "shut that noise up" stuff on this one (105db sources reduced to 75db); advantages being greatest using the semi enclosed fairing option, however both semi enclosed and standard setups nullified the trailing pressure pulse effects displayed at 150kt... the fully enclosed setup showed similar db reductions along with reduced surface velocity however an alternate fence would perform better toward db reduction... two thumbs up on this one; an easy peazy Mod...


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Velocity Semi Enclosed Without Fence
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peterz(at)zutrasoft.com
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PostPosted: Mon Apr 24, 2023 12:56 am    Post subject: The Obsidian File - Mono Wheel Fairing Reply with quote

Fence details?

Quote:
On Apr 24, 2023, at 12:15 AM, Area-51 <goldsteinindustrial(at)gmail.com> wrote:



Brunch has turned into lunch..

The fence concept has provided value by reducing the acoustic pressure pulses to almost zero and assisting in keeping trailing turbulence tighter within the fuselage centerline... Drag and Lift gains and losses were not anything worth noting; mostly "shut that noise up"; advantages being greatest using the semi enclosed fairing option, however both semi enclosed and standard setups nullified the trailing pressure pulse effects... two thumbs up on this one.




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=510684#510684











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Area-51



Joined: 03 May 2021
Posts: 391

PostPosted: Mon Apr 24, 2023 2:07 am    Post subject: Re: The Obsidian File - Mono Wheel Fairing Reply with quote

Lunch has now turned into dinner.. there was a brief hiatus in the weather where the sun came out and a bunch of bananas were lopped from the tree and many hands cut off; of bananas, not apes...

So just for entertainment and curiosity the fence concept was extended further to a more aft limit near to the fuel drains... that worked favourably for all three options; so the concept was developed into an undeveloped triangular rib concept extending to around 1m short of the stern. And that appears to also work favourably toward keeping air flowing neatly and quietly downstream to the undercarriage. A secondary affect if shaped with foam and glassed over would be added rigidity of the belly skin and less tendency for panel drumming. The fully enclosed option begins to deteriorate in aerodynamic performance as its shape is no longer optimised for the altered environment.

Peter the fence is just a 3.00mm piece of flat plate running from the lower engine cowl side face rearward; a block of triangular shaped foam glued to the skin would also work for a temporary trial... ending it just forward of the fuel drain vents will function well; the fence height used in tests is 64.0mm and falls off to 15.0mm height at the rear.


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754EDD4F-88A1-43DC-BE1C-C456FB1619AC.jpeg
 Description:
Acoustic Rib Semi Enclosed
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Velocity Rib Standard
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Velocity Rib Semi Enclosed
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 Description:
Fence 1st Version
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Acoustic Rib Standard
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clivesutton



Joined: 23 Jan 2013
Posts: 187
Location: KENILWORTH

PostPosted: Tue May 09, 2023 11:13 am    Post subject: Re: The Obsidian File - Mono Wheel Fairing Reply with quote

Area-51, i follow your posts with great interest - thanks for posting all this in images we can all visualise.

A question that you might know some answers to: do you have any drag data that relates to EACH of the individual speed kit fairings, please?

The reason i ask is that i took the view when fitting my Mono speed kit fairings, that the inboard and mid-flap brackets would not benefit from fairings - on the basis that they would increase frontal area whereas the brackets as they stand are just 'blades' in the airflow. I fitted the outrigger bracket fairings though.

But i have no data to substantiate that action - just a gut feel.

I would be most grateful for your view - and if you have the time/interest, it would be useful if we could see the effectiveness of each of the factory fairings for each type as well . . .??


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