Aero question

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Flanker27
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Joined: Fri Jan 28, 2011 10:29 am

Aero question

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A question for aero guys...

Image

wich of these spoilers is the best to reduce drag (and maybe give downforce) ?

p.s. please do not blame me for the car :) , i also own something "better" (MX-5 RF with 160hp, limited slip differential, Recaro seats, etc.) but i love my old k11

NL_Fer
NL_Fer
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Joined: Sun Jun 15, 2014 8:48 am

Re: Aero question

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My Seat Leon has one fitted for drag reduction. Looks most like type 1

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Flanker27
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Joined: Fri Jan 28, 2011 10:29 am

Re: Aero question

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Yes, all hatchback cars of today have a little rear spoiler, and sometimes it expands on the sides... look for example tha last VW Golf , on the side of the rear window there is a black spoiler

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Big Tea
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Re: Aero question

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Flanker27 wrote:
Fri Nov 09, 2018 9:08 pm
Yes, all hatchback cars of today have a little rear spoiler, and sometimes it expands on the sides... look for example tha last VW Golf , on the side of the rear window there is a black spoiler
I thought they were to keep the back window clear?

Not a wind up, seriously. We had a micra without and one of the later with (as in type 1 white) and the window was much better.
Possibly just a by product
One test is worth a thousand expert opinions

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strad
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Re: Aero question

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I thought they were to keep the back window clear
Correct. Most of the newer square back vehicles incorporate a lip to break the vacuum behind which sucks up dirt and dust onto the rear window. As a byproduct it cuts drag slightly imo.
To achieve anything, you must be prepared to dabble on the boundary of disaster.”
Sir Stirling Moss

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Vyssion
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Re: Aero question

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Flanker27 wrote:
Mon Oct 29, 2018 4:26 pm
A question for aero guys...

Image

wich of these spoilers is the best to reduce drag (and maybe give downforce) ?

p.s. please do not blame me for the car :) , i also own something "better" (MX-5 RF with 160hp, limited slip differential, Recaro seats, etc.) but i love my old k11
I had a small section of one of my dissertations which looked into this kinda. Please do excuse my young and "green" aerodynamic analysis :lol: Hopefully the picture gives you a sense of whats going on regardless.


The second part of the 3-Dimensional simulations conducted with the full Golf Mk1 Model, were a location sensitivity. The idea behind these was to test positions of the rear wing above the roof line close to the forward side of the backlight region and another to the rear area, one position with the aerofoils leading edge in line with the roof plane, and one more with the aerofoil below it (Shown below in Figure 93). As was previously found with the varying angle of attack tests, there was full attachment of the flow for 11.5° and still partial attachment for 22°. For this reason, all of these locations were to be tested at both of these angles to investigate whether a warping or twisting of the element would be different within a particular region should they perform better than the original location.

Figure 94 shown above has been included to give a sense of the air flows behaviour for each of the combinations tested. Firstly, it is clear that when the wing assembly was located in its original position, that the wake vorticity of the Golf was drawn upwards into that of the aerofoils. As the wing is able to generate a large suction peak on the surface nearest to this region, this behaviour is to be expected and may be why the aerofoil performs so well at incident angles which most other aerofoils would fully stall at. Moving the aerofoil rearwards but keeping it above the roof panel changed the direction of the wake for the 11.5° aerofoil with its flow being largely unchanged, however, in the 22° image, a clear leading edge stall has eventuated due to the wakes suction peak greatly overcoming the boundary layers resistance to an already substantial adverse pressure gradient.
Moving the aerofoil lower to be in-plane with the roof panel has again altered the trajectory of the Golfs wake to a steeper downward direction for both cases tested. Leading edge stall is exhibited within both case and thus accounts for the loss in downforce generated by the wing. And finally, lowering the wing to below the roof plane made the wake trajectory steeper still, whilst still stalling the aerofoils at their leading edges.


Image
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Flanker27
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Joined: Fri Jan 28, 2011 10:29 am

Re: Aero question

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Can you explain in simple words which one is te best configuration in your image and why?


p.s. i found and bought the spoiler "type 1" , it is original nissan and in the same colour of the car :D