[KVRC ~ish] CCE LMP01

[machin]

Interesting...

Looking at your diffuser I'm wondering whether the outward flare should start early and have a larger radius... So the outward turning of the air is less extreme as the air exits the diffuser .. Look at the transverse direction of the flow at the back of the diffuser! This might help with the flow above the rear deck as well... Also I wouldn't follow the line of the wheel fairing exactly with the strake.. I'd have it somewhere between straight and slightly curved... and/or maybe cut it short as per Wesley's idea?

Personally I'd also be inclined to move the outer-most strake in a bit so the gap between the wheel fairing and it is bigger: to see if that captures more of the rear tyre contact patch wake...




....But no doubt you have other things you want to look at...

[RicME85]

Wasnt sure where to start with the strakes so started the shape of the fairing moved inboard by 100mm.
No other plans at the moment so can do your proposal next

[machin]

I think what you did was as good a place as any to start... Essentially;

• Try something
• Look at the CFD results
• see if you can improve it
• Look at the CFD results
• etc...

I guess the more people play the better they get at getting the first "Try Something" right... But I think no one gets to the state where the first attempt works 100%.

[hollus]

By the way, this is a very interesting and rather educational thread. Thanks Machin for starting it and RicME85 for flooding it with CFD.

[RicME85]

New strakes have improved the downforce of the car.
Will post the numbers now and the CFD images later as busy atm.

[machin]

By the way, this is a very interesting and rather educational thread. Thanks Machin for starting it and RicME85 for flooding it with CFD.

Thanks Hollus... I think it is quite unique to see the design from clean sheet of paper right through design and development with all of the CFD in between... Very good of RicME85 to divulge all this data whilst competing in the KVRC, and for the input from the other KVRC competitors... I guess everyone wants to see nice tight competition....

New strakes have improved the downforce of the car.
Will post the numbers now and the CFD images later as busy atm.

About 4% increase in DF with very little change in drag or COP... Not bad.... But I still feel there's another "step change" hidden somewhere in that diffuser if you can find it!

[RicME85]

There is still some usable volume in the regulation box, just need to decide at which point to increase the diffuser volume ie the first half or the second half.

[RicME85]

[machin]

I'm still wondering if the lateral expansion is too much... The flow looks much better, but still not ideal...

...If you look at the shape of the wheel fairing behind the wheel, it looks like the original shape of the front suspension fairing (in a horizontal plane, rather than vertical plane, of course), where the flow from one side meets the flow front the other at about 90degrees, as opposed to a much more acute angle (10 or 20 degrees maybe?)...

The other downside of the lateral expansion is that the forces that are generated as a result of the change of direction (in accordance with Newton) aren't directed in a "useful" direction... They're horizontal towards the centre of the car (and rear wards), whereas a vertical expansion would direct the forces down (and still rear wards of course!)....

As an example: JJR's car has no (or very little) lateral expansion:-



I also see JJR has a much wider diffuser throat area... Looks quite extreme, but seems to work OK...

What were you thinking you'd try next...?

[RicME85]

I tried the 'square' diffuser exit on the last car submitted iirc. Can give that a go next then after that can look at changing the the underside of the wheel pod in front of the RWCL to gain a few mm to get a similar effect to JJR

[machin]

I tried the 'square' diffuser exit on the last car submitted iirc.

Half way between the two might be a better bet then...? But I would definitely taper the outer face of the wheel fairing if you do reduce the amount of flare on the inside face... To try and keep the rear face of the wheel fairing as small as possible and not end up with a big blunt face...

Will we get any other input before you go ahead with the next change (or are people not so keen now your car is creeping up near the middle of the grid)???!

[RicME85]

Yeah seems to of gone quiet since we have improved the numbers a fair bit!

What I might do is produce a few variations and post them here before running a simulation now that it's more of a case of refining rather than wholesale changes.
Good news is the AWS bill for September was only £16!

[TalnoRacing]

This has been a very educational thread, thank you to those openly sharing information.

Can someone please advise which Paraview settings are used to generate the image below? I am using version 3.98.0 and I have not been able to generate this type of view.

http://i.imgur.com/93kHlea.png

[LVDH]

Will we get any other input before you go ahead with the next change (or are people not so keen now your car is creeping up near the middle of the grid)???!

Sorry a bit too busy lately. But I have performed a test with a lower and higher front wing position as discussed a few posts earlier. Was not able to post the numbers yet. But the lowest allowed position seems to be the sweet spot.
Also I am waiting for you to implement my sugestion infront of the wheels. Non of the top three cars has this front wheel diffuser.
But I think the next large part you should work on is your rear wing. The car has a bit too much drag and I would not be surprised if it is the wing which is generating this. If the others are OK with it I could provide you with one or two.

[RicME85]

This has been a very educational thread, thank you to those openly sharing information.

Can someone please advise which Paraview settings are used to generate the image below? I am using version 3.98.0 and I have not been able to generate this type of view.

http://i.imgur.com/93kHlea.png

-Make sure SurfaceLIC is loaded (only need to do this once): go to tools -> manage plugins and expand the "SurfaceLIC" entry. Tick the 'auto load' box. You may need to restart Paraview. If you open the plugin manager again you should now see "Loaded" next to "SurfaceLIC".

-Open the case in Paraview. In the properties panel, tick 'internalMesh' and nothing else in the top panel, and 'U' and 'P' in the bottom panel, then click apply. After it's loaded, you should see a box.

-In the top toolbar, click the 'slice' button and click apply. You can position it before clicking apply, or re-position it later. You should now see a plane, probably coloured by pressure depending on your defaults.

-In the top toolbar, there should be a dropdown displaying "Surface". Change this to "SurfaceLIC". You should hopefully see some streamlines, but they will probably be invalid, all flowing in one direction.

-In the properties panel, look for the "SurfaceLIC: Integrator" subsection. The first element there should be a dropdown called "Vectors". In this dropdown there should be two "U" options with different icons. One of them should show the valid streamlines (the one with the small circular icon).

-At this point you now hopefully have the streamlines. You can play around with the other options in the properties panel, such as "Colour Mode" and "Enhance Contrast" to make it a bit easier to see the colours. You can also re-position the plane (top of the properties panel) to inspect different areas of the car). You can change which scalar field the colours are showing with the other dropdown in the top toolbar - you will probably need to tweak the range by using the range controls in the top toolbar.