We are doing some CFD analysis of a MK1 over on the US MR2OC

[Bill Strong]

Can you guys come over and offer some of your expert opinions?

http://www.mr2oc.com/showthread.php?p=2630951#post2630951

I am not an engineer, but I do read a lot of engineering books and play with real life cars. So this stuff is of great interest to me. I know that you brits are also into the next level of design and not just into 200mph paint jobs. :)

[Barronmr]

That thread is a great read, unfortunately I've no idea about flow dynamics.

Anyone know if a mk1 could be made as aero dynamic as a mk2?

Co-drag eff for the mk2 I think is 0.29 (not 100% but thats what my memeory says)

[nik]

wow...v.interesting..wish this was pre-mr2only article on aero..!!
will come and join in after ive had some sleep..

[Paul Woods]

a great thread indeed! wish i could contribute but sadly my knowledge in this area is practically zero.... makes very interesting reading though!

[biteme]

That's one hell of a read. Waaaay over my head though. Sorry, Bill.

[Bill Strong]

Oh come on! Brits are more highly edumicated in this sort of thing :)
A-levels and all and on 4-channels of TV should make you much smarter! lol
My oldest (22 years) was educated by the English system! and she is really smart!

I am actually not wanting to make an aero MK2 copy. what I want to accomplish is to make a stable 200mph MK1. That and make my race car (4age powered) faster up the hills.

[Bill Strong]

http://www.mr2oc.com/showthread.php?t=250308&page=2&pp=30

hopefully this explains it a bit better... but remember... I am not a trained engineer, I am only book taught and am pretty much guessing at some of this.
So please do not take my posts as absolute fact. remember, I am a yank

[randomfactor]

Any chance of posting the article here. I don't have a username for that site, but two people I know have phD's in CFD if that's any use?

[Bill Strong]

just sign up, it is free. and I wont spam you or sell your info. I own the site

[Jim-SR]

ive been trying to lend my expertise on there for a while Bill. at the moment i have PM'd the guy who has the working Floworks model to see if i can get a copy of his (i had the same model originally from BenTheSwift but couldnt get the geometry to work out) to run some of my own testing in 2 CFD programs to corroborate his results and to push the development as far as we can. the more people working towards the same goal, the more data we should collect hopefully :)

there is certainly some interesting points being raised thus far though. all of the results have to be taken with caution i think though, as we are grossly simplifying the shape of the car, the effects of surfaces and external conditions, and as far as i can tell the model is being run at a fairly low resolution. however it does give a fantastic starting point for people to make changes to their cars aerodynamics, and then develop things further practically. its finding a starting point which is most important IMO

[Bill Strong]

the latest guy to come forward with the super awesome rendering is our best choice, If we can get him to do the engine, front and rear trunks like he did with the GT car we could move light years forward.

Yes I understand about the caution bit. I would really like to see a top view showing the flow around the mirrors to reinforce my DIY yarn tuffs test.

[Bill Strong]

I also think that the more people that we can get involved, while keeping some sort of control and organization, we could get some real good information from this

[Jim-SR]

the super rendered model might struggle big time to compute though. also its done in 3ds max, which is more of a design suite than an engineering suite. it doesnt have in-built CFD, and i have my doubts about its accuracy at exporting in any engineering format. the only way i personally could test it would be as a Parasolid, there are probably other softwares that will allow other formats. it looks superb, but as said, i have my doubts in terms of engineering accuracy

there is little point in pushing for a 100% accurate solid model when the CFD calculations themselves are only being run at low refinement levels. short of us acquiring the use of a supercomputer (something i am going to try and look into next week lol) it is hard to accurately compute in any real detail. these results dont need to be perfect, they just need to find a starting point for practical development IMO

[MartG]

Very interesting thread you've got there Bill - like you I'd love to see the effect of a Plumley spoiler and papal vent, as the trackday car I'm currently building has both those features :whistle:

The high pressure area ahead of the front skirt makes me hopeful the other aero mod I've got planned will be useful too - a horizontal plate splitter fitted to the underside of the nose, extending maybe 100-150mm forward of the front skirt and rearward to maybe 150mm behind the base of the radiator. Don't know if it'll unbalance the car at speed though, with the added front downforce ( or reduced lift anyway ) not being matched by a similar change at the rear, unless the Plumley is a lot more effective than the standard location. My Plumley has its leading edge about 20mm behind the edge of the bootlid ( pics here http://forums.twobrutal.com/showthread.php?t=7581&page=3 ) - if I do get an excess of front downforce I may try fitting a Gurney flap to the rear spoiler too.

It would also be interesting to see the effect of a rear diffuser - though as you've already pointed out the rear underbody on the model is far to low, and should really be curved to mimic the exhaust silencer.

Lots of food for thought though :thumbsup:

[Bill Strong]

I have also pointed Deno Plumley and Bruce Plumley to this thread. They have done a lot of work on the aero of both Deno's MK1.5 and his fathers SC. I know that Bruce could add to this. But he seems to spend a lot of time in the South of Spain! :) damn retirement!

[Paul Woods]

when all of the serious airflow work has been done can we model the effects of a dogs head sticking out of the passenger side window? :)

Being serious for a moment id like to see the effects on airflow with and without the cars undertrays.

[Jim-SR]

when all of the serious airflow work has been done can we model the effects of a dogs head sticking out of the passenger side window? :)

Being serious for a moment id like to see the effects on airflow with and without the cars undertrays.

just bolt flat ally sheet under the entire underside of the car and have a flat floor :D

[Paul Woods]

just interested to know if the stock undertrays actually do anything

[biteme]

Are thinking of a rear diffuser?

[Paul Woods]

indeed mate,just wondering if theres a good case for one.

[Bill Strong]

good point. This is a street car. All my aero books state that all those extra bits really only work well on purpose built cars. Now they may make just a bit of negative lift, but hardly any 'downforce'.

But having a rear tray that extends at least to the leading edge of the american bumper would be cool to see tested.

[biteme]

Agreed Bill, rear diffusers only work when the front airflow is sculptured to make the most of the rear diffuser.

[superchargedAW11]

the latest guy to come forward with the super awesome rendering is our best choice, If we can get him to do the engine, front and rear trunks like he did with the GT car we could move light years forward.

Yes I understand about the caution bit. I would really like to see a top view showing the flow around the mirrors to reinforce my DIY yarn tuffs test.

Thanks! :jump:
Backspace from mr2oc.com here. I modeled the MK1 with the fancy renders and the GT-ONE with full engine bay.

I'd love to help out Bill, I'm going to continue to model the underbody of the car as well as the radiator/engine bay sections.

Any blueprints, or sketches even- of a cutaway view of the front radiator area and engine bay area would help me out so I can get working on this.

I've got RealFlow which is a fluid dynamics simualtion program which i'm sure can be manipulated to simulate airflow. I'll be playing around with that after I get the model ready.

[Jim-SR]

can 3ds models be exported in parasolid format? and is there an option within 3ds to create an inverse model (e.g. the solid parts become hollows within a larger solid block)?

if so then i can run the model using Fluent Flowizard, as this is the format it accepts. it has to be inverted though so that the solid part is the air, and the hollow part is the model.

[superchargedAW11]

Nope, I don't see parasolid as file type as an export option in 3ds.

In 3ds there is a function that will let you subtract one object from another (to create an inverse model like you said) 75% of the time it doesn't work worth a damn on simple objects, so I doubt it would work well with anything complex

[adamh]

wow.. getting a bit zoom in here!, amicable idea bill. I briefly met someone a while back who built a minature wind tunnel to test scale models of car shells they making. .. was for a land speed record or something like that. I've no idea about air flow and stuff but it seemed like a novel solution to building a full sized one, just a passing ramble ! software is amazing these days that's for sure

[Jim-SR]

problem with scale wind tunnels is that in order to accurately model flow you need to run the air faster proportionately to the model size

e.g. a 1/8th scale tunnel requires air to flow at 800mph in order to accurately model real-world airflow over the full scale car at 100mph. the problem here being that you are now into supersonic air speeds which brings with it a completely different set of physical rules, so its not useable

1/5th is about the smallest you can get away with, and you still need air flowing at 500mph, which then requires a much larger motor unit, etc. 1/3rd-1/2 scale is where its at, but it requires a lot of space, and making models is then very expensive. CFD testing, whilst not entirely accurate, can give a fairly good idea without any of the expense, just the initial outlay on software and a fast computer :)

[Gary Symons]

From the Autodesk website:

Supported Scene Import Formats

3DS, AI, DDF, DEM, DWG, DXF™, HTR, IAM, IGES, IPT, LP, LS, MTL, OBJ, PRJ, SHP, STL, TRC, VW, WRL, WRZSupported Scene Export Formats

3DS, AI, ASE, ATR, BLK, DF, DWF, DWG, DXF, HTR, IGES, LAY, LP, M3G, MTL, OBJ, STL, VW, WRLI see that 3ds will export to IGES, this would get it into most cad systems. The main downside is that it will convert a solid to a series of faces so you would possibly need to rebuild the model in cad to create a proper solid model (i.e. parasolid)

[Gary Symons]

Just done a little test here at work and the cad system I use can recombine (sew) the faces of an imported iges file back into a solid.

I have no knowlede of using cfd software (yet) but is there any chance of an iges model of that fine looking virtual MK1 :pray:

BTW I use Unigraphics NX4.