41 replies to this topic

[Ethel]

Eulerian solvers, weren't they in an episode of Dr Who? 

 

It's a bit unfair comparing Minis to bigger cars. There's still room for 4 adults in there, so the CD is bound to suffer for something that so closely wraps that passenger cell, even without the exterior seams. CD multiplied by frontal area is the minimum for performance comparisons & you ought to work length, interior space & weight into your formula to compare one design against another. Comparing required BHP for speed and/or acceleration plots would be simpler.

 

It would be interesting to see what you could do with the seams, short of removing them altogether.

[Cooperman]

Indeed. Over the years it has been the 'add ons' which have so increased the drag over what it had originally.

The wheel arch extensions, those huge wide mirrors on both sides and, in the later cars the ultra-wide wheels have all contributed to a drop-off in overall performance, including fuel consumption, for no actual gain anywhere. In fact the Minis which handle best are those on 145 width tyres and arch extensions are not needed to run those.

[Alex_B]

 

I don't have access to on unfortunately so I will be doing it the old fashioned way on solidworks

 

Just googled "classic mini cad model" and found this:

 

http://www.3dcadbrow...px?3dmodel=5510

 

Dunno if you can use it. Plus don't really trust the solidworks solvers. Surely it would be better to mesh the car in an actually FEM/CFD package and solve using that programs built in eulerian solvers.

 

I have a copy of that model I think (one similar) and its not accurate enough to aerodynamically test, plus its one huge assembly opposed to a single part and thus a nightmare to get through aerodynamic tests without errors. Still don't know if I have the time to do this but if I did I would be building the model on solidworks then creating the mesh and what not in ANSYS, then running it through, so that gets rid of the issues with solidworks mostly :) (Incidentally this would have to be done at my University, I don't have the money for the licences of the above software! ) 

[rally515]

Juat an idea with regards to the seams on the Exterior here....

 

Wouldn't a simple GRP seam strip, much like the standard metal seam strips be more drag efficient if they were angled out on either side ?

 

Might look abit odd but principle over form!

[Vinay-RS]

 

 

I don't have access to on unfortunately so I will be doing it the old fashioned way on solidworks

 

Just googled "classic mini cad model" and found this:

 

http://www.3dcadbrow...px?3dmodel=5510

 

Dunno if you can use it. Plus don't really trust the solidworks solvers. Surely it would be better to mesh the car in an actually FEM/CFD package and solve using that programs built in eulerian solvers.

 

I have a copy of that model I think (one similar) and its not accurate enough to aerodynamically test, plus its one huge assembly opposed to a single part and thus a nightmare to get through aerodynamic tests without errors. Still don't know if I have the time to do this but if I did I would be building the model on solidworks then creating the mesh and what not in ANSYS, then running it through, so that gets rid of the issues with solidworks mostly :) (Incidentally this would have to be done at my University, I don't have the money for the licences of the above software! ) 

 

 

Hmmm, Yeah you wouldn't particularly care about the car being an assembly. If you could convert it to a part (I think you can do this in solidworks (correct me if I am wrong)) then import it as a .step file into an FEM package like abaqus/autodyn and do the meshing and solving in that package.

 

Yeah and I know that research licences are a killer, so I mean provided you don't use the results for monetary gain, there shouldn't be a problem in using the university licence. I figure this is more out of interest sake, so that you (and others) can improve the fuel efficiency and performance of the mini.

[Vinay-RS]

Just a thought, based on what has been suggested here:

 

- Why not create a base model (regular wheels, no arches, no mirrors).

- Then run the simulation and obtain the Cd

- Then add these components, in different combinations and different specs,

- Calculate the Cd and then determine which combination has the greatest effect on the Cd.

[mab01uk]

Dave Vizards 'Mini Tech News' magazine March 1982 (available long before all the current Mini magazines appeared in 1990's)

(also note me listed as 'Roving Reporter' )

I have yet to find the more in-depth technical report on Mini aerodynamics that I have stored away somewhere in the loft.........

 

'Mini Aerodynamics' article and diagrams below by Peter Davney

 

 

 

 

 

Edited by mab01uk, 20 July 2014 - 10:52 AM.

[Gr4h4m]

flat bottom mini will help a lot with top speed. some boot floor mods to get the exhaust out of the way, and then some ally sheet. 

[JimF]

Love aerodynamics! Fascinating stuff!

[jakejakejake1]

There were a series of articles done in race car engineer a few years back regarding drag reductions and downforce increases with minis, i will try and find a link or something to them as they were quite interesting

 

Edit: Here is the overview by Carbon Weezel, the search is ongoing regarding the original articles which had more detail http://www.carbonwee...sting_mini.html

 

Edit 2: The search continues, but there is mention that Feb 2010 Mini World has the article on Aerodynamics, starting pg 60, but I have yet to confirm

Edited by jakejakejake1, 21 July 2014 - 07:25 PM.

[Cooperman]

flat bottom mini will help a lot with top speed. some boot floor mods to get the exhaust out of the way, and then some ally sheet. 

That is a good idea. My 'S' has a full length battery box shield down one side of the centre exit and a shield for the twin electric fuel pumps down the other side.

It helps keep the DGS from the inside of the subframe webs which reduces rusting as well, so it's 'win - win'.

[mab01uk]

Back in the 1970's many Free Formula Special Saloon Mini racers cut out the boot floor to save weight and then added an aluminium undertray under the rear subframe curved up to the rear panel. This also allowed a small petrol tank to be fitted low down within the rear subframe. The exhaust on our racer passed through the undertray while some were diverted out sideways just in front of the rear wheel.......

This was my brothers 850 Special Saloon Mini racer below with a sheet aluminium undertray back in 1973.

 

Edited by mab01uk, 21 July 2014 - 10:54 PM.