(KVRC) TeamFuria TF14T

[AratzH]

Hi!

I am entering the 2014 KVRC and this is the car for the firts race.

















Lots of things to optimize, but looking pretty good compared to last year.

Any comments

[CAEdevice]

Very very good shape and color! Hope it will be as fast as it looks nice to see.

Are you working with SolidWorks and Flow Works? I would have many things to talk about : )
I used SpaceClaim for the first race, but I'm planning to switch to SolidWorks.

[AratzH]

Hi CAEdevice!
Indeed I am using Solidworks and Flow Simulation, which I believe is the complete version of flow works.
Anything you want to comment please feel free. I think we can both learn a lot.

[CAEdevice]

Hi, I'm not a CFD analyst so I have so many doubts about my CFD model.
I'd like to use SXW + FlowSim because it would be usefull to modify the geomtry using parameters and test it in the CFD environement, but first of all I should calibrate my "virtual" wind tunnel. At the moment ?ve found these difficulties:

- FlowSim doesn't inlcude the same turbulence model of OpenFoam-Khamsin (only k-eps, not omega-eps)
- The convergence of the COP value is quite difficult (I think it's the same for the official solver)
- Really have no idea of the right dimnesions fo the wind tunnel (I'm using a 30x10x10 box)
- When I run a steady state solution I obtain very low downforce (500N 100mph ...), only with a transient solution I receive reasonable results

About your car: I think that your front wing is simple but at the same time efficient, a similar concept of mine solution, but more evoluted

[el-Magico]

Left and right are not the same.. central air-intake as well as the mirrors?

[AratzH]

Good point el-Mágico. They are two different spec cars left and right. The one on the right didn't meet the kvrc rules so I had to modify it. Unfortunately with no time to test it right.

[AratzH]

Well, first results are out and I made it to the 5th position. Not bad, but my predictions where quite different haha.

Anyhow I discovered some flaws in my CFD simulations that made a 80% difference in the downforce and drag values compared to the official ones.

Now answering the questions from CAEdevice:

- FlowSim doesn't inlcude the same turbulence model of OpenFoam-Khamsin (only k-eps, not omega-eps)

- It is true that the turbulence model is different, and k-epsilon has some difficulties to solve things omega-epsilon does not. But bear in mind that the model used in FlowSim is a variation of the standar k-epsilon model and has many tweaks to deal with recirculations, adverse pressure gradients, etc. I wouldn't worrie to much about it. You should be able to get close enough results if you check other parameters.

- The convergence of the COP value is quite difficult (I think it's the same for the official solver)

- FlowSim also has problems with that, but, at least in my case, I needed almost half the iterations to make it converge. My tip would be that you put the COP as a Goal in FlowSim. It won't make it converge, but you will be more confident that it has.

- Really have no idea of the right dimnesions fo the wind tunnel (I'm using a 30x10x10 box)

-There is no consense in this either. Usually 7-10 times the characteristic lenght is used in the flow direction. In our case it would make it practically impossible to get results in a reasonable time. In my case I use 15m long, 4m wide and 4m tall. I only simulate half car and apply a simmetry boundary condition in the middle. This reduces the cell count and makes the calculation faster.

- When I run a steady state solution I obtain very low downforce (500N 100mph ...), only with a transient solution I receive reasonable results

-This deppends a lot in your set up, specially mesh size. Do you simulate tires? Do they rotate? What mesh size do you use?
Also in the case of wings it is of major importance that you have at least 3 mesh cells in the gap between elements. If you don't the wing will be treated as a single solid. Also I would recommend you to use the Advanced Narrow Channel Refinement and Optimize Thin Walls Resolution. These things will make a really big difference.

After analyzing the results given by KVRC I have been able to tune up my simulations and now I get a 2% difference in results. If you want I can check you simulation project and see if it can be improved. Anyhow if you follow my tips you should be close enough.

Regards!

[CAEdevice]

Hi AratzH, in the meanwhile I solved some problems (I confirm your solutions):

- K-epsilon model: I noticed that a bad mash (too big cells) influences the result more than the turbulence model (asked a colleague to test my geoemtry with a different solutor), expecially in the lower areas (the floor)

- Convergence: now I'm ok with DF and Drag, not yet wuth the COP (mine is 2.4m, the computed one by OpenFoam for the race was aout 2.0m). I defined as "goals" DF, Drag, Wings Drag, Wheels DF & Drag, and COP (torque/DF) as well.

I'm using both Narrow Channel Refinement and Opt Wall Thin Res.

Did you get 2% difference also with COP?

Yes. I think that to make a comparision with our virtual wind tunnel (with a moke-up car inside) could help.

PS: I think that your car will be faster than mine in more ordinary track like Magny Cours (look at your general efficency... it seems to be better): Monaco just requires lots of DF.

[CAEdevice]

I forgot the point about turbulence parameters: I'm using 0.1% for "turbulence intensity" and "0.0035" for "turbulence length". What do you think about?

[astracrazy]

are you able to do a few renders such as above but with the logos in the picture and your team name and number for the KVRC website and send them too me?

Thanks

[AratzH]

Not a problem!

[AratzH]

CAEdevice, 0.035 seems a little low, but depneds on the size of your smallest element. For Mónaco I used 0.1.

Now, some updates for the Magny Cours race. My car did great in drag, but had to low downforce. Also the CoP was pretty good, and I think it should stay in the same place. Updates are:

-Front Wing: New endplate, triple plane with different airfoils. Small winglets added.
-Rear Wing: New endplate, new airfoils, louvres added.
-Floor: Different expansion ratio, gurney aded, new leading edge, different distribution of strakes.
-Body: Optimized cooling intake dimensions (I was 10000mm^2 over the minimum!), optimized shape to avoid adverse pressure gradients, turning vanes added.
-Added a monkey seat to balance CoP.

And now the pictures:









And some comparisons between Monaco and Magny Cours:





As allways all coments are welcome!

[CAEdevice]

How many improvements! It will be difficult to keep my fourth place

[AratzH]

So, this is the package for Monza. Again lots of changes. Floor, body, front wing, bargeboards...
The following pictures show the new spec and the relative pressure contours. Nothing hidden this time









As usually all comments are welcome!

[Powershift]

i dont understand why the roll hoop air inlet is feeding air to the rear of the transaxle.