[KVRC] Khamsin Virtual Racecar Challenge 2016

[CAEdevice]

I don't know if it will be enoguh to solve the problem (I have not done any simulation with a geometry similar to yours), but it could help:

[machin]

I can't see Matteo's image due to the company firewall so he may have already shown the same thing I am about to describe... But I suspect that the outlet on top of the "bonnet" probably isn't as good as a position directly at the back of the car; the air coming out of the duct has to displace the air travelling over the bonnet, which is another quantity of pressure that the cooling flow has to overcome. i.e. if you ran the simulation with the ducting closed off I suspect that the area where your ducts are located would be grey (ambient pressure), whereas you want to put them in a blue area, low pressure, like the back of the car.
I would be inclined to open up both the inlet and outlet: probably more than you think is necessary at first: you should then get full power but at the expense of additional drag, but at least then you can gradually close them up until you have enough flow with minimal drag. A side note: with a real radiator you would want to incline them forward at the top (rather than backwards as you have them) so that the flow is aligned better with the fins on the radiator, but I don't think this matters on our simplified radiator model.

[CAEdevice]

I think it quite matters, if you look at the detail of the surface LIC picture, you will see that the flow near the heat exchanger is perpendicular to its outlet surfaces.

I agree: a heat exchanger mounted in that place would be vertical or slightly inclined forward.

[etsmc]

I too would agree that the heat exchanger should lean foward but i couldn't get it to fit in the design.
The cooling outlet in the center of the car was a quick fix and has now been removed.
I will get an image of the outlets now they are larger for your opinion on the position. Interesting that Matteo has suggested the change to the lowerside of the front diffuser is this just to facilitate the cooling duct or to help with the diffuser flow.

[CAEdevice]

No, sorry I have not written it: the changes in the lower part of the diffuser is just a suggestion to improve the DF.

[LVDH]

I would not agree on changing that part to improve front down force. But the fun of CFD is trying it out and learning why one design is better than the other.
Around the large "X" Matteo drew seem to be two inlets. Could you please explain what they are?
Also showing static pressure or even better the pressure coefficient would help to understand the pressure distribution and situation around your cooling system. Also keep in mind that the Bernoulli law only holds true if no energy is dissipated along the path line.
My very first MantiumRacer had a similar cooling design like your car. The stagnation pressure of the cooling inlets was used on a splitter in front of them. It was very difficult it get it complaint with the old rules. With this year's rules it should be much easier. I was unable to get good front end down force (not to say that my very first entry did). I hope you are more successful.

[CAEdevice]

Also keep in mind that the Bernoulli law only holds true if no energy is dissipated along the path line.

True. In the example, I think that considering the energy dissipation would describe an even worse situation.

[Alonso Fan]

Have all the simulation results been sent out now? Still waiting for mine

[cdsavage]

Chris, is there any chance of having the intro bodywork changed slightly? I dont know about Richard, but I find the front wheel pods could do with being a bit shorter (start a bit further back). This would give us a bit more area to play with for creating front downforce. I found it difficult to add downforce at the front without affecting the cooling (which we obviously cannot move to counter issues faced).

I would probably prefer to leave it as-is, since it's meant to serve as a constant baseline. If everyone in the introductory class was happy to do so, we could switch the front wheel pod to an optional part, which can be resubmitted as-is, or modified/replaced with a custom part.

Did Will submit for Round 1?

No entry from Will this round. There were 3 entries in the intro subclass.

Have all the simulation results been sent out now? Still waiting for mine

There were some problems with the simulations for sjns-Racing and SHM Racing - I think Julien is re-running these. I suspect there were also some issues with some of the other simulations - we need to look into this before releasing the results.

Images for the round 1 entries have been posted here: http://www.khamsinvirtualracecarchallen ... -1/round-1

[sjns]

There were some problems with the simulations for sjns-Racing and SHM Racing - I think Julien is re-running these. I suspect there were also some issues with some of the other simulations - we need to look into this before releasing the results.

Not again! I was so confident I solved the issue on the outlets. I did several runs that worked perfectly. So dissapointing to hear that something is wrong again. Im sorry for the delay. If there is anything i can do let me know.

[etsmc]

Well, I have tried to open up the cooling intake, exhaust and duct now my only issue is Chris with his compliance check as to whether the bodywork is thick enough in this area.
in the image, you can see I have tried to help the flow out of the heat exchanger but I think that half way down the duct may be a choke point... the other issue I have to contend with in this area is the foot box template.

I may go with Matteo's suggestion and reduce the severity of the diffuser to allow for a larger duct and change the leading edge of the floor


will have to see if I can get OCCFD to work with the post processing to see if it helps

[CAEdevice]

You should try to incline the heat exchanger forward.

The front double diffuser is (could be) a feature that increases df, but your priority now is to use 100% of the available power.

[etsmc]

so more of this sort of arrangement.


i still have the issue of the footbox

[RicME85]

Would it not be better to do this:


As it stands you are asking the air to change direction and giving it a place to recirculate. Although what I have proposed is tight and not ideal near the heat exchanger, it isnt asking the air to do as much.

[wesley123]

I'm not informed about the regulations regarding cooling, but changing to a more group C-like solution might be beneficial.


It could help retain your diffuser profile and, afaik if done properly, it can reduce drag as well.