No worries mate, glad I could be of help.
Mayyyyyyyyyyy need just a quick sanity check from you if that's alright mate...?
Sorry for the late reply, I was on holidayVyssion wrote: ↑Mon Apr 08, 2019 6:35 pmMayyyyyyyyyyy need just a quick sanity check from you if that's alright mate...?
So, following on from the "success" of the empty domain which has a curved velocity field now, I went home at set up my F1 car model with it:
Set it all up to go and executed it etc, and was greeted by this:
Which looks somewhat sensible... however, the Coefficients of [Total] Pressure's etc, were completely off the charts... For example, there seems to be a somewhat "higher" pressure throughout the domain which I cant work out is the dynamic pressure of the rotating reference frame being interpreted as just an arbitrary static pressure increase by the stationary frame, or whether there's some sort of mistake in the definitions of my equations... So I did some research on Keogh's paper and found these two little gems:
Now, I took these, and basically reassured myself that the "setup" was correct (I double and triple checked it), and so I'm sort of left wondering how to interpret the field data when it comes to defining my own custom variable equations... For example, CFX doesn't calculate Pressure Coefficient by default - you have to create an expression, convert to a variable, then plot it. Here are my current equations as ANSYS requires you to define them just for completeness:
It was interesting to define the velocity field algebraically via the "omega * r" definition he has, then to define the Pressure Coefficient based on this new "Curved Velocity" as I called it arbitrarily. However, when I created this new CP variable and plotted it, I thought I might just swap out the Pressure field for Total Pressure field... There is a "Total Pressure in Stationary Frame" which exists as well that kind of "removes" the radial component of the rotating reference frame from the Total Pressure, but I just left it as this for now. And what I got out of it, did look remarkably similar to what I was getting before the curved flow adaption was made:
However... the upper and lower bounds extend from like -0.0005 to +0.00009 or something insane... and then I look at the units of degrees^2..................... Which makes me wonder if it is somehow generating a dimensionless parameter in terms of area on a sphere...??? (i.e. in terms of "steradians" of a full sphere -- equal to 41,253 degrees^2)...
I feel like this is soooooo close to being correct etc, but I am missing something in terms of units or variable etc... Any thoughts on it??
How about doing what you have done here but with a 2007 spec front wing? See how they wings helped or hindered the airflow.Vyssion wrote: ↑Mon Mar 04, 2019 10:44 pmAlright...
So, over the past week or so, jjn and I have been CADing up some 2019 spec wings for the PERRINN model in the future. jjn has created a "somewhat parametric" aerofoil profile distribution which allows us some control over the geometry, and hopefully we can take these models, and after I prepare them for meshing, get some of our own "design attempts" out there too (or rather, more likely, we will CAD up something similar to existing teams wings and see if we can make any assumptions on performance... but shh!!)
For now though, we have somewhat "modified" the 2018 wings of the Perrinn to fit the 2019 spec and CFD'd them for you. I will say that I wanted this to be the start of what will eventually become a "replacement" of all components of the Perrinn F1 model. The export of the baseline Perrinn CAD to .step was "dubious" and has taken me around about 20+ hours total of surface repairing and preparation for meshing, to the point now where part of the issues I am having with the meshing is that generating a patch conforming tetrahedral mesh is doable... just!! The inner "perfectionist" in how I prepare my own CAD for CFD is getting more and more frustrated with the lack of attention to creating good quality surfaces, most likely because the people running simulations just stick a mesh wrap over it and accept whatever it spits out. Not me...
Anyways, so... This time, I have prepared the CAD to a much higher standard (FW and RW only of course) and have replaced the originals. The result is a much higher quality mesh for the FW and RW, as well as, with many... MANY... meshing attempts... a slightly better overall quality mesh. I have now put our new geometry through a 4° Yaw case (similar to before) and finished post-processing as well.
The results are now in, and both jjn and I are studying the images and forces/torques outputs etc and will be back sometime soon with another update etc, but for now, here are some images of the new wings.
Hmm... That's kinda a bit tricky to do I think for not that much reward...
Awesome, thanks for the reply I will check it out and start playing around with the model.jjn9128 wrote: ↑Tue Feb 19, 2019 12:29 amThe Perrin model is an opensource project available from onshape, which is an online CAD program. The car can be found here. Not sure if it will force you to create a profile to view it or not. Onshape is made by some guys who left solidworks, if you've used that it'll be familiar but I think it's not quite as good, e.g. I wouldn't even bother trying surfacing.boerface16 wrote: ↑Mon Feb 18, 2019 11:13 pmVery cool topic, thanks for sharing! I am interested to see what you guys will do in the future. I would love to know how you got the model? I am interested in playing around with this
Personal question that you don't have to answer, whats your background?
Thanks mate. Unfortunately, I don't think I'm gonna have time to devote to this for a little while yet, but I do miss it; and I also really want to hurry up and get my new computer so I can run these much smoother given I wont be maxing out my current machine.boerface16 wrote: ↑Thu Jun 06, 2019 9:01 pmAwesome, thanks for the reply I will check it out and start playing around with the model.
Also, I just took a look at the rest of the thread... great work guys! Very insightful, interested to see what else you guys come up with in the future.
I am having a think about the curved domain Cp0 problem, the degrees^-2 is really tripping me up... there has to be an error in units of something right? Did you double check to see that everything else gave you the units you were expecting? You probably have but just in case...
Vyssion wrote: ↑Thu Mar 14, 2019 12:04 pmHi all,
As mentioned earlier, here is our new article going through some of the findings that jjn and I have seen with the 2018 vs. our 2018-modification to 2019 spec wings on the Perrinn baseline model.
Please give it a read, and let us know what you think!!
(p.s. 2019 Vyssion-jjn wings have been CFD'd at 0° gust; just waiting on 4° gust now before we release those pictures and gifs to you all ... stay tuned!!)
https://f1tcdn.net/images/features/2019 ... 19-big.png
I don't really know of a "one size fits all" guide to be honest, as there is quite a lot of, kinda, "expert guesswork" in just knowing how the mesher and solver are likely to deal with the flow or mesh as you create it... Some of my advice would be to:peaty wrote: ↑Sun Jul 14, 2019 12:18 amI just found your work and it's amazing!! are you working with Fluent or CFX!? I would love to learn to run simulations. Could you please recommend me a good tutorial that covers the entire process -from surface preparations to post-processing-!? I've been trying to find a good one without luck so far!
You can find the Perrinn car via the usual channels (https://www.onshape.com/cad-blog/this-2 ... ublic-plan). Anything we added for the purpose of this thread and our front page articles is ours. Sorry.Jonas wrote: ↑Wed Nov 06, 2019 7:59 amHey,
can you please send me the CAD Files of the PERRINN F1 Car, so i could do some simulations with about 80 mio to 120 mio cells and a Y+ lower 5 in star-ccm+. Tires will be modeled with MRF and if you want, i can also do cornering simulations in a MRF region.
I can use free licenses and a high performance Cluster with more than 17k processors
Feel free to contact my by private message...
Best regards and really looking forward to simulate the car,