Quote:
Originally Posted by Nine8Six
E.g. in another coupled-CFD-vs-structural analisys that I've carried, i.e. by exporting node-to-node pressure/force from one mesh to another, I was able to carry a static (down)force analisys using the nastran SOL101 solver for each independent wheels (using a pressure plate/sensor under each wheel). This is how I've noticed that my rear-end was in-fact lifting at speed greater than 80km. Ran this at different velocity increments to then acknowledge that 120km/h is pretty much the 'safety limit' for my current set-up. Go Go eBay.com!!!
Additionally, and to make my simulation even more complex (bringing it to its knees) I've ran the same CFD but using shifting winds by offsetting the car in an angular X/Y position (15degree) to get a whole new set of data fields. Once ran transient I've noticed force/damping waves in the plots. The bounce was quite pronounced in the X plane (left/right dancing) but nearly invisible in the Z (up/down). Can't imagine what it would feel like cornering my car at 160km/h at my International circuit here (some fast corners on our SIC). Hope the software engineeres of the package I'm using got it all wrong LOL
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Sounds like you have some amazing tools at your disposal! Not that I can follow every detail of course, and I’m particularly puzzled about one thing.
I understand you are doing virtual aero modeling/testing using computational fluid dynamics. But you also mentioned putting a pressure plate/sensor under each wheel. You also have access to a windtunnel? Or … ?
Also, the 15 degree test at 160kmph you mentioned sounds like driving 160 with a 40+ kmph sidewind. That’s rather quick, so no wonder you got a left/right bounce! But I wouldn’t worry about experiencing anything like that when cornering at 160, as what is happening in the air should be quite differernt, no? For instance, suppose that on a 160 kmph corner you cross a line on the track perpendicular to your direction of travel. If your car is cornering neutrally, then the air that passes exactly over the center of your car when the front wheels cross the line will also pass exactly over the center of your car when the rear wheels cross it (Well, ignoring how the air might get pushed to the side or forwards by the car). That’s quite different from a side wind. (And also rather different from going straight. As the front and rear of the car pass the same line, they will be further to the outside. And as the middle passes it, it will be further to the inside.)
Also, even if what happens in the air were the same as with a side wind, 15 degrees is quite a lot. Suppose it was exactly like a side wind (with I can only imagine happening if you have four wheel steering such that the car stays pointing in the same direction, but it moves 15 degrees to the right or left). The wheels would have to be turned at least 15 degrees for that to happen, so your steering wheel would have to be turned, I don’t know, 240+ degrees? I would definitely worry about that at 160!