I don't think it makes sense for vibranium to be immune to aerodynamic forces, because those forces are what let it function like a Frisbee when thrown. The same physics that create drag also create lift, so you can't take advantage of one without being subject to the other. Vibranium isn't super-heavy. Wikipedia says it's got 1/3 the specific gravity of steel, making it a bit lighter than aluminum. After all, Steve isn't superstrong in the comics, just peak-human strength. The shield isn't Mjolnir.