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 02-26-2012, 02:27 PM #269 (permalink) ERTW EcoModding Apprentice     Join Date: Jan 2012 Location: Toronto Posts: 120 Bu - '08 Chevrolet Malibu LS 90 day: 32.29 mpg (US) Thanks: 51 Thanked 65 Times in 31 Posts I'm already ahead of you drmiller...the solver finished this morning after 12 hrs and 373 iterations! I learned a huge lesson this morning. The goal plot was pretty flat at 100 iterations. Even at 200...and then around 220 it became a step function It was flat out until 350 iterations - and I was ready to stop the solver there...and then another step. wtf! It goes to show that what I assumed was "substantially" accurate may not be. I'll just let the solver finish from now on! A moving floor becomes useful below 5" of ground clearance. At 13", it's more free air, than ground proximity. If the under body is rough, then it may be of benefit to drop the car, and force more air over the body. If the under body is smooth, it's more beneficial to have higher ground clearance. It's a trade off that's best explored in a wind tunnel. I have the tail at 15°, and it still appears to detach somewhat. I hypothesise that ~12.5° is max. I believe the largest loss is the vortices. I think we could stop streamlines from migrating from the bottom, around the sides by widening the tail...more like a duck tail than a point. rho = 1.205 kg/m³ @ 273.15 K v = 30 m/s (108 kph) A = 2.138 m² (23.0 ft²) Fx = 108.68 N Cd = 0.094 Drag index = 0.20 m² (2.156 ft²) did I do good papa? Attached Thumbnails           Last edited by ERTW; 02-26-2012 at 02:46 PM..
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