Wind Tunnel DebriefTitanX Presentation

Dylan Bruce

9/5/14

• Verify aerodynamic forces from CFD

– Drag, Downforce, L/D, Distribution

• Assess CFD and new turbulence model for accuracy

Goals

• No rolling road, eliminate as many variables as possible

Geometry

Yarn!

• Wind Tunnel Test plan created to isolate variables

Analysis

Qualitative• Boundary Layer on table• Under/Over FW,RW (each element)• Vortices around endplates• Flow Between Front endplates and Nose • Midplate/DRS gap• Rollhoop• Headrest Shroud/RW interaction• Flow over/around Driver• Radiator• Cooling Duct• Intercooler• Flow over chassis/interaction with aero• Tires• A-Arms• Supports/Mounting• Under car• Out of Diffuser• Shocks interference with underside flows • Any interference from straps or other equipment• Windshield/dash• Side gurney flaps • Turbo Scoop

Quantitative• Straight• 5, 10, 15, 20 degrees Yaw• Accel Setup (All secondary and tertiary elements at

“max up” position)• RW

• Tertiary 30, 40, 50 degrees• Secondary 7, 16 • Secondary 16, Tertiary 50• Secondary 16, Tertiary 40• Secondary 16, Tertiary 30• Secondary 7, Tertiary 50• Secondary 7, Tertiary 40• Secondary 7, Tertiary 30

• FW• Tertiary 22, 32, 42

Car set up on elevated test platform– Eliminates inconsistencies due to boundary layer

– Car scales inset in platform to measure downforce

– Load cell fastened to nose with different yaw settings

Tunnel Testing

Flow separation on tertiary element consistent with simulation

Vortices off endplates and front wing are easy to visualize in the

tunnel

Flow separation and visualization

• Standard CFD set up for all but yaw simulations

– Slip symmetry on top, bottom, left, and right

– 0 Pressure on rear

– Relative velocity on front

• Yaw at 5 degrees run CFD only

– Slip symmetry on top and right side

– Component breakdown applied on bottom

– Relative x velocity applied to front, relative y velocity applied to left side

CFD Set Up

Straight Set Up Results

CFD Tunnel Percent Difference Percent Difference

Set UpSpeed (mph)

Drag (lbs) DF (lbs) L/D

Speed (mph)

Drag (lbs) DF (lbs) L/D

Drag (lbs) DF (lbs) L/D Drag (lbs) DF (lbs) L/D

Straight 15 8.600 15.300 1.779 15 15.483 24.600 1.589 44.455 37.805 -11.973 Average 9.538 -14.360 -26.043

Straight 20 15.500 27.900 1.800 20 19.174 25.900 1.351 19.159 -7.722 -33.252 Variance 245.315 440.301 51.077

Straight 25 24.600 43.100 1.752 25 29.508 38.200 1.295 16.633 -12.827 -35.338 Standard Deviation 15.663 20.983 7.147

Straight 30 40.400 70.000 1.733 30 41.072 57.100 1.390 1.636 -22.592 -24.631 Average Error 5.221 6.994 2.382

Straight 35 55.930 93.800 1.677 35 54.851 72.400 1.320 -1.967 -29.558 -27.059

Straight 40 71.100 120.200 1.691 40 74.289 95.800 1.290 4.293 -25.470 -31.097 ρair (kg/m3) mph to m/s lb to newton

Straight 45 91.700 154.000 1.679 45 90.529 121.100 1.338 -1.294 -27.168 -25.543 1.1789248 0.447 4.44822

Straight 50 113.300 191.400 1.689 50 106.276 150.300 1.414 -6.610 -27.345 -19.450

Acceleration Set Up Results

CFD Tunnel Percent Difference Percent Difference

Set UpSpeed (mph)

Drag (lbs) DF (lbs) L/D

Speed (mph)

Drag (lbs) DF (lbs) L/D

Drag (lbs) DF (lbs) L/D Drag (lbs) DF (lbs) L/D

Accel 15 4.100 4.700 1.146 15 12.039 2.700 0.224 65.943 -74.074 -411.120 Average 1.234 -38.866 -79.388

Accel 20 7.300 11.100 1.521 20 12.039 5.600 0.465 39.361 -98.214 -226.877 Variance 847.392 728.779 18356.3

Accel 25 11.600 14.400 1.241 25 12.285 12.100 0.985 5.572 -19.008 -26.031 Standard Deviation 29.110 26.996 135.486

Accel 30 18.000 22.400 1.244 30 15.483 16.500 1.066 -16.257 -35.758 -16.774 Average Error 9.703 8.999 45.162

Accel 35 24.000 30.700 1.279 35 20.896 27.600 1.321 -14.855 -11.232 3.154

Accel 40 31.300 39.200 1.252 40 27.786 29.800 1.072 -12.647 -31.544 -16.775

Accel 45 39.800 49.700 1.249 45 34.429 42.300 1.229 -15.600 -17.494 -1.638

Accel 50 49.200 60.900 1.238 50 41.565 46.000 1.107 -18.370 -32.391 -11.845

Accel 53 54.600 67.900 1.244 53 44.740 52.200 1.167 -22.040 -30.077 -6.585

• In the simplest form, CFD is proving to be a reliable platform to base other aspects of the car off of

• It is hard to get specific data for cooling scoops and shrouds; however, we are seeing magnitudes consistent with simulation in the general area

What We Learned?

Without the time and space you donate, collecting data like this would be much more involved and less reliable.

We now have great data to discuss with judges at competition and numbers to crunch as a team. We look

forward to working with you in the future!

Thank You TitanX!