07 aerodynamics gfr fsg workshop beg abstatt 20111029
TRANSCRIPT
7/30/2019 07 Aerodynamics GFR FSG Workshop BEG Abstatt 20111029
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Aero Design Process
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Name: Michael Wax
Task: Technical Director
Major: 3rd year Mechanical Engineering Student
About me
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Agenda
1. Introduction
2. Approach
3. Aerodynamics design process
Lap time Simulation
CFD Simulation
Testing
4. Results
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Customer requirements
Modular Design
Low Mass
High Downforce
Low Drag
Balanced center of pressure
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Designprocess Aerodynamic
Laptime Simulation
CFD Simulation
Manufacturing
Physical Testing
29.10.2011Management 8
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Laptime Simulation
Definition of raw concept
Do we want an aerodynamic package ?
Evaluate the most sensitive parameters
Calculation of qualitative results
Performance improvement in percent
Analysis of best vehicle concept for FSAE competitions
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What is a lapsim
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• comprehensive computer simulation
• allows chassis designers and race engineers toinvestigate the effects of car, driver, tire and
environmental variables on performance on a
race course.
You basically add the times you need to pass a defined part of a racetrack in a certain race condition
(Engine RPM, downforce, tire coefficient…)
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Laptime simulation
= ∗a = ∗ − =²
= ∗
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Laptime Simulation
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The tire model
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The aerodynamic model
• Aerodynamics drag increases quadratically with speed
=
∗ ∗ ∗ ∗ ²
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Sensitivity results
Downforce is the most sensitive vehicle
parameter
Vehicle weight as second most sensitive factor is less
important by a factor of 5
Drag on an aero-car the 3rd most sensitive
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Performance factors
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Concept comparison 4 cylinder car
Most common
Powerful
Relatively simple
4 cylinder car with wings
Powerful
Outright fastest
Most complex
Poor fuel economy
Single cylinder car
Most simple
Most fuel efficient
Lacking in outright
speed
Single cylinder car with
wings
Mix of speed and simplicity
Untested and unique concept
More complex than singleconcept
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Benchmark
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CFD Simulation
Evaluation of fine concept
Calculation of drag / lift coefficient
Iterate for the center of pressure
Calculate a rough number for downforce and drag
Ensure sufficient cooling under bad airflow conditions
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CFD Simulation
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CFD Simulation
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CFD Simulations – Boundary Conditions
3-6 Mio. cells (symmetry-plane)
k- turbulence model
Reynolds Averaged Navier Stokes
Rolling road / rolling tires
CFD Parameter
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Fine concept
2 part front wing
Best downforce by feasible manufacturing complexity
Sufficient supply of radiators
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Fine concept
2 part front wing
Best downforce by feasible manufacturing complexity
Sufficient supply of radiators
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Fine concept
2 part rear wing
Simulation complexity feasible
Manufacturing still reasonable
Satisfying downforce results
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Underbody Diffuser
2 Venturi Tunnels
Side Gurney Flaps, Tunnel fences, Rear Gurney Flaps
Fine concept
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Rigid Mounting and solid structure
Easy and fast to replicate
High quality surface
Easy to be implemented to the car
Sustain high ability to maintain the car
Manufacturing Concept
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Manufacturing
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Testing
Yarn Tuft testing to visualize stalling
Coast Down Tests:
Car will be slowed down from 100km/h only be essential resistance
forces (rolling resistance and drag)
Drag and downforce can be measured in pull and pushrods
Back to back Tests:
Standardized test track for laptime comparison
Evaluation of load distribution, package refinement…
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Coast down testing data
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CFD vs. Testing results
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Conclusion - Outlook
Improvement on performance could be clearly seen in the dynamicevents
A ~ 15% higher fuel consumption didn‘t hurt us in fuel efficiency.
Further development is focused on validation and weigt
decreasement
eCar with an aero package would not cause a decrease in
acceleration performance by a limited power output
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Thank you for your attention
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Laptime Simulation
Corner speeds are converged
Acceleration and Braking are transisioning
Both longitudinal accelerations are added
29.10.2011Management 36
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