Questions
Pts Prob MSTE 482 Motorsports Aerodynamics : Assignment #3
30 # Fall 2021 Name:
An assignment relating to understanding of lift vs drag trade-offs
Show all work in the space provided. If you want partial credit for a wrong answer, you will make the work neat and legible.
Place final answers in the pale yellow space provided.
Turn in printed paper copy in portrait format: on 8 1/2 x 11 std American size pape
For graph/table problems, print new data table and graph and your answers only.
Estimate 5-7 sheets total printed and stapled with names on all sheets.
Also turn in electronic files for validation if you have done any work in Excel.
Some conversions and constants:
1 bar = 14.5 psi = 29.92 in.Hg
Rho at Sea level is XXXXXXXXXXlbsec2/ft4
1 mph = 1.61 kph
1 Mpa = 145 psi
g in US units = 32.2 ft/sec2
STP: 59 deg F and sea level STP: Density XXXXXXXXXXkg/m3 or XXXXXXXXXXlb sec2/ft4
Dynamic Viscosity XXXXXXXXXXx 10-5 Ns/m2 or 3.805x10-7 slug/(ftsec)
Kinematic Viscosity XXXXXXXXXXx 10-5 m2/s or XXXXXXXXXXft2/s
1 hp = 550 ft-l
sec
Indycar in roadcourse configuration:
Frontal A: 14.0 sq ft.
Power 750 hp at rear wheels at STP.
Wt 1950 lb with driver and full fuel
Car makes 5010 lbs Df @ WT conditions
Cx nominal = 1.000
5 1 Write out the full balance equation for calcuating top speed in terms of driving force equals resistive force.
Do not move the V for the driving force term to the other side.
Use Excel to generate graphs and polynomials (1st or 2nd order) for 'everything' that is velocity dependent. (Driving force, rolling resistance coeff, aero drag, Df, etc)
Graph forces vs speed and coefficients vs speed
We are going to assume the engineer has selected the co
ect gear to achieve peak power at Vmax
Rolling Resistance friction Coeff Indycar's Speed effect from aeroelasticity and compressibility :
Speed mph fR Speed Cz Cd
0.0 0.010 205 3.500 1.000
88.0 0.015 235 3.400 0.980
124.7 0.018 265 3.300 0.960
161.3 0.022 295 3.200 0.940
205.3 0.028
293.3 0.042
5 2 Find the top speed in mph at STP for the Indycar:
5 3 Find the top speed for the Indycar in Denver where the air temp is 90 deg F and barometric pressure is 23.3 in Hg.
5 4 Part A. The pitot tube delta pressure reading at end of straight (EOS) is indicating 35 mbar.
What is the indicated air speed (and therefore theoretical ground speed) in mph (at sea level STP) if the pitot and ground speed usually agree?
Part B. The indicated ground speed however is 174.0 mph and the yaw probe is indicating a yaw of 0.29 degrees even though the driver is steering dead straight ahead!
What can we deduce?
Do we have a headwind or tailwind?
Is there a crosswind, if so, at what angle of incidence and what is its velocity in mph.
Graph the situation with ground, pitot, wind, and yaw probe vectors. Label for clarity. See example
5 5 This time you have a pitot signal of 20 mbar and the indicated ground speed is 113.7 mph with indicated effective yaw of 2.3 deg.
Graph again and explain what you have this time.
Same questions as above.
5 6 If we could shed 70% of the induced drag for the Indycar's rear wing, what would the new top speed at STP?
RW is 4 ft span x 1.5 ft chord. Wing span efficiency value is 0.89. Lift coefficient of wing itself is 3.50.