Jim Hall’s Chaparral 2F sports-racing cars in the 1960s pioneered use of airfoils mounted above the rear suspension to enhance stability and improve braking performance. The airfoil was effectively 6 ft wide (span) and had a 1-ft chord. Its angle of attack was variable between 0° and −12°. Assume lift and drag coefficient data are given by curves in Fig. 9.17. Consider a car speed of 120 mph on a calm day. For an airfoil deflection of 12° down, calculate (a) the maximum downward force and (b) the maximum increase in deceleration force produced by the airfoil.
Jim Hall’s Chaparral 2F sports-racing cars in the 1960s pioneered use of airfoils mounted above the rear suspension to enhance stability and improve braking performance. The airfoil was effectively 6 ft wide (span) and had a 1-ft chord. Its angle of attack was variable between 0° and −12°. Assume lift and drag coefficient data are given by curves in Fig. 9.17. Consider a car speed of 120 mph on a calm day. For an airfoil deflection of 12° down, calculate (a) the maximum downward force and (b) the maximum increase in deceleration force produced by the airfoil.
Jim Hall’s Chaparral 2F sports-racing cars in the 1960s pioneered use of airfoils mounted above the rear suspension to enhance stability and improve braking performance. The airfoil was effectively 6 ft wide (span) and had a 1-ft chord. Its angle of attack was variable between 0° and −12°. Assume lift and drag coefficient data are given by curves in Fig. 9.17. Consider a car speed of 120 mph on a calm day. For an airfoil deflection of 12° down, calculate (a) the maximum downward force and (b) the maximum increase in deceleration force produced by the airfoil.
Solve Parts A-C and label Them
QUESTION: Suppose you buy a 3 x 7-ft sheet of plywood and put it on your roof rack. You drive home at 45 mi/h.
Part A - If the board is perfectly aligned with the airflow, how thick is the boundary layer at the end of the board?
Part B - Estimate the drag on the sheet of plywood if the boundary layer remains laminar?
Part C - Estimate the drag on the sheet of plywood if the boundary layer is turbulent (assume the wood is smooth) and compare the result to that of the laminar boundary layer case.
HINT - 3 X 7-ft sheet of plywood and put it on your roof rack. You drive home at 45 mi/h.
The Antonov An-225 is the heaviest aircraft ever built, with a maximum takeoff weight of 640 metric tonnes. It also has the largest wingspan of any aircraft in operational service.
Sea level standard day (sls) conditions for calculations are 15°C; 101.3kPa
Rotate speed (Vr) at takeoff (sls):
Vr = 154 kts = 1.2×Vmin
(1 kt = 0.514 m/s)
Cruise Engine Thrust :
a) Calculate the lift coefficient for a standard day takeoff
b) Calculate the drag coefficient at cruis
Fcruise = 0.85 Fmax
Engine maximum thrust:
Factual,max = Fsls,max×δ θ½
δ = Pactual/Pref; and
θ = Tref/Tactual
a)What is the impact of increasing Reynolds number on skin friction and pressure drags over an airfoil? What can be happened for separation in this case?
b) What is an adverse pressure gradient and where does it occur on an airfoil (show that on a sketch)?
c) Why lift-to-drag ratio is an important parameter for an aircraft?
d)How can changing in altitude affect the aircraft power required, PR? Show thatmathematically and graphically?
Chapter 9 Solutions
Fox and McDonald's Introduction to Fluid Mechanics
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