Page |1
Automotive Engineering Exam 2 Questions with 100%
Correct Answers UPDATED!!!
Skin friction - ANSWER i. Viscous drag in the boundary layer
ii. Friction of the fluid (air) against the object's "skin" (auto
body)
Form Drag - ANSWER i. Caused by pressure differential in front
of/behind vehicle as viewed by the air stream.
ii. Keys for reducing: continuous streamlines, avoiding flow
separation.
Contributors to drag - ANSWER Forebody, Afterbody,
Underbody, Skin friction, wheels and wheel wells, drip rails,
window recesses, external mirrors, etc.
Pressure Distribution on a vehicle - ANSWER Figure 4.6 and 4.7
Directional Dependence - ANSWER Sideforce can be significant.
Less so on passenger cars but pronounced effects on trucks and
tractor trailers. The separation region causes a pressure
, Page |2
difference (i.e. form drag) which is why they're so easily blown
over.
Mechanisms of Rolling Resistance - ANSWER a. Energy loss due
to sidewall deflection
b. Energy loss due to tread element deflection
c. Scrubbing in the contact patch
d. Trie slip in longitudinal and lateral directions
e. Road surface deflection/deformation
f. Energy loss due to bumps
g. Air drag on inside and outside of tire
Factors affecting Rx - ANSWER 1. Tire temperature (lower temp
= higher Rx)
2. Tire inflation pressure/load
3. Tire material (High hysteresis bad for rolling resistance)
Match the acronym to the correct description. You can use SAE
J3016 (in "Reading" section on Moodle) or any other reference
you choose.
Automotive Engineering Exam 2 Questions with 100%
Correct Answers UPDATED!!!
Skin friction - ANSWER i. Viscous drag in the boundary layer
ii. Friction of the fluid (air) against the object's "skin" (auto
body)
Form Drag - ANSWER i. Caused by pressure differential in front
of/behind vehicle as viewed by the air stream.
ii. Keys for reducing: continuous streamlines, avoiding flow
separation.
Contributors to drag - ANSWER Forebody, Afterbody,
Underbody, Skin friction, wheels and wheel wells, drip rails,
window recesses, external mirrors, etc.
Pressure Distribution on a vehicle - ANSWER Figure 4.6 and 4.7
Directional Dependence - ANSWER Sideforce can be significant.
Less so on passenger cars but pronounced effects on trucks and
tractor trailers. The separation region causes a pressure
, Page |2
difference (i.e. form drag) which is why they're so easily blown
over.
Mechanisms of Rolling Resistance - ANSWER a. Energy loss due
to sidewall deflection
b. Energy loss due to tread element deflection
c. Scrubbing in the contact patch
d. Trie slip in longitudinal and lateral directions
e. Road surface deflection/deformation
f. Energy loss due to bumps
g. Air drag on inside and outside of tire
Factors affecting Rx - ANSWER 1. Tire temperature (lower temp
= higher Rx)
2. Tire inflation pressure/load
3. Tire material (High hysteresis bad for rolling resistance)
Match the acronym to the correct description. You can use SAE
J3016 (in "Reading" section on Moodle) or any other reference
you choose.
