Game Development Reference
In-Depth Information
Drag coefficient is also influenced by whether a shape is two- or three-dimensional.
Table 5-3 shows drag coefficients for a Reynolds number of 1.0e+5 for some typical three-
dimensional shapes. The drag coefficient for a three-dimensional shape is less than that for the
corresponding two-dimensional shape. For example, the drag coefficient for a three-dimensional
hollow half-sphere with the concave side facing the air flow is 1.4, whereas the drag coefficient
for the corresponding two-dimensional hollow half-cylinder is 2.3.
Table 5-3.
Drag Coefficients of Three-Dimensional Shapes (Re = 1.0e+5)
Shape
Picture
C
D
Square flat plate
1.17
Cube
1.05-1.07
Rotated cube
0.8-0.81
Solid hemisphere
0.42
60-degree cone
0.5
Sphere
0.4-0.47
2:1 Ellipsoid
0.27
Hollow hemisphere
1.4
Hollow hemisphere
0.38-0.4
We have seen that the value of the drag coefficient is a function of Reynolds number. It
would simplify the implementation of drag effects into the projectile trajectory model, however,
if the drag coefficient could be assumed to be a constant. For a certain range of Reynolds
number, the drag coefficient for a sphere is more or less constant. Depending on how much
accuracy you want to build into your game programming projectile simulation, it might be
