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162 FORCE FIELDS
DYNAMICS
DYNAMICS
FORCE FIELDS 163
Strength
Here, set the strength of the wind.
Direction
This has the same effect as described in the Gravity section above.
Drag Coeff.
When air streams over a body, small eddies will beat against the body’s surfaces,
causing deceleration. The Drag Coeff. parameter denes the strength of this effect.
This decelerating effect is usually minor but occasionally it can have a telling inuence
on the object’s motion.
Impact Coeff.
The Impact Coeff. value determines the strength of the air force that will be exerted
on body surfaces that face the wind. The strength of the impact force is proportional
to the surface area facing the wind and the relative velocity of the body compared
to the wind.
Lift Coeff.
This setting denes the strength of lift.
When an airstream passes over a surface, the air pressure will drop. The faster this
airstream, the lower the pressure. A wing must be shaped so that the airstream will
pass over one wing surface more quickly than over the other wing surface. This will
create a pressure gradient, causing the wing to experience a lifting force.
If you were to hold out a piece of paper and blow along its edge, the airstream would
create lift on the paper, causing the paper to follow the direction of the airstream.
A real-world example of lift.
Blow across a hanging piece of
paper and the airstream will
create a lift force that will raise
the paper into line with the
airstream.