J. Potvin, G. Peek, and B. Brocato
Saint Louis University
St. Louis, MO 63103, USA
Published in the Journal of Aircraft, 40, No. 2, pp. 370-377, 2003.
Abstract
A new model of the drag force generated by a freely decelerating bluff
body is presented. The model is based, mainly, on the premise that the
wake of an object accelerating downwind in a moving fluid is identical
to that of the same object decelerating in the fluid at rest. After
arguing for the drag of a wind drifter depending only on a power function
of its speed relative to the wind, a Galilean transformation is used to
provide a formula for decelerating body drag of the form FD ~ Vb. The
value of exponent b is dependent on the amount of external force applied
to the body, as well as on its initial and final drag coefficients and
its initial speed. By implication, this exponent depends on the specific
history of the motion. Applications to powered and un-powered vehicles
trailing a parachute or any other high-drag devices are presented and
discussed. The model is also shown to compare favorably with parachute
test drop data.