Assuming all bodies have the same cross-sectional area and are in motion, place these bodies in order of decreasing pressure drag.The correct answer is:
Refer to figure.
Total Drag is sub-divided into two main types:
Parasite Drag - independent of lift generation, and
Induced Drag - the result of lift generation.
Parasite drag is further sub-divided into:
- Skin Friction Drag
- Form (Pressure) Drag, and
- Interference Drag
NOTE: Skin Friction and Form Drag are together known as PROFILE DRAG.
Form drag is produced whenever the streamline airflow passing over an aircraft separates from the surface and becomes turbulent. An example of extreme form drag is the effect of a flat plate placed at right angles to the airflow.
The pressure immediately in front of the plate is above atmospheric, whilst the pressure behind the plate is below atmospheric. This results in a sucking effect behind the plate and the formation of vortices. The more rapidly the airflow changes direction, the greater the pressure gradient, the earlier the separation, and the higher the form drag.
Changing the shape, or streamline, of a given object reduces drag by delaying the point at which the airflow separates.
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