There are three types of parasitic drag: form drag
(from blunt, non-lift producing surfaces), interference drag (from mixing air flows) and skin friction.
The total drag coefficient consists of a form drag resistance coefficient--CR, an air resistance coefficient--CA, and a skin friction coefficient--[C.sub.F], equation (3):
The form drag results from wave and wake-making, while the skin friction is due to the tangential shear stress on the ship's hull, caused by the fluid flowing over it.
When the broken fiber immersed in the air flow field, the fiber are principally subjected to the air drag force, the tension force, the gravitational force, turbulence fluctuation force and buoyant force and so on, for the sake of computational simplicity, in the works mentioned above, we only considered the air drag force that the influence of the other forces are neglected, the total air drag is the sum of the friction drag and form drag
due to the velocity difference between air and broken fiber, the air drag can be expressed as, respectively, by the following relations (34-38):
However, form drag
would be increased when the attack angle is too large.
11 gives a typical example in which form drag
coefficient CD for 1.44 x 1.44.
Particles that are non-rigid, flagellated, or otherwise subject to higher-than-expected form drag
because of surface features (e.g., particles overcoated with biomass) will have terminal velocities that are lower than this correlation would predict for the average particle diameter and density.
The researchers also discovered that the most important factor for humans is "form drag
," or how the body's shape affects movements in water.
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