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Laminar flow over a body occurs when layers of the fluid move smoothly past each other in parallel lines. In nature, this kind of flow is rare. As the fluid flows over an object, it applies frictional forces to the surface of the object which works to impede forward movement of the object; the result is called skin friction drag.
Due to the higher density of sea water (1,030 kg m −3) than air (1.2 kg m −3), the force exerted by the same velocity on an organism is 827 times stronger in the ocean. When waves crash on the shore, the force exerted on littoral organisms can be equivalent to several tons.
Form drag is determined by the cross-sectional shape and area of the body. Skin friction drag (or viscous drag), which is caused by friction between the fluid and the surface of the object. The surface may be the outside of an object, such as a boat hull, or the inside of an object, such as the bore of a pipe.
Munk & Wunsch (1998) estimated that Earth experiences 3.7 TW (0.0073 W/m 2) of tidal heating, of which 95% (3.5 TW or 0.0069 W/m 2) is associated with ocean tides and 5% (0.2 TW or 0.0004 W/m 2) is associated with Earth tides, with 3.2 TW being due to tidal interactions with the Moon and 0.5 TW being due to tidal interactions with the Sun. [3] Egbert & Ray (2001) confirmed that overall ...
In the theory of heat transfer, a thermal boundary layer occurs. A surface can have multiple types of boundary layer simultaneously. The viscous nature of airflow reduces the local velocities on a surface and is responsible for skin friction. The layer of air over the wing's surface that is slowed down or stopped by viscosity, is the boundary ...
The Coulomb friction may take any value from zero up to , and the direction of the frictional force against a surface is opposite to the motion that surface would experience in the absence of friction. Thus, in the static case, the frictional force is exactly what it must be in order to prevent motion between the surfaces; it balances the net ...
A similar process can occur if there is water present in the rock. As the fault begins to slip, this rapid increase in temperature close to the fault causes the water in the pore space to vaporize. As the water vapor expands, it causes the pores along the fault surface to dilate and thereby creates a smoother surface at the fault interface.
Because the air at the surface has near-zero velocity but the air away from the surface is moving, there is a thin boundary layer in which air close to the surface is subjected to a shearing motion. [ 72 ] [ 73 ] The air's viscosity resists the shearing, giving rise to a shear stress at the airfoil's surface called skin friction drag .