Oceanic Physical-biological Process - Drag

Drag

Drag is the tendency of an object to move in the direction of the flow. The magnitude of drag depends on the current velocity, the shape and size of the organism and the density of the fluid. Drag is a dissipative process which generally results in the generation of heat.

In sea water, drag can be decomposed into two different forms: skin friction and pressure drag.

  1. Skin friction: just like other frictional forces, skin friction is a consequence of the relative movement between the surface of the organisms and its fluid environment. Under conditions of low Re, where viscous forces dominate, the skin friction is apparent and is more important, although it is also present under high Re conditions.
  2. Pressure drag: pressure drag is a result of the pressure difference in front of, and behind, an organism. Incidentally, the shape that has the lowest pressure drag coefficient is a hollow hemisphere oriented in the direction of fluid flow. In the oceanic environment plants and settled animals have bodies that are soft and flexible in order to minimize the effects of pressure drag.

Besides being soft and flexible, organisms have other methods to minimize drag.

  • Smooth skin: dolphins have little tear drops in their skin which traps some water so water flows over the water that is trapped. The skin feels soft and flaky and sheds every two hours. This helps dolphins swim through the sea water at high speed.
  • Shark skin: the surface of shark skin is covered with tiny 'teeth' or dermal denticles. The shape and positioning of these denticles varies across the shark's body, altering the flow of water in a way to minimize form drag.
  • Barracuda skin: Barracuda have hundreds of skin conduits which force the fluid flows to follow the parallel tubes and become laminar. Again, this arrangement decreases water drag.

Read more about this topic:  Oceanic Physical-biological Process

Other articles related to "drag":

Beetle Restoration - Motorsport - Drag Racing
... The Beetle is widely used in drag racing its rearward (RR layout) weight distribution keeps the weight over the rear wheels, maximizing grip off the starting line ... The car's weight is reduced for a full competition drag Beetle, further improving the grip and also the power-to-weight ratio ...
The Way Out (Drag Album) - Background
... Matt Murphy and fellow Powderfinger member John Collins on bass, Drag began performing around Brisbane and its surrounding areas ... Middleton had intended recording some of the Drag songs in the hiatus time, but when the opportunity was offered by Paul Piticco, Powderfinger's manager and ... Drag then recorded The Way Out in early 2005 at a recording studio in the Northern New South Wales beachside town Byron Bay ...
Aerodynamic Drag
... In aerodynamics, aerodynamic drag is the fluid drag force that acts on any moving solid body in the direction of the fluid freestream flow ... From the body's perspective (near-field approach), the drag comes from forces due to pressure distributions over the body surface, symbolized, and forces due to skin friction, which is a result of viscosity ... perspective (far-field approach), the drag force comes from three natural phenomena shock waves, vortex sheet, and viscosity ...
Lake Geneva Raceway - History - Drag Strip
... The track opened on July 3, 1963 as a drag strip ... The first drag race was won by Fox ... The final drag race was held in 1977, and was won by Fritz Barels ...
Drag, Norway
... Drag (Lule Sami Ájluokta and Northern Sami Áiluokta) is a village in the municipality of Tysfjord in Nordland county, Norway ... Drag is located along Norwegian National Road 827 runs through Drag to a ferry port that connects to the village of Kjøpsvik across the fjord ... Árran, the national Lule Sami Center is located in Drag ...

Famous quotes containing the word drag:

    Our own theological Church, as we know, has scorned and vilified the body till it has seemed almost a reproach and a shame to have one, yet at the same time has credited it with power to drag the soul to perdition.
    Eliza Farnham (1815–1864)

    Executives are like joggers. If you stop a jogger, he goes on running on the spot. If you drag an executive away from his business, he goes on running on the spot, pawing the ground, talking business. He never stops hurtling onwards, making decisions and executing them.
    Jean Baudrillard (b. 1929)

    Dying smokers sense
    Walking towards them through some dappled park
    As if on water that unfocused she
    No match lit up, nor drag ever brought near....
    Philip Larkin (1922–1986)