1.
Oceanography
–
Oceanography, also known as oceanology, is the study of the physical and the biological aspects of the ocean. Paleoceanography studies the history of the oceans in the geologic past, humans first acquired knowledge of the waves and currents of the seas and oceans in pre-historic times. Observations on tides were recorded by Aristotle and Strabo, early exploration of the oceans was primarily for cartography and mainly limited to its surfaces and of the animals that fishermen brought up in nets, though depth soundings by lead line were taken. Although Juan Ponce de León in 1513 first identified the Gulf Stream, Franklin measured water temperatures during several Atlantic crossings and correctly explained the Gulf Streams cause. Franklin and Timothy Folger printed the first map of the Gulf Stream in 1769-1770, information on the currents of the Pacific Ocean was gathered by explorers of the late 18th century, including James Cook and Louis Antoine de Bougainville. James Rennell wrote the first scientific textbooks on oceanography, detailing the current flows of the Atlantic, during a voyage around the Cape of Good Hope in 1777, he mapped the banks and currents at the Lagullas. He was also the first to understand the nature of the intermittent current near the Isles of Scilly, Robert FitzRoy published a four-volume report of the Beagles three voyages. In 1841–1842 Edward Forbes undertook dredging in the Aegean Sea that founded marine ecology, the first superintendent of the United States Naval Observatory, Matthew Fontaine Maury devoted his time to the study of marine meteorology, navigation, and charting prevailing winds and currents. His 1855 textbook Physical Geography of the Sea was one of the first comprehensive oceanography studies, many nations sent oceanographic observations to Maury at the Naval Observatory, where he and his colleagues evaluated the information and distributed the results worldwide. Despite all this, human knowledge of the oceans remained confined to the topmost few fathoms of the water, almost nothing was known of the ocean depths. The Royal Navys efforts to all of the worlds coastlines in the mid-19th century reinforced the vague idea that most of the ocean was very deep. As exploration ignited both popular and scientific interest in the regions and Africa, so too did the mysteries of the unexplored oceans. The seminal event in the founding of the science of oceanography was the 1872-76 Challenger expedition. As the first true oceanographic cruise, this laid the groundwork for an entire academic. In response to a recommendation from the Royal Society, The British Government announced in 1871 an expedition to explore worlds oceans, charles Wyville Thompson and Sir John Murray launched the Challenger expedition. The Challenger, leased from the Royal Navy, was modified for scientific work, under the scientific supervision of Thomson, Challenger travelled nearly 70,000 nautical miles surveying and exploring. On her journey circumnavigating the globe,492 deep sea soundings,133 bottom dredges,151 open water trawls and 263 serial water temperature observations were taken, around 4,700 new species of marine life were discovered. The result was the Report Of The Scientific Results of the Exploring Voyage of H. M. S, Murray, who supervised the publication, described the report as the greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth and sixteenth centuries
2.
Ocean current
–
Depth contours, shoreline configurations, and interactions with other currents influence a currents direction and strength. Therefore ocean currents are primarily horizontal water movements, Ocean currents flow for great distances, and together, create the global conveyor belt which plays a dominant role in determining the climate of many of the Earth’s regions. More specifically, ocean currents influence the temperature of the regions through which they travel, for example, warm currents traveling along more temperate coasts increase the temperature of the area by warming the sea breezes that blow over them. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any region at the same latitude. Another example is Lima, Peru where the climate is cooler than the tropical latitudes in which the area is located, in these wind driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. In addition, the areas of ocean currents move somewhat with the seasons. Deep ocean basins generally have a surface current, in that the eastern equatorward-flowing branch is broad. These western boundary currents are a consequence of the rotation of the Earth, Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation is known as the oceans conveyor belt. These currents, called submarine rivers, flow under the surface of the ocean and are hidden from immediate detection, where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling. Deep ocean currents are currently being researched using a fleet of robots called Argo. The South Equatorial Currents of the Atlantic and Pacific straddle the equator, though the Coriolis effect is weak near the equator, water moving in the currents on either side of the equator is deflected slightly poleward and replaced by deeper water. Thus, equatorial upwelling occurs in these westward flowing equatorial surface currents, upwelling is an important process because this water from within and below the pycnocline is often rich in nutrients and greatly benefits the growth of marine organisms. By contrast, generally poor conditions for growth prevail in most of the tropical ocean because strong layering isolates deep. Ocean currents are measured in sverdrup, where 1 sv is equivalent to a flow rate of 1,000,000 m3 per second. Surface currents are found on the surface of an ocean, and are driven by large scale wind currents and they are directly affected by the wind—the Coriolis effect plays a role in their behaviors. Horizontal and vertical currents also exist below the pycnocline in the deeper waters. The movement of water due to differences in density as a function of water temperature, ripple marks in sediments, scour lines, and the erosion of rocky outcrops on deep-ocean floors are evidence that relatively strong, localized bottom currents exist
3.
Wind
–
Wind is the flow of gases on a large scale. On the surface of the Earth, wind consists of the movement of air. Winds are commonly classified by their scale, their speed, the types of forces that cause them, the regions in which they occur. The strongest observed winds on a planet in the Solar System occur on Neptune, Winds have various aspects, an important one being its velocity, another the density of the gas involved, another its energy content or wind energy. In meteorology, winds are referred to according to their strength. Short bursts of high speed wind are termed gusts, strong winds of intermediate duration are termed squalls. Long-duration winds have various names associated with their strength, such as breeze, gale, storm. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet, within the tropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds, in areas that have variable terrain, mountain, Wind powers the voyages of sailing ships across Earths oceans. Hot air balloons use the wind to take trips, and powered flight uses it to increase lift. Areas of wind caused by various weather phenomena can lead to dangerous situations for aircraft. When winds become strong, trees and man-made structures are damaged or destroyed, Winds can shape landforms, via a variety of aeolian processes such as the formation of fertile soils, such as loess, and by erosion. Wind also affects the spread of wildfires, Winds can disperse seeds from various plants, enabling the survival and dispersal of those plant species, as well as flying insect populations. When combined with temperatures, wind has a negative impact on livestock. Wind affects animals food stores, as well as their hunting, Wind is caused by differences in the atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the pressure area. On a rotating planet, air will also be deflected by the Coriolis effect, globally, the two major driving factors of large-scale wind patterns are the differential heating between the equator and the poles and the rotation of the planet. Outside the tropics and aloft from frictional effects of the surface, near the Earths surface, friction causes the wind to be slower than it would be otherwise
4.
Coriolis force
–
In physics, the Coriolis force is an inertial force that acts on objects that are in motion relative to a rotating reference frame. In a reference frame with clockwise rotation, the acts to the left of the motion of the object. In one with anticlockwise rotation, the acts to the right. Early in the 20th century, the term Coriolis force began to be used in connection with meteorology, deflection of an object due to the Coriolis force is called the Coriolis effect. Newtons laws of motion describe the motion of an object in a frame of reference. When Newtons laws are transformed to a frame of reference. Both forces are proportional to the mass of the object, the Coriolis force is proportional to the rotation rate and the centrifugal force is proportional to its square. The Coriolis force acts in a perpendicular to the rotation axis. The centrifugal force acts outwards in the direction and is proportional to the distance of the body from the axis of the rotating frame. These additional forces are termed inertial forces, fictitious forces or pseudo forces and they allow the application of Newtons laws to a rotating system. They are correction factors that do not exist in a non-accelerating or inertial reference frame, a commonly encountered rotating reference frame is the Earth. The Coriolis effect is caused by the rotation of the Earth, such motions are constrained by the surface of the Earth, so only the horizontal component of the Coriolis force is generally important. This force causes moving objects on the surface of the Earth to be deflected to the right in the Northern Hemisphere, the horizontal deflection effect is greater near the poles, since the effective rotation rate about a local vertical axis is largest there, and smallest at the equator. This effect is responsible for the rotation of large cyclones, riccioli, Grimaldi, and Dechales all described the effect as part of an argument against the heliocentric system of Copernicus. In other words, they argued that the Earths rotation should create the effect, the effect was described in the tidal equations of Pierre-Simon Laplace in 1778. Gaspard-Gustave Coriolis published a paper in 1835 on the yield of machines with rotating parts. That paper considered the forces that are detected in a rotating frame of reference. Coriolis divided these forces into two categories
5.
Vorticity
–
Conceptually, vorticity could be determined by marking the part of continuum in a small neighborhood of the point in question, and watching their relative displacements as they move along the flow. The vorticity vector would be twice the angular velocity vector of those particles relative to their center of mass. This quantity must not be confused with the velocity of the particles relative to some other point. More precisely, the vorticity is a pseudovector field ω→, defined as the curl of the flow velocity u→ vector, the definition can be expressed by the vector analysis formula, ω → ≡ ∇ × u →, where ∇ is the del operator. The vorticity of a flow is always perpendicular to the plane of the flow. The vorticity is related to the flows circulation along a path by the Stokes theorem. Namely, for any infinitesimal surface element C with normal direction n→ and area dA, many phenomena, such as the blowing out of a candle by a puff of air, are more readily explained in terms of vorticity rather than the basic concepts of pressure and velocity. This applies, in particular, to the formation and motion of vortex rings, in a mass of continuum that is rotating like a rigid body, the vorticity is twice the angular velocity vector of that rotation. This is the case, for example, of water in a tank that has been spinning for a while around its vertical axis, the vorticity may be nonzero even when all particles are flowing along straight and parallel pathlines, if there is shear. The vorticity will be zero on the axis, and maximum near the walls, conversely, a flow may have zero vorticity even though its particles travel along curved trajectories. An example is the ideal irrotational vortex, where most particles rotate about some straight axis, another way to visualize vorticity is to imagine that, instantaneously, a tiny part of the continuum becomes solid and the rest of the flow disappears. If that tiny new solid particle is rotating, rather than just moving with the flow, mathematically, the vorticity of a three-dimensional flow is a pseudovector field, usually denoted by ω→, defined as the curl or rotational of the velocity field v→ describing the continuum motion. In Cartesian coordinates, ω → = ∇ × v → = × = In words, the evolution of the vorticity field in time is described by the vorticity equation, which can be derived from the Navier–Stokes equations. This is clearly true in the case of 2-D potential flow, Vorticity is a useful tool to understand how the ideal potential flow solutions can be perturbed to model real flows. In general, the presence of viscosity causes a diffusion of vorticity away from the vortex cores into the flow field. This flow is accounted for by the term in the vorticity transport equation. Thus, in cases of very viscous flows, the vorticity will be diffused throughout the flow field, a vortex line or vorticity line is a line which is everywhere tangent to the local vorticity vector. Vortex lines are defined by the relation d x ω x = d y ω y = d z ω z, a vortex tube is the surface in the continuum formed by all vortex-lines passing through a given closed curve in the continuum
6.
Curl (mathematics)
–
In vector calculus, the curl is a vector operator that describes the infinitesimal rotation of a 3-dimensional vector field. At every point in the field, the curl of that point is represented by a vector, the attributes of this vector characterize the rotation at that point. The direction of the curl is the axis of rotation, as determined by the rule. If the vector represents the flow velocity of a moving fluid. A vector field whose curl is zero is called irrotational, the curl is a form of differentiation for vector fields. The alternative terminology rotor or rotational and alternative notations rot F and ∇ × F are often used for curl F and this is a similar phenomenon as in the 3 dimensional cross product, and the connection is reflected in the notation ∇ × for the curl. The name curl was first suggested by James Clerk Maxwell in 1871, the curl of a vector field F, denoted by curl F, or ∇ × F, or rot F, at a point is defined in terms of its projection onto various lines through the point. As such, the curl operator maps continuously differentiable functions f, ℝ3 → ℝ3 to continuous functions g, in fact, it maps Ck functions in ℝ3 to Ck −1 functions in ℝ3. Implicitly, curl is defined by, ⋅ n ^ = d e f lim A →0 where ∮C F · dr is a line integral along the boundary of the area in question, and | A | is the magnitude of the area. Note that the equation for each component, k can be obtained by exchanging each occurrence of a subscript 1,2,3 in cyclic permutation, 1→2, 2→3, and 3→1. If are the Cartesian coordinates and are the coordinates, then h i =2 +2 +2 is the length of the coordinate vector corresponding to ui. The remaining two components of curl result from cyclic permutation of indices,3,1,2 →1,2,3 →2,3,1. Suppose the vector field describes the velocity field of a fluid flow, if the ball has a rough surface, the fluid flowing past it will make it rotate. The rotation axis points in the direction of the curl of the field at the centre of the ball, and the angular speed of the rotation is half the magnitude of the curl at this point. The notation ∇ × F has its origins in the similarities to the 3-dimensional cross product, such notation involving operators is common in physics and algebra. However, in coordinate systems, such as polar-toroidal coordinates. This expands as follows, i + j + k Although expressed in terms of coordinates, equivalently, = e k ε k l m ∇ l F m where ek are the coordinate vector fields. Equivalently, using the derivative, the curl can be expressed as, ∇ × F = ♯ Here ♭ and ♯ are the musical isomorphisms
7.
Torque
–
Torque, moment, or moment of force is rotational force. Just as a force is a push or a pull. Loosely speaking, torque is a measure of the force on an object such as a bolt or a flywheel. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque that loosens or tightens the nut or bolt, the symbol for torque is typically τ, the lowercase Greek letter tau. When it is called moment of force, it is denoted by M. The SI unit for torque is the newton metre, for more on the units of torque, see Units. This article follows US physics terminology in its use of the word torque, in the UK and in US mechanical engineering, this is called moment of force, usually shortened to moment. In US physics and UK physics terminology these terms are interchangeable, unlike in US mechanical engineering, Torque is defined mathematically as the rate of change of angular momentum of an object. The definition of states that one or both of the angular velocity or the moment of inertia of an object are changing. Moment is the term used for the tendency of one or more applied forces to rotate an object about an axis. For example, a force applied to a shaft causing acceleration, such as a drill bit accelerating from rest. By contrast, a force on a beam produces a moment, but since the angular momentum of the beam is not changing. Similarly with any force couple on an object that has no change to its angular momentum and this article follows the US physics terminology by calling all moments by the term torque, whether or not they cause the angular momentum of an object to change. The concept of torque, also called moment or couple, originated with the studies of Archimedes on levers, the term torque was apparently introduced into English scientific literature by James Thomson, the brother of Lord Kelvin, in 1884. A force applied at an angle to a lever multiplied by its distance from the levers fulcrum is its torque. A force of three newtons applied two metres from the fulcrum, for example, exerts the same torque as a force of one newton applied six metres from the fulcrum. More generally, the torque on a particle can be defined as the product, τ = r × F, where r is the particles position vector relative to the fulcrum. Alternatively, τ = r F ⊥, where F⊥ is the amount of force directed perpendicularly to the position of the particle, any force directed parallel to the particles position vector does not produce a torque
8.
Vortex
–
In fluid dynamics, a vortex is a region in a fluid in which the flow rotates around an axis line, which may be straight or curved. The plural of vortex is either vortices or vortexes, vortices form in stirred fluids, and may be observed in phenomena such as smoke rings, whirlpools in the wake of boat, or the winds surrounding a tornado or dust devil. Vortices are a component of turbulent flow. The distribution of velocity, vorticity, as well as the concept of circulation are used to characterize vortices, in most vortices, the fluid flow velocity is greatest next to its axis and decreases in inverse proportion to the distance from the axis. Once formed, vortices can move, stretch, twist, a moving vortex carries with it some angular and linear momentum, energy, and mass. A key concept in the dynamics of vortices is the vorticity, conceptually, the vorticity could be observed by placing a tiny rough ball at the point in question, free to move with the fluid, and observing how it rotates about its center. The direction of the vorticity vector is defined to be the direction of the axis of rotation of this imaginary ball while its length is twice the angular velocity. The local rotation measured by the vorticity ω → must not be confused with the velocity vector of that portion of the fluid with respect to the external environment or to any fixed axis. In a vortex, in particular, ω → may be opposite to the angular velocity vector of the fluid relative to the vortexs axis. In theory, the u of the particles in a vortex may vary with the distance r from the axis in many ways. Ω → =, r → =, u → = Ω → × r → =, ω → = ∇ × u → = =2 Ω →. In this case the vorticity ω → is zero at any point not on that axis, Ω → =, r → =, u → = Ω → × r → =, ω → = ∇ × u → =0. In the absence of forces, a vortex usually evolves fairly quickly toward the irrotational flow pattern. Irrotational vortices are also called free vortices, for an irrotational vortex, the circulation is zero along any closed contour that does not enclose the vortex axis, and has a fixed value, Γ, for any contour that does enclose the axis once. The tangential component of the velocity is then u θ = Γ2 π r. The angular momentum per unit mass relative to the axis is therefore constant. However, the ideal irrotational vortex flow is not physically realizable, indeed, in real vortices there is always a core region surrounding the axis where the particle velocity stops increasing and then decreases to zero as r goes to zero. Within that region, the flow is no longer irrotational, the vorticity ω → becomes non-zero, the Rankine vortex is a model that assumes a rigid-body rotational flow where r is less than a fixed distance r0, and irrotational flow outside that core regions
![[icon]](/wiki/File:Wiki_letter_w_cropped.svg){kind=small}
