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Eddy (fluid Dynamics)
In fluid dynamics, an eddy is the swirling of a fluid and the reverse current (water), current created when the fluid is in a Turbulence, turbulent flow regime. The moving fluid creates a space devoid of downstream-flowing fluid on the downstream side of the object. Fluid behind the obstacle flows into the void creating a swirl of fluid on each edge of the obstacle, followed by a short reverse flow of fluid behind the obstacle flowing upstream, toward the back of the obstacle. This phenomenon is naturally observed behind large emergent rocks in swift-flowing rivers. An eddy is a movement of fluid that deviates from the general flow of the fluid. An example for an eddy is a vortex which produces such deviation. However, there are other types of eddies that are not simple vortices. For example, a Rossby wave is an eddy which is an undulation that is a deviation from mean flow, but doesn't have the local closed streamlines of a vortex. Swirl and eddies in engineering The propensity o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the internal frictional force between adjacent layers of fluid that are in relative motion. For instance, when a viscous fluid is forced through a tube, it flows more quickly near the tube's axis than near its walls. Experiments show that some stress (such as a pressure difference between the two ends of the tube) is needed to sustain the flow. This is because a force is required to overcome the friction between the layers of the fluid which are in relative motion. For a tube with a constant rate of flow, the strength of the compensating force is proportional to the fluid's viscosity. In general, viscosity depends on a fluid's state, such as its temperature, pressure, and rate of deformation. However, the dependence on some of these properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Irminger Rings
Irminger Rings (IRs) are mesoscale (15-50 kilometers) ocean eddies that are formed off the West coast of Greenland and travel southwestwards through the Labrador Sea. Most IRs are anti-cyclonic (clockwise in the Northern Hemisphere). There is considerable interest in researching IRs, because they have been hypothesized to influence deep convection in the Labrador sea, and therefore the formation of deep water. Basin overview The Irminger Current (IC) is a branch of the North Atlantic Drift (NAD) that flows westward from Iceland. Because of its Atlantic origins, IC waters are relatively warm and saline compared to the cold, fresh water of the East Greenland Current (EGC) originating from the Greenland Sea. Off the East coast of Greenland, the IC and the EGC meet and "combine" after rounding Cape Farewell to form the heavily stratified current system known as the West Greenland Current (WGC). The top layer of the WGC is 200 meters deep and consists of fresh EGC water. The lay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eddy Diffusion
Eddy diffusion, eddy dispersion, or turbulent diffusion is a process by which substances are mixed in the atmosphere, the ocean or in any fluid system due to eddy motion. In other words, it is mixing that is caused by eddies that can vary in size from subtropical ocean gyres down to the small Kolmogorov microscales. The concept of turbulence or turbulent flow causes eddy diffusion to occur. The theory of eddy diffusion was first developed by Sir Geoffrey Ingram Taylor. In laminar flows, material properties (salt, heat, humidity, aerosols etc.) are mixed by random motion of individual molecules (see molecular diffusion). By a purely probabilistic argument, the net flux of molecules from high concentration area to low concentration area is higher than the flux in the opposite direction. This down-gradient flux equilibrates the concentration profile over time. This phenomenon is called molecular diffusion, and its mathematical aspect is captured by the diffusion equation. In tu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eddy Pumping
Eddy pumping is a component of mesoscale eddy-induced vertical motion. It is a physical mechanism through which vertical motion is created from variations in an eddy's rotational strength. Cyclonic (Anticyclonic) eddies lead primarily to upwelling (downwelling) in the Northern Hemisphere and vice versa in the Southern hemisphere. It is a key mechanism driving biological and biogeochemical processes in the ocean such as algal blooms and the carbon cycle. The mechanism Eddies have a re-stratifying effect, which means they tend to organise the water in layers of different density. These layers are separated by surfaces called isopycnals. The re-stratification of the mixed layer is strongest in regions with large horizontal density gradients, known also as “fronts”, where the geostrophic shear and potential energy provide an energy source from which baroclinic and symmetric instabilities can grow. Below the mixed layer, a region of rapid density change (or pycnocline) separa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vortex
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in the wake of a boat, and the winds surrounding a tropical cyclone, tornado or dust devil. Vortices are a major component of turbulent flow. The distribution of velocity, vorticity (the curl of the flow velocity), as well as the concept of circulation are used to characterise 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. In the absence of external forces, viscous friction within the fluid tends to organise the flow into a collection of irrotational vortices, possibly superimposed to larger-scale flows, including larger-scale vortices. Once formed, vortices can move, stretch, twist, and interact in complex ways. A moving vortex carrie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
