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A whirlpool is a body of rotating water produced by opposing currents or a current running into an obstacle. [ 1 ] [ clarification needed ] Small whirlpools form when a bath or a sink is draining. More powerful ones formed in seas or oceans may be called maelstroms ( / ˈ m eɪ l s t r ɒ m , - r ə m / MAYL -strom, -strəm ).
In general, vortex lines (in particular, the axis line) are either closed loops or end at the boundary of the fluid. A whirlpool is an example of the latter, namely a vortex in a body of water whose axis ends at the free surface. A vortex tube whose vortex lines are all closed will be a closed torus-like surface.
A vortex street around a cylinder. This can occur around cylinders and spheres, for any fluid, cylinder size and fluid speed, provided that the flow has a Reynolds number in the range ~40 to ~1000. [1] In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime. [2]
When considered in the context of microrobotics and nanorobotics, size is the factor of interest when performing scale analysis. Scale analysis of the Strouhal number allows for analysis of the relationship between mass and inertial forces as both change with respect to size.
A mesoscale convective vortex (MCV) is a low-pressure center within a mesoscale convective system (MCS) that pulls winds into a circling pattern, or vortex. With a core only 30 to 60 mi (48 to 97 km) wide and 1 to 3 mi (1.6 to 4.8 km) deep, an MCV is often overlooked in standard surface observations . [ 7 ]
The Rankine vortex is a simple mathematical model of a vortex in a viscous fluid. It is named after its discoverer, William John Macquorn Rankine. The vortices observed in nature are usually modelled with an irrotational (potential or free) vortex. However, in a potential vortex, the velocity becomes infinite at the vortex center.
Vortex shedding as winds pass Heard Island (bottom left) in the southern Indian Ocean resulted in this Kármán vortex street in the clouds In fluid dynamics , vortex shedding is an oscillating flow that takes place when a fluid such as air or water flows past a bluff (as opposed to streamlined) body at certain velocities, depending on the size ...
A turbulent flow is a flow regime in fluid dynamics where fluid velocity varies significantly and irregularly in both position and time. [3] Furthermore, a coherent structure is defined as a turbulent flow whose vorticity expression, which is usually stochastic, contains orderly components that can be described as being instantaneously coherent over the spatial extent of the flow structure.