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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.
A vortex tube is the surface in the continuum formed by all vortex lines passing through a given (reducible) closed curve in the continuum. The 'strength' of a vortex tube (also called vortex flux ) [ 11 ] is the integral of the vorticity across a cross-section of the tube, and is the same everywhere along the tube (because vorticity has zero ...
The first source term on the right hand side represents vortex stretching. The equation is valid in the absence of any concentrated torques and line forces for a compressible , Newtonian fluid . In the case of incompressible flow (i.e., low Mach number ) and isotropic fluids, with conservative body forces, the equation simplifies to the ...
The Reynolds number is the ratio of inertial forces to viscous forces within a fluid that is subjected to relative internal movement due to different fluid velocities. A region where these forces change behavior is known as a boundary layer, such as the bounding surface in the interior of a pipe.
For spheres in uniform flow in the Reynolds number range of 8×10 2 < Re < 2×10 5 there co-exist two values of the Strouhal number. The lower frequency is attributed to the large-scale instability of the wake, is independent of the Reynolds number Re and is approximately equal to 0.2. The higher-frequency Strouhal number is caused by small ...
The polar vortex is a gigantic, circular area of cold air high up in the atmosphere that typically spins over the North Pole (as its name suggests).
The Vortex Indicator is a technical indicator invented by Etienne Botes and Douglas Siepman to ... calculate the current true range: ... calculate the current upward ...
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.