Rossby number


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Rossby number

(ross -bee) Symbol: R 0. The ratio of the rotation period P to the turnover time τc of a convective cell in a star's interior or a planetary atmosphere; τc is the time required for hot gas to rise from the bottom to the top of a convective cell and then fall back as it cools. The Rossby number is a measure of the efficiency of a star's dynamo (which ‘drives' its activity), smaller values of R 0 indicating a greater influence of rotation upon convection, and therefore higher activity, irrespective of the surface temperature of the star.

Rossby number

[′rȯs·bē ‚nəm·bər]
(fluid mechanics)
The nondimensional ratio of the inertial force to the Coriolis force for a given flow of a rotating fluid, given as R0= U/fL, where U is a characteristic velocity, f the Coriolis parameter (or, if the system is cylindrical rather than spherical, twice the system's rotation rate), and L a characteristic length.
References in periodicals archive ?
Provided the instructor possesses the requisite background knowledge, the demonstrations on the DIYnamics table can be directly adapted to this level by replacing appeals to the influence of rotation generally to specific concepts such as solid-body rotation, the Coriolis parameter, and the Rossby number.
The quasi-geostrophic fluid is an important model in geophysical fluid dynamics, they are special cases of the general quasi-geostrophic approximations for atmospheric and oceanic fluid flow with the small local Rossby number which ensures the validity of the geostrophic balance between the pressure gradient and the Coriolis force.
[21] that we approach the limit of applicability of the quasi-geostrophic approximation by increasing the spectral resolution in the model to T63, because the Rossby number on the smallest resolved scale becomes comparable to unity.
Higher spinneret speeds can produce fibers with a narrower diameter distribution but much thicker fibers due to the increase in the Rossby number [13].
where [c.sub.0] is a constant and the phase velocity of linear long- wave in shear flow; [epsilon] is dimensionless Rossby number [epsilon] [much less than] 1 and characterizes the strength of the nonlinearity; and [bar.[psi]] is disturbed stream function.
In these model experiments various combinations of Rossby number (Ro=U/fL) and Reynolds number (Re=UL/v) were tried (here U is the inflow velocity, f is the rotation rate, L is the horizontal scale of the basin, and vis the molecular viscosity).
The authors concluded that the westward penetration of the LC intensifies as the Rossby number and Ekman number (Ek=v/f[L.sup.2]) decrease.
Their results show that the northward penetration length of the loop is proportional to a parameter called penetration Rossby number (Rp=[(2QLe/[ohm][alpha]).sup.1/4]/L where Q is the inflow volume transport, Le is the equivalent length of the approaching channel, [ohm] is the angular velocity of the table, [alpha] is the bottom slope, and L is the distance between the inlet and the outlet.
Thus, the flow is controlled by the following non-dimensional parameters: the Rossby number Ro = U/fL = g'H/[f.sup.2][L.sup.2], which is the ratio of the inertial force to the Coriolis force; the Ekman number Ek = [v.sub.1]/f[L.sup.2] = [v.sub.z]/f[H.sup.2], which is the ratio of the viscous force to the Coriolis force; and the Prandtl number Pr = v/[kappa], which is the ratio of the viscosity to the diffusivity, where v is a coefficient of kinematic viscosity and [kappa] is a coefficient of diffusivity.
The external forcing parameter (q), as well as the Rossby number (Ro), had values of the order of [10.sup.-3], and the horizontal Ekman number (Ek) was of the order of [10.sup.-6] for both the model and the Gulf.
In laboratory tests, the Rossby number was set between 1x[l0.sup.-4] <Ro<2000x[10.sup.-4], and the horizontal Ekman number varied between 0 * 3x[10.sup.-6] <Ek<130x[l0.sup.-6].