| 释义 |
vorticity|vɔːˈtɪsɪtɪ|
[f. as prec. + -ity.]
The condition of a fluid, etc., with respect to vortical motion. In mod. use, a vector quantity equal at any given point in a fluid to twice the angular velocity of a small element of fluid about the point.
1888A. B. Bassett Treat. Hydrodynamics I. 75 Let P be any point on the axis of one of these [vortex] filaments, dm the mass of the filament which contains P, ω and dS the molecular rotation and cross section of the filament... Then the quantity ωdS/dm is called the vorticity of the fluid at the point P. 1895Athenæum 23 Nov. 722/2 [Math. Soc.] On the Propagation of Waves upon the Plane Surface separating Two Portions of Fluid of Different Vorticities. 1896Proc. London Math. Soc. XXVII. 14 The component velocities..u and v, are connected with a stream-function Ψ by the relations u = dΨ/dy, v = -dΨ/dx. The vorticity is represented by ½∇2Ψ. 1916H. Lamb Hydrodynamics (ed. 4) iii. 30 The component angular velocities of the rotation being ½ξ, ½η, ½ζ. The vector whose components are ξ, η, ζ may conveniently be called the ‘vorticity’ of the medium at the point (x, y, z). 1938L. M. Milne-Thomson Theoret. Hydrodynamics xix. 511 Either sense of rotation can be obtained according as the bath is filled with the hot or the cold tap, the fluid from one or the other acquiring opposite vorticities as it moves near the boundary. 1958Science 4 Apr. 731/3 On the surface of a fluid, the vorticity may be observed by following a cork marked with a cross... If the arms of the cross do not rotate, the vorticity is zero; if they do rotate, there is vorticity. 1976Nature 1 Apr. 457/1 A motor vehicle or any other projectile in air produces vortices in its wake, but no net vorticity. |