With some exceptions, an Employee is covered by the HCSO if the Employee works for an Employer covered by the HCSO and: 1  Is entitled to be paid the minimum wage; 2  Has been employed by the Employer for at least 90 calendar days; and. 3  Works at least 8 hours per week in San Francisco.
Vortex ring. Spark photography image of a vortex ring in flight. A vortex ring, also called a toroidal vortex, is a torus-shaped vortex in a fluid or gas; that is, a region where the fluid mostly spins around an imaginary axis line that forms a closed loop. The dominant flow in a vortex ring is said to be toroidal, more precisely poloidal.
In fluid dynamics, a vortex is a region in fluid where the flow revolves around an axis line, which may be straight or curved. Vortices are formed in stirred fluids, and may be observed in smoke rings, whirlpools in the wake of boat, or the winds surrounding a tornado or dust devil. Vortices are a major component of turbulent flow. The distribution of velocity, vorticity, as well as the concept of circulation are used to characterize vortices. In most vortices, the fluid flow velocity is greates