There are aerodynamic forces created by an object moving through

a fluid, which depend on the velocity of the object (or fluid),

the mass and shape of the object, and the viscosity of the fluid.

The Reynolds number is a dimensionless number that expresses the

ratio of inertial (resistant to change or motion) forces to the

viscous (heavy and gluey) forces in the fluid. Thus this equation

can be used to analyze different vortices throughout this site.

"Where NR is the Reynolds number, u is the velocity

of the vortex ring, dh is a characteristic length,

and ν is the kinematic viscosity of air."