Table 1.

Glossary

Term	Definition
Reynolds number (Re)	A nondimensional parameter often used to characterize flow regimes. Re represents the ratio between inertial and viscous forces, and is often used to distinguish between laminar and turbulent flow. Re is defined as follows: $\mathrm{Re}=\left(\rho \cdot l\cdot u\right)/\mu$, where ρ is the density of the fluid (in kilograms per cubic meter), l is the characteristic length of the flow field (in meters), u is flow speed (in meters per second), and μ is dynamic viscosity (in newton⋅second per square meter). When Re is small (Re < 1), viscous forces dominate, and the flow is stable. As Re increases, inertial forces become more important. The flow becomes less stable and turbulence is likely to develop (usually at ∼Re > 105). Re is used for dimensional analysis and for dynamic scaling.
Dynamic scaling	When comparing two flow scenarios of a fully submerged body, the two regimes will be hydrodynamically identical if the nondimensional parameters (Re) are identical. It is possible to investigate the flow field generated by a small body size by using a large body size while simultaneously increasing the viscosity (or decreasing flow speed) and keeping the nondimensional parameters (Re) unchanged.
Dynamically scaled size	The equivalent length (l′) of a solid body in a dynamic-scaling experiment is obtained by keeping the Re constant. Dynamically scaled size is hereafter defined as follows: $l\prime =l\left(u_1{\mu }_2/u_2{\mu }_1\right)$, where l is the real length of the body, u1 and μ1 are flow speed and viscosity under nonmanipulated conditions, and u2 and μ2 are flow speed and viscosity under manipulated conditions. For example, under conditions of a twofold increase in fluid viscosity and constant flow speed, the dynamically scaled size of a 10-mm solid body decreases by twofold to 5 mm (Fig. 3).