Task: Instance Description Understanding (ontology: Earth_Environment/SWEET)

Which of the following definitions best describes the instance 'reynolds number'?

A. The volume of water released from or taken into storage per unit volume of the porous medium per unit change in head.
B. The ratio of a region's total precipitation to its external precipitation originating as evaporation from the oceans as opposed to evapotranspiration from the land.
C. The dimensionless ratio of the inertial force (∼U2/L) to the viscous force (∼ νU/L2) in the Navier–Stokes equations, where U is a characteristic velocity, L is a characteristic length, and ν is the kinematic viscosity of the fluid; thus, Re=ULv. the instance is of great importance in the theory of hydrodynamic stability and the origin of turbulence. The inertia force generates vortex stretching and nonlinear interactions and hence creates randomness. Turbulence occurs when the inertia term dominates the viscous term, that is, when the instance is large. For many engineering flows, turbulence occurs when Re > Rec, where the critical the instance is roughly Rec = 2100.
D. A relationship between the advective and diffusive components of solute transport expressed as the ratio of the product of the average interstitial velocity, times the characteristic length, divided by the coefficient of molecular diffusion; small values indicate diffusion dominance, large values indicate advection dominance.

Answer: The dimensionless ratio of the inertial force (∼U2/L) to the viscous force (∼ νU/L2) in the Navier–Stokes equations, where U is a characteristic velocity, L is a characteristic length, and ν is the kinematic viscosity of the fluid; thus, Re=ULv. the instance is of great importance in the theory of hydrodynamic stability and the origin of turbulence. The inertia force generates vortex stretching and nonlinear interactions and hence creates randomness. Turbulence occurs when the inertia term dominates the viscous term, that is, when the instance is large. For many engineering flows, turbulence occurs when Re > Rec, where the critical the instance is roughly Rec = 2100.