hydrodynamic lubrication region

quasi-hydrodynamic lubrication

hydrodynamic control fin

hydrodynamic drag

hydrodynamic test

substantial change of a hydrodynamic quantity

substantial derivative of a hydrodynamic quantity

local change of a hydrodynamic quantity

local derivate of a hydrodynamic quantity

material change of a hydrodynamic quantity

material derivative of a hydrodynamic quantity

arid region

army readiness region

flight information region (FIR)

geostrategic region

strategic region

air defense region (ADR)

depot distribution region

ensure peace and stability in the region

irrotational region

stagnation region

dead region

vorticity region

search and rescue region

simply coherent region

simply connected region

transition region

densely populated (densely-populated) area (region) / territory / country

confusion region

region of interest (ROI)

lubrication

lubrication oil system

hydrostatic feed lubrication