hydraulic radii

Noun

hydraulic radius (plural hydraulic radii)

1. (surface science) For a porous material, the ratio of porosity (ratio of volume of interstitial space filled with fluid to volume of material) to specific surface area (ratio of surface area in contact with fluid to volume of material); for a pipe or channel, the ratio of cross-sectional area to wetted perimeter.
   • The hydraulic radius is found from the definition Rₕ = ([volume of (interstitial) pore space filled with fluid]/[surface area of (interstitial) pore apace in contact with fluid]) = (porosity (ε₀)/specific surface area (Sᵥ)), where both ε₀ and Sᵥ are practical and experimentally measurable...1998, Robert Tijssen, “2: The Mechanisms and Importance of Zone-Spreading”, in Elena Katz, Roy Eksteen, Peter Schoenmakers, Neil Miller, editors, Handbook of HPLC, Marcel Decker, page 79