Darcy (unit)

A non-SI unit of intrinsic permeability defined through Darcy’s law, equal to approximately 9.869233 times ten to the minus thirteen square metres.

Version

v1 · 2026-09-08 · History

Domain-specific #

4024

Origin domain

porous media measurement

Subdomain

porous media measurement

Aliases

Darcy unit

Core Idea

Permeability is a material property distinct from hydraulic conductivity, the historical definition mixes centimetre-gram-second conventions and viscosity units, and reported darcy values require unit conversion and flow-regime assumptions. The unit is fixed by the permeability that supports a specified volumetric flow through a specified porous cross-section and length under a pressure gradient for a fluid of specified dynamic viscosity. The abstraction is therefore identified by a declared carrier, a transformation or constraint over that carrier, and an invariant that tells an analyst whether the named structure is genuinely present.

Scope of Application

Darcy (unit) belongs to porous media measurement and is useful where the analyst can specify the typed porous media measurement carrier, including objects, relations, parameters, conventions, evidence, boundaries, and comparison targets, then evaluate the homogeneous porous medium and cross-sectional area and length, steady laminar single-phase flow, volumetric flow rate, pressure drop, dynamic viscosity, Darcy-law sign and geometry convention, intrinsic permeability k, definition of one darcy and millidarcy, SI conversion to square metres and distinction from hydraulic conductivity and apparent permeability are explicit.

Clarity

The abstraction clarifies a crowded vocabulary by making the homogeneous porous medium and cross-sectional area and length, steady laminar single-phase flow, volumetric flow rate, pressure drop, dynamic viscosity, Darcy-law sign and geometry convention, intrinsic permeability k, definition of one darcy and millidarcy, SI conversion to square metres and distinction from hydraulic conductivity and apparent permeability are explicit the center of the account. A claim should name the carrier, the governing operation or relation, the applicable assumptions, and the recognition test.

Manages Complexity

Without the abstraction, an analyst must reason directly over many local details: the carrier roles, admissibility assumptions, competing conventions, derived invariants, boundary cases, and proof or validation obligations specific to Darcy (unit). Darcy (unit) compresses them into the roles in the structural signature. That compression permits comparison across instances without erasing the variables that determine validity. It also exposes which details may be varied safely and which are constitutive.

Abstract Reasoning

1. Identify the carrier. State what the elements, states, objects, or observations are: the typed porous media measurement carrier, including objects, relations, parameters, conventions, evidence, boundaries, and comparison targets. Reject examples whose alleged carrier belongs to a different problem. 2. Lock the constitutive rule. Express the homogeneous porous medium and cross-sectional area and length, steady laminar single-phase flow, volumetric flow rate, pressure drop, dynamic viscosity, Darcy-law sign and geometry convention, intrinsic permeability k, definition of one darcy and millidarcy, SI conversion to square metres and distinction from hydraulic conductivity and apparent permeability are explicit independently of one notation or implementation.

Knowledge Transfer

Knowledge transfers strongly among subfields of porous media measurement because they reuse the typed porous media measurement carrier, including objects, relations, parameters, conventions, evidence, boundaries, and comparison targets, The unit is fixed by the permeability that supports a specified volumetric flow through a specified porous cross-section and length under a pressure gradient for a fluid of specified dynamic viscosity., and type the carrier, state every parameter and convention in the definition, test that the homogeneous porous medium and cross-sectional area and length, steady laminar single-phase flow, volumetric flow rate, pressure drop, dynamic viscosity, Darcy-law sign and geometry convention, intrinsic permeability k, definition of one darcy and millidarcy, SI conversion to square metres and distinction from hydraulic conductivity and apparent permeability are explicit, compare the nearest accepted identity, and report counterexamples, uncertainty, and limiting cases.

Relationships to Other Abstractions

Current abstraction Darcy (unit) Domain-specific

Parents (1) — more general patterns this builds on

• Darcy (unit) is a kind of Measurement Prime

  The proposed strict upward parent is prime:measurement.

Hierarchy path (1) — routes to 1 parentless root

• Darcy (unit) → Measurement

Neighborhood in Abstraction Space

Darcy (unit) sits in a sparse region of the domain-specific corpus (70^th percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.

Family — Fluid Flow & Transport (27 abstractions)

Nearest neighbors

• Hydraulic action — 0.85
• Marangoni number — 0.84
• Material derivative — 0.84
• Potential density — 0.84
• Stefan adhesion — 0.84

Computed from structural-signature embeddings · 2026-09-08