Knudsen number
E415503
The Knudsen number is a dimensionless quantity in fluid dynamics that compares a gas’s molecular mean free path to a characteristic physical length scale, indicating whether continuum or rarefied flow models are appropriate.
All labels observed (1)
| Label | Occurrences |
|---|---|
| Knudsen number canonical | 2 |
How this entity was disambiguated
This entity first appeared as the object of triple T4119141 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
NED1
Entity disambiguation (via context triple)
gpt-5-mini-2025-08-07
Target entity: Knudsen number Context triple: [Mach number, relatedConcept, Knudsen number]
-
A.
Knudsen
Knudsen is a Danish-origin surname borne by various notable individuals in fields such as industry, science, and the arts.
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B.
Chandrasekhar number
The Chandrasekhar number is a dimensionless quantity in magnetohydrodynamics that measures the relative importance of magnetic forces compared to viscous forces in a conducting fluid.
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C.
Stokes–Einstein relation
The Stokes–Einstein relation is a fundamental equation in statistical physics that links the diffusion coefficient of a particle in a fluid to its size, the fluid’s viscosity, and temperature.
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D.
Kapitza resistance
Kapitza resistance is the thermal boundary resistance that occurs at the interface between a solid and liquid helium, causing a temperature discontinuity when heat flows across the boundary.
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E.
Stokes' law
Stokes' law is a fundamental equation in fluid dynamics that describes the drag force experienced by small spherical particles moving slowly through a viscous fluid.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
NED2
Entity disambiguation (via description)
gpt-5-mini-2025-08-07
Target entity: Knudsen number Target entity description: The Knudsen number is a dimensionless quantity in fluid dynamics that compares a gas’s molecular mean free path to a characteristic physical length scale, indicating whether continuum or rarefied flow models are appropriate.
-
A.
Knudsen
Knudsen is a Danish-origin surname borne by various notable individuals in fields such as industry, science, and the arts.
-
B.
Chandrasekhar number
The Chandrasekhar number is a dimensionless quantity in magnetohydrodynamics that measures the relative importance of magnetic forces compared to viscous forces in a conducting fluid.
-
C.
Stokes–Einstein relation
The Stokes–Einstein relation is a fundamental equation in statistical physics that links the diffusion coefficient of a particle in a fluid to its size, the fluid’s viscosity, and temperature.
-
D.
Kapitza resistance
Kapitza resistance is the thermal boundary resistance that occurs at the interface between a solid and liquid helium, causing a temperature discontinuity when heat flows across the boundary.
-
E.
Stokes' law
Stokes' law is a fundamental equation in fluid dynamics that describes the drag force experienced by small spherical particles moving slowly through a viscous fluid.
- F. None of above. chosen
Statements (49)
| Predicate | Object |
|---|---|
| instanceOf |
dimensionless quantity
ⓘ
nondimensional number in fluid dynamics ⓘ similarity parameter ⓘ |
| appliesTo |
gas flows around spacecraft
ⓘ
gas flows in microchannels ⓘ gas flows in porous media ⓘ gas flows in vacuum systems ⓘ |
| category |
dimensionless numbers in fluid mechanics
ⓘ
gas dynamics ⓘ |
| compares |
characteristic physical length scale
ⓘ
molecular mean free path ⓘ |
| definition | ratio of molecular mean free path to a characteristic length scale ⓘ |
| dependsOn |
gas density
ⓘ
gas temperature ⓘ molecular collision cross-section ⓘ |
| dimension | dimensionless ⓘ |
| field |
aerodynamics
ⓘ
fluid dynamics ⓘ microfluidics ⓘ rareified gas dynamics ⓘ vacuum technology ⓘ |
| formula | Kn = λ / L ⓘ |
| hasParameter |
characteristic length L
ⓘ
molecular mean free path λ ⓘ |
| indicates | degree of gas rarefaction ⓘ |
| influences |
boundary conditions at solid surfaces
ⓘ
choice between continuum and kinetic theory descriptions ⓘ validity of no-slip boundary condition ⓘ |
| namedAfter | Martin Knudsen ⓘ |
| relatedTo |
Boltzmann equation
ⓘ
Navier–Stokes equations ⓘ continuum flow ⓘ continuum hypothesis ⓘ free molecular flow ⓘ mean free path ⓘ slip flow ⓘ transitional flow ⓘ |
| symbol | Kn ⓘ |
| typicalRange |
0.001 ≤ Kn ≤ 0.1 slip flow regime
ⓘ
0.1 < Kn < 10 transitional flow regime ⓘ Kn < 0.001 continuum flow regime ⓘ Kn ≥ 10 free molecular flow regime ⓘ |
| usedFor |
assessing need for rarefied gas models
ⓘ
assessing validity of continuum flow models ⓘ classifying flow regimes ⓘ modeling gas flows in micro- and nano-scale devices ⓘ modeling high-altitude and space vehicle aerodynamics ⓘ modeling vacuum system flows ⓘ selecting appropriate numerical methods for gas flows ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Input
Subject: Knudsen number Description of subject: The Knudsen number is a dimensionless quantity in fluid dynamics that compares a gas’s molecular mean free path to a characteristic physical length scale, indicating whether continuum or rarefied flow models are appropriate.
Referenced by (2)
Full triples — surface form annotated when it differs from this entity's canonical label.