# Knudsen Number Calculator

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## Knudsen Number Calculator

Knudsen Number Calculator is a tool that is used to find the molecular effect of the fluid or gases by the ratio of the mean free path and physical length scale.

## What is Knudsen's Number?

The Knudsen number (Kn) is a dimensionless quantity used to determine the relative importance of molecular effects in a gas or fluid flow. It is stated as the ratio of the molecule’s mean free path and the system’s characteristic length scale. The mean free path is the average distance a molecule travels between collisions while the characteristic length scale represents the relevant dimensions of the system.

The Knudsen number provides insights into the behavior of gases and fluids particularly when the size of the system is comparable to or smaller than the mean free path. The molecular interactions or collisions become significant and influence the overall flow dynamics.

## The formula of Knudsen Number

The mathematical formula of the Knudsen number is stated as.

Kn = λ / L

Where,

• Kn = Knudsen number of the fluid
• λ = mean path of molecules
• L = characteristic length scale of the fluid

## How to find Knudsen's Number?

Example 1:

Determine the Knudsen number of the fluids if L = 5 and λ = 150.

Solution:

Step 1:

Write the data carefully.

L = 5, λ = 150, a =?

Formula:

Kn = λ / L

Step 2:

Put the all values in the above formula and simplify carefully.

L = 5 and λ = 150

Kn = λ / L

Kn = 150/5

Kn = 30

Example 2:

Determine the “L” if kn = 30, and λ = 150.

Solution:

Step 1:

Write the data carefully.

Kn = 30, λ = 150, L =?

Formula:

L = λ / kn

Step 2:

Put the all values in the above formula and simplify carefully.

Kn = 30, λ = 150

L = λ / kn

L = 150/30

L = 5

Example 3:

Determine the “λ” if L = 125 and kn = 5.

Solution:

Step 1:

Write the data carefully.

L = 125, kn = 5, λ =?

Formula:

λ = L × kn

Step 2:

Put the all values in the above formula and simplify carefully.

L = 125, kn = 5

λ = L × kn

λ = 125 × 5

λ = 625