Knudsen Number Calculator
Calculate Knudsen Number (Kn) to classify gas flow regimes—whether continuum, slip, transitional, or free molecular. This tool is essential for fluid dynamics, microfluidics, vacuum systems, and aerospace engineering.
What is the Knudsen Number?
The Knudsen Number (Kn) is a dimensionless number defined as the ratio of the molecular mean free path (λ) to a characteristic length scale (L), typically the diameter of a pipe or channel.
Formula: Kn = λ / L
🛠️ Enter Your Values:
📈 Why Use This Calculator?
This tool helps in quickly identifying the appropriate flow regime, which is crucial for determining whether traditional continuum assumptions hold or rarefied gas dynamics must be applied.
🔍 Common Applications
- Computational Fluid Dynamics (CFD)
- Micro/nanoscale fluid systems (MEMS, microchannels)
- Vacuum and aerospace systems
- Gas flow analysis in semiconductor manufacturing
❓ Frequently Asked Questions
Q: What unit should I use?
Use any unit (meters, micrometers, etc.) as long as both λ and L are in the same unit.
Q: What does a high Knudsen Number indicate?
A high Kn (>10) means gas molecules travel long distances without collisions, indicating a molecular flow where continuum assumptions fail.
Q: Can this be used for microfluidic devices?
Absolutely. It’s especially useful for evaluating rarefied flow effects in small-scale fluid systems.
💡 Final Note
Bookmark this page and use our Knudsen Number Calculator whenever you’re working with flow modeling, vacuum science, or rarefied gas research. It’s quick, precise, and essential for reliable fluid mechanics analysis.