Overview
The Real Gas feature in Luminary Cloud enables accurate simulation of fluid behavior in extreme conditions where standard gas assumptions break down.
Luminary Cloud offers two approaches for real gas calculations:
Method 1: CoolProp Library
What it is: An industry-standard thermodynamic database containing experimentally validated properties for over 100 pure fluids and mixtures.
Advantages:
Validated against extensive experimental data
Covers 100+ fluids (air, nitrogen, oxygen, refrigerants, cryogenic liquids)
Handles complex physics near saturation and critical points
Automatically generates accurate lookup tables
Works reliably across wide pressure and temperature ranges
Available Fluids Include:
Common industrial gases: Air, Nitrogen, Oxygen, Argon, Carbon Dioxide
Hydrocarbons: Methane, Ethane, Propane, Butane
Refrigerants: R22, R134a, R404A, R410A, R507A, and many others
Cryogenic fluids: Ammonia, Hydrogen, Helium, Water vapor
Specialty gases: Sulfur dioxide, Xenon, and more
Method 2: Polynomial Formula (Custom Approach)
What it is: A flexible mathematical formula (NASA 7-coefficient polynomial) that lets you define custom thermodynamic properties tailored to your specific fluid or research data.
Advantages:
Fully customizable to your fluid or mixture
Lightweight and computationally efficient
Perfect for proprietary gas formulations
Compatible with published research coefficients
Narrow focus on relevant temperature ranges
How it works: You specify how specific heat (cp) varies with temperature using a proven polynomial formula:
cp/R = a₁/T² + a₂/T + a₃ + a₄·T + a₅·T² + a₆·T³ + a₇·T⁴
How to Use Real Gas in Your Simulation
Step-by-step
Step 1: Access material properties
In the simulation tree (left panel), expand Materials.
Select the fluid material you want to configure.
If you do not have one yet, create a new fluid material.
Confirm the Material Properties panel is open on the right.
Step 2: Switch the density relationship to Real Gas
Expand Definitions (if it is collapsed).
Find Density Relationship.
Select Real Gas.
Ideal Gas
Real Gas
Constant Density
Constant Density with Energy
Step 3: Choose the real gas method
After selecting Real Gas, you will see Real Gas Method.
Option A: CoolProp (recommended)
Set Real Gas Method to CoolProp Library.
Choose a fluid in the Gas dropdown.
Default: Air
Examples: Nitrogen, Oxygen, R134a, Ammonia
Set the operating range.
Pressure range: Min and Max pressure expected in the simulation
Temperature range: Min and Max temperature expected in the simulation
Use a 10 to 20 percent margin beyond expected conditions to avoid extrapolation.
Optional: adjust table resolution.
Pressure points
Default: 1000
Faster setup: 500 to 700
Higher accuracy: 1200 to 1500
Temperature points
Default: 200
Faster setup: 100 to 150
Higher accuracy: 250 to 300
Option B: Custom polynomial
Set Real Gas Method to Custom Polynomial.
Enter Molecular Weight.
Default for air: 28.96 g/mol
Set the valid Minimum Temperature and Maximum Temperature for the coefficients.
Use a narrow, coefficient-specific range for best accuracy.
Enter polynomial coefficients (a1 through a7) and integration constants (b1 and b2).
Sources: NASA databases, research publications, thermodynamic software exports
Step 4: Configure the thermal conductivity model
Thermal conductivity affects heat diffusion, temperature profiles, and wall heat flux.
Option A: Prescribed Prandtl number
Select Prescribed Prandtl Number in the Thermal Conductivity Model dropdown.
Enter the Prandtl number for the fluid.
Most gases: about 0.7
Water: about 5 to 7
Click Save.
The system computes thermal conductivity from viscosity and specific heat using the Prandtl number.
Option B: Constant thermal conductivity
Select Constant Thermal Conductivity.
Enter a thermal conductivity value.
Click Save.
Option C: Temperature-dependent table
Select Temperature-Dependent Table.
Upload or import a 2-column table: Temperature to Thermal Conductivity.
Confirm the table covers the full simulation temperature range.
Click Save.
Use at least 3 to 5 points.
Sort temperatures in ascending order.
Extend 10 to 20 percent beyond expected operating temperatures.
Step 5: Configure the dynamic viscosity model
Dynamic viscosity controls friction within the fluid and affects drag, heat transfer, and convergence.
Option A: Sutherland's Law
Select Sutherland's Law in the Dynamic Viscosity Model dropdown.
Enter:
Reference Viscosity
Reference Temperature
Sutherland Constant
Reference values are fluid dependent.
Option B: Temperature-dependent table
Select Temperature-Dependent Table.
Provide a viscosity table.
Use at least 3 to 5 points.
Sort temperatures in ascending order.
Extend 10 to 20 percent beyond expected operating temperatures.
Step 6: Save and run
Click Save to apply settings.
Continue normal simulation setup.
Start the simulation.
Real gas property tables are generated automatically on first run.
Subsequent runs reuse cached tables.
How to Verify Real Gas is Working Correctly
Check 1: Table Ranges
Make sure the table ranges cover the minimum static pressure and temperature and the maximum total pressure and temperature
Check 2: Sensitivity of the Results to Table Resolution
Run the same simulation with double the number of temperatures and pressures and see if it affects the results