PLOT3D variables in EnSight are non-dimensional. They are non-dimensionalized in a somewhat arcane calculation. The density is scaled by the freestream density, the momentum is scaled by the product of the freestream density and the speed of sound, and the Energy is scaled by the product of the freestream density and the speed of sound squared.

For those who don’t want to go through this calculation of dimensioned variables manually and want access to the engineering variables in consistent, user-selected units at a user-selected altitude from a PLOT3D calculation, this script calculates the extended plot3d variables in either SI or English units. This script uses the non-dimensional Plot3D Energy, Density, and Momentum variables in its calculation. This script is assumes Earth atmospheric data. So, it is not valid for calculations on Mars, nor is it valid for calculations in water.

If ‘Energy’, ‘Density’ and ‘Momentum’ all exist then the script will prompt the user for unit type (SI or English) and the altitude and then use a lookup table to find the corresponding variables in consistent units. The code will then calculate a Density_true, Momentum_true, and Energy_true variables (which have consistent units for the user input) and use those to calculate the extended CFD variables.

Click below to download the zipped EnSight Python Script