A Vortex Lattice Method implemented in Python for use from terminal or from within Python.
Installation:
pip install pyvlm
Terminal Usage:
pyvlm aircraft.json
The above command generates a "aircraft.md" file containing results.
JSON Definition File:
{
"name": "Test Aircraft",
"mach": 0.0,
"sref": 1.358,
"cref": 0.31,
"bref": 4.5,
"xref": 1.175,
"yref": 0.0,
"zref": 0.0,
"surfaces": [
{
"name": "Wing",
"angle": 0.0,
"mirror": true,
"numc": 8,
"cspace": "cosine",
"xpos": 0.875,
"ypos": 0.0,
"zpos": 0.15,
"sections": [
{
"xpos": 0.0,
"ypos": 0.0,
"zpos": 0.0,
"chord": 0.35,
"angle": 0.0,
"numb": 3,
"bspace": "equal",
"airfoil": "NACA 2412",
"noload": true
},
{
"xpos": null,
"ypos": 0.21,
"zpos": null,
"chord": 0.35,
"angle": 0.0,
"numb": 5,
"bspace": "semi-cosine",
"airfoil": "NACA 2412"
},
{
"xpos": null,
"ypos": 0.8,
"zpos": null,
"chord": null,
"angle": null,
"numb": 20,
"bspace": "semi-cosine",
"airfoil": "NACA 2412"
},
{
"xpos": null,
"ypos": 1.8,
"zpos": null,
"chord": null,
"angle": null,
"numb": 15,
"bspace": "cosine",
"airfoil": "NACA 2412",
"controls": {
"aileron": {
"xhinge": 0.8,
"posgain": 1.0,
"neggain": 0.8,
"reverse": true,
"hvec": {"x": 0.0, "y": 0.0, "z": 0.0}
}
}
},
{
"xpos": 0.3,
"ypos": 2.25,
"zpos": 0.0,
"chord": 0.2,
"angle": -1.5
}
]
},
{
"name": "Horizontal Tail",
"mirror": true,
"numc": 8,
"cspace": "cosine",
"xpos": 2.3,
"ypos": 0.0,
"zpos": 0.1,
"angle": -1.8,
"sections": [
{
"xpos": 0.0,
"ypos": 0.0,
"zpos": 0.0,
"chord": 0.22,
"numb": 25,
"bspace": "cosine",
"controls": {
"elevator": {
"xhinge": 0.7,
"posgain": 1.0,
"neggain": 1.0,
"reverse": false,
"hvec": {"x": 0.0, "y": 0.0, "z": 0.0}
}
}
},
{
"xpos": 0.1,
"ypos": 0.7,
"zpos": 0.0,
"chord": 0.18
}
]
},
{
"name": "Vertical Tail",
"angle": 0.0,
"numc": 5,
"cspace": "cosine",
"xpos": 2.3,
"ypos": 0.0,
"zpos": 0.1,
"sections": [
{
"xpos": 0.0,
"ypos": 0.0,
"zpos": 0.0,
"chord": 0.25,
"angle": 0.0,
"numb": 15,
"bspace": "cosine"
},
{
"xpos": 0.1,
"ypos": 0.0,
"zpos": 0.4,
"chord": 0.15,
"angle": 0.0
}
]
}
],
"cases": [
{
"name": "Positive 1g Cruise",
"trim": "Looping Trim",
"density": 0.945,
"speed": 25.0,
"mass": 20.0,
"load factor": 1.0
},
{
"name": "Positive 5g Dive",
"trim": "Looping Trim",
"density": 0.945,
"speed": 50.0,
"mass": 20.0,
"load factor": 5.0
},
{
"name": "Negative 3g Dive",
"trim": "Looping Trim",
"density": 0.945,
"speed": 50.0,
"mass": 20.0,
"load factor": -3.0
},
{
"name": "60deg Banked Turn Cruise",
"trim": "Turning Trim",
"density": 0.945,
"speed": 25.0,
"mass": 20.0,
"bank angle": 60.0
},
{
"name": "Positive 1g Cruise + 15deg Side Slip",
"inherit": "Positive 1g Cruise",
"beta": 15.0
},
{
"name": "Positive 1g Cruise + 15deg Elevator",
"inherit": "Positive 1g Cruise",
"elevator": 15.0
},
{
"name": "Positive 1g Cruise - 15deg Elevator",
"inherit": "Positive 1g Cruise",
"elevator": -15.0
}
]
}Typical Python Script File "aircraft.py":
#%%
# Import Dependencies
from IPython.display import display_markdown
from pyvlm import latticesystem_from_json
from pyvlm.outputs.msh import latticeresult_to_msh
from pyvlm.outputs.prf import latticeresult_to_prf
#%%
# Import Geometry
jsonfilepath = '../files/Aircraft.json'
lsys = latticesystem_from_json(jsonfilepath)
#%%
# Display System
display_markdown(lsys)
#%%
# Display Results
for case in lsys.results:
lres = lsys.results[case]
display_markdown(lres)
#%%
# Mesh File Output
lres = lsys.results['Positive 1g Cruise + 15deg Side Slip']
latticeresult_to_msh(lres, '../results/Aircraft.msh')
#%%
# Pessure File Output
latticeresult_to_prf(lsys, '../results/Aircraft_pressures.json')
#%%
# 5g Trim Case
ltrm = lsys.results['Positive 5g Dive']
#%%
# Plot Lift Distribution
axl = ltrm.plot_trefftz_lift_force_distribution()
#%%
# Plot Y Force Distribution
axy = ltrm.plot_trefftz_side_force_distribution()
#%%
# Print Strip Forces
display_markdown(ltrm.strip_forces)
#%%
# Print Strip Coefficients
display_markdown(ltrm.strip_coefficients)
#%%
# Print Panel Forces
display_markdown(ltrm.panel_forces)
#%%
# Print Total Loads
display_markdown(ltrm.surface_loads)Mesh File Output:
You can generate a Gmsh mesh file (*.msh) directly from a Python script using the following code snippet.
lres = lsys.results['Positive 1g Cruise + 15deg Side Slip']
latticeresult_to_msh(lres, '../results/Aircraft.msh')This will output a mesh file to the specified location, which can then be viewed in Gmsh. The latest version of Gmsh can be downloaded at:
Use File > Open in Gmsh to open the mesh file with the pressure results.
A sample of the aircraft shown in Gmsh is captured below. Consult Gmsh help to operate Gmsh.
