OpenAeroStruct VLM

The OasDiscipline wraps a complete OpenAeroStruct (OAS) vortex-lattice method (VLM) aerodynamic analysis as a single Philote discipline. Unlike the NACA and XFOIL disciplines which subclass ExplicitDiscipline, this discipline uses the OpenMdaoSubProblem pattern to package an entire OpenMDAO Group as a gRPC-servable discipline.

Architecture

The discipline contains two internal components:

┌─────────────────────────────────────────────────────┐
│  OasDiscipline (Philote gRPC server)                │
│                                                     │
│  ┌──────────────┐       ┌────────────────────────┐  │
│  │   Geometry    │──mesh──▶    AeroPoint (VLM)    │  │
│  │  (wing shape) │       │  (vortex-lattice solve)│  │
│  └──────────────┘       └────────────────────────┘  │
│                                                     │
│  Inputs:                    Outputs:                │
│    v          (m/s)           CL  (scalar)          │
│    alpha      (deg)           CD  (scalar)          │
│    Mach_number                CM  (3-vector)        │
│    re         (1/m)                                 │
│    rho        (kg/m^3)                              │
│    cg         (3-vector, m)                         │
└─────────────────────────────────────────────────────┘

Geometry applies design variables (twist, chord, shear) to a baseline mesh.

AeroPoint runs the VLM aerodynamic analysis on the deformed mesh at the specified flight condition and computes lift, drag, and moment coefficients.

The OpenMdaoSubProblem Pattern

Where the NACA/XFOIL examples wrap external executables using ExplicitDiscipline, this example takes advantage of the fact that OAS is already an OpenMDAO Group. The OpenMdaoSubProblem base class handles the wrapping:

1. Create an om.Group (OasAeroGroup) containing the solver components and their internal connections.
2. Subclass OpenMdaoSubProblem and call self.add_group(group) to embed the Group in an internal om.Problem.
3. Map inputs/outputs using self.add_mapped_input() and self.add_mapped_output() to define the Philote-level interface.

At runtime, compute() copies inputs into the internal problem, calls run_model(), and copies outputs back -- all handled by the base class.

When to use which pattern

Use case	Recommended class
Wrapping an external executable (file I/O)	ExplicitDiscipline
Wrapping an OpenMDAO Group or Component	OpenMdaoSubProblem
Need fine-grained control over compute logic	ExplicitDiscipline
Solver already built as an OpenMDAO model	OpenMdaoSubProblem

Inputs and Outputs

Inputs

Philote Name	OpenMDAO Path	Shape	Units	Description
v	v	(1,)	m/s	Freestream velocity
alpha	alpha	(1,)	deg	Angle of attack
Mach_number	Mach_number	(1,)	--	Mach number
re	re	(1,)	1/m	Reynolds number per unit length
rho	rho	(1,)	kg/m^3	Air density
cg	cg	(3,)	m	Center of gravity position

Outputs

Philote Name	OpenMDAO Path	Shape	Units	Description
CL	aero_point_0.wing_perf.CL	(1,)	--	Lift coefficient
CD	aero_point_0.wing_perf.CD	(1,)	--	Drag coefficient
CM	aero_point_0.CM	(3,)	--	Moment coefficient vector

Mesh Configuration

Pass a mesh_dict to OasDiscipline to change the wing planform:

from philote_examples import OasDiscipline

# Default: rectangular wing (10 m span, 1 m chord, 7 spanwise panels)
discipline = OasDiscipline()

# CRM wing with 13 spanwise panels
discipline = OasDiscipline(
    mesh_dict={
        "num_y": 13,
        "num_x": 3,
        "wing_type": "CRM",
        "symmetry": True,
        "num_twist_cp": 5,
    }
)

The default mesh configuration is:

{
    "num_y": 7,
    "num_x": 2,
    "wing_type": "rect",
    "symmetry": True,
    "span": 10.0,
    "root_chord": 1.0,
}

Surface Properties

Use surface_options to override defaults like viscous drag or baseline CD:

discipline = OasDiscipline(
    surface_options={
        "with_viscous": True,
        "CD0": 0.015,
        "with_wave": True,
    }
)

The default surface properties include:

Property	Default	Description
CL0	0.0	Baseline lift coefficient
CD0	0.0	Baseline drag coefficient
k_lam	0.05	Fraction of chord with laminar flow
t_over_c_cp	[0.15]	Thickness-to-chord ratio
c_max_t	0.303	Chordwise location of max thickness
with_viscous	False	Enable viscous drag estimation
with_wave	False	Enable wave drag estimation

Example Usage

from philote_examples import OasDiscipline
from philote_mdo.general import run_server

# Create the discipline with default rectangular wing
discipline = OasDiscipline()

# Start the gRPC server on port 50051
run_server(discipline, port=50051)