Mesh and Surface Dictionaries

Mesh Dict

Here is a list of the keys and default values of the mesh_dict, which is used to generate a mesh, e.g. mesh = generate_mesh(mesh_dict).

Mesh definition

Key	Default value	Units	Description
num_x	3		Number of chordwise vertices. Needs to be 2 or an odd number.
num_y	5		Number of spanwise vertices for the entire wing. When symmetry = True, the number of vertices for a half wing will be (num_y + 1) / 2.
span	10.0	m	Full wingspan, even for symmetric cases.
root_chord	1.0	m	Root chord length.
span_cos_spacing	0		Spanwise cosine spacing. 0 for uniform spanwise panels, 1 for cosine-spaced panels.
chord_cos_spacing	0		Chordwise cosine spacing.
wing_type	“rect”		Initial shape of the wing. "rect" or "CRM".
symmetry	True		If true, OAS models half of the wing reflected across the plane y = 0.
offset	np.array([0, 0, 0])	m	Coordinates to offset the surface from its default location.
num_twist_cp	2		Number of twist control points. Only relevant when wing_type = "CRM".

Surface Dict

Here is a non-exclusive list of the surface dict keys. The surface dict will be provided to Groups, including Geometry, AeroPoint, and AerostructGeometry.

Surface definition

Key	Example value	Units	Description
name	“wing”		Name of the surface.
symmetry	True or False		If true, OAS models half of the wing reflected across the plane y = 0.
S_ref_type	“wetted” or “projected”		How we compute the wing reference area.
mesh	3D ndarray	m	x, y, z coordinates of the mesh vertices, can be created by generate_mesh.
span	10.0	m	Wing span.
taper	0.5		Wing taper ratio.
sweep	10.0	deg	Wing sweep angle.
dihedral	5.0	deg	Wing dihedral.
twist_cp	np.array([0, 5])	deg	B-spline control points for twist distribution. Array convention is [wing tip, ..., root] in symmetry cases, and [tip, ..., root, ... tip] when symmetry = False.
chord_cp	np.array([0.1, 5])		B-spline control points for chord distribution. This is a chord scaler applied to the initial mesh, not the chord value [m] itself. Array convention is the same as twist_cp.
xshear_cp	np.array([0.1, 0.2])	m	B-spline control points for the x-wise shear deformation of the wing.
yshear_cp	np.array([0.1, 0.2])	m	B-spline control points for the y-wise shear deformation of the wing.
zshear_cp	np.array([0.1, 0.2])	m	B-spline control points for the z-wise shear deformation of the wing.
ref_axis_pos	0.25		Position of reference axis along the chord about which to apply twist, chord, taper, and span geometry transformations. 1 is the trailing edge, 0 is the leading edge.

Aerodynamics definitions

Key	Example value	Units	Description
CL0	0.0		Lift coefficient of the surface at 0 angle of attack.
CD0	0.015		Drag coefficient of the surface at 0 angle of attack.
with_viscous	True or False		If true, compute viscous drag
with_wave	True or False		If true, compute wage drag
groundplane	True or False		If true, compute ground effect.
k_lam	0.05		Airfoil property for viscous drag calculation. Percentage of chord with lanimar flow.
t_over_c_cp	np.array([0.12, 0.12])		B-spline control points for airfoil thickness-over-chord ratio
c_max_t	0.303		Chordwise nondimensional location of the maximum airfoil thickness.

Structure definitions

Key	Example value	Units	Description
fem_model_type	“tube” or “wingbox”		Structure model.
E	73.1e9	Pa	Young’s modulus
G	27.5e9	Pa	Shear modulus
yield	420.0e6 / 1.5	Pa	Allowable yield stress including the safety factor.
mrho	2.78e3	kg/m^3	Material density
fem_origin	0.35		Normalized chordwise location of the spar
wing_weight_ratio	2.0		Ratio of the total wing weight (including non-structural components) to the wing structural weight.
exact_failure_constraint	True or False		If False, we use KS function to aggregate the stress constraint.
struct_weight_relief	True or False		Set True to add the weight of the structure to the loads on the structure.
distributed_fuel_weight	True or False		Set True to distribute the fuel weight across the entire wing.
fuel_density	803.0	kg/m^3	Fuel density only needed if the fuel-in-wing volume constraint is used)
Wf_reserve	15000.0	kg	Reserve fuel mass
n_point_masses	1		Number of point masses in the system (for example, engine)

Structure parameterization for tubular spar

Key	Example value	Units	Description
thickness_cp	np.array([0.01, 0.02])	m	B-spline control point of the tube thickness distribution.
radius_cp	np.array([0.1, 0.2])	m	B-spline control point of the tube radius distribution.

Structure parameterization for wingbox

Key	Example value	Units	Description
spar_thickness_cp	np.array([0.004, 0.01])	m	Control point of spar thickness distribution.
skin_thickness_cp	np.array([0.005, 0.02])	m	Control point of skin thickness distribution.
original_wingbox _airfoil_t_over_c	0.12		Thickness-over-chord ratio of airfoil provided for the wingbox cross-section.
strength_factor _for_upper_skin	1.0		A factor to adjust the yield strength of the upper skin relative to the lower skin.
data_x_upper	1D ndarray		x coordinates of the wingbox cross-section’s upper surface for an airfoil with the chord scaled to 1.
data_y_upper	1D ndarray		y coordinates of the wingbox cross-section’s upper surface
data_x_lower	1D ndarray		x coordinates of the wingbox cross-section’s lower surface
data_y_lower	1D ndarray		y coordinates of the wingbox cross-section’s lower surface

FFD parameters

Key	Example value	Units	Description
mx	2		Number of the FFD control points in the x direction.
my	2		Number of the FFD control points in the y direction.