Model VSM LLT

Enumeration of the implemented model types.

Elements

• VSM: Vortex Step Method
• LLT: Lifting Line Theory

WingType `RECTANGULAR` `CURVED` `ELLIPTICAL`

Enumeration of the implemented wing types.

Elements:

• RECTANGULAR
• CURVED
• ELLIPTICAL

AeroModel LEI_AIRFOIL_BREUKELS POLAR_VECTORS POLAR_MATRICES INVISCID

Enumeration of the implemented aerodynamic models. See also: AeroData

Elements

• LEI_AIRFOIL_BREUKELS: Polynom approximation for leading edge inflatable kites
• POLAR_VECTORS: Polar vectors as function of alpha (lookup tables with interpolation)
• POLAR_MATRICES: Polar matrices as function of alpha and delta (lookup tables with interpolation)
• INVISCID

where alpha is the angle of attack, delta is trailing edge angle.

PanelDistribution LINEAR COSINE COSINE_VAN_GARREL SPLIT_PROVIDED UNCHANGED

Enumeration of the implemented panel distributions.

Elements

• LINEAR # Linear distribution
• COSINE # Cosine distribution
• COSINE_VAN_GARREL # van Garrel cosine distribution
• SPLIT_PROVIDED # Split provided sections
• UNCHANGED # Keep original sections

InitialGammaDistribution ELLIPTIC ZEROS

Enumeration of the implemented initial gamma distributions.

Elements

• ELLIPTIC
• ZEROS

SolverStatus FEASIBLE INFEASIBLE FAILURE

Enumeration to report back the validity of the result of the solve! function. Used in the VSMSolution struct.

Elements

• FEASIBLE: The gamma distribution is physically feasible
• INFEASIBLE: The gamma distribution is physically infeasible
• FAILURE: The result did not converge within the maximal number of iterations

const MVec3 = MVector{3, Float64}

Basic 3-dimensional vector, stack allocated, mutable.

const PosVector=Union{MVec3, Vector}

Position vector, either a MVec3 or a Vector for use in function signatures.

const VelVector=Union{MVec3, Vector}

Velocity vector, either a MVec3 or a Vector for use in function signatures.

AeroData= Union{
    Nothing,
    NTuple{2, Float64},
    Tuple{Vector{Float64}, Vector{Float64}, Vector{Float64}, Vector{Float64}},
    Tuple{Vector{Float64}, Vector{Float64}, Matrix{Float64}, Matrix{Float64}, Matrix{Float64}}
}

Union of different definitions of the aerodynamic properties of a wing section. See also: AeroModel

• nothing for INVISCID
• (tube_diameter, camber) for LEI_AIRFOIL_BREUKELS
• (alpha_range, cl_vector, cd_vector, cm_vector) for POLAR_VECTORS
• (alpha_range, delta_range, cl_matrix, cd_matrix, cm_matrix) for POLAR_MATRICES

where alpha is the angle of attack [rad], delta is trailing edge angle [rad], cl the lift coefficient, cd the drag coefficient and cm the pitching moment coefficient. The camber of a kite refers to the curvature of its airfoil shape. The camber is typically measured as the maximum distance between the mean camber line (the line equidistant from the upper and lower surfaces) and the chord line of the airfoil.

@with_kw mutable struct Section

Represents a wing section with leading edge, trailing edge, and aerodynamic properties.

Fields

• LE_point::MVec3 = zeros(MVec3): Leading edge point coordinates
• TE_point::MVec3 = zeros(MVec3): Trailing edge point coordinates
• aero_model::AeroModel = INVISCID: AeroModel
• aero_data::AeroData = nothing: See: AeroData

Section(LE_point::PosVector, TE_point::PosVector, aero_model)

Create a new wing section with the specified leading edge point, trailing edge point, and aerodynamic model.

Arguments

• LE_point::PosVector: Leading edge point coordinates
• TE_point::PosVector: Trailing edge point coordinates
• aero_model::AeroModel: Aerodynamic model type (e.g., INVISCID, POLAR_VECTORS)

Returns

• Section: A new section with the specified parameters and no aerodynamic data

Wing

Represents a wing composed of multiple sections with aerodynamic properties.

Fields

• n_panels::Int16: Number of panels in aerodynamic mesh
• n_groups::Int16: Number of panel groups
• spanwise_distribution::PanelDistribution: PanelDistribution
• spanwise_direction::MVec3: Wing span direction vector
• sections::Vector{Section}: Vector of wing sections, see: Section
• refined_sections::Vector{Section}: Vector of refined wing sections, see: Section
• remove_nan::Bool: Wether to remove the NaNs from interpolations or not

Wing(n_panels::Int;
     n_groups=n_panels,
     spanwise_distribution::PanelDistribution=LINEAR,
     spanwise_direction::PosVector=MVec3([0.0, 1.0, 0.0]),
     remove_nan::Bool=true)

Constructor for a Wing struct with default values that initializes the sections and refined sections as empty arrays.

Parameters

• n_panels::Int: Number of panels in aerodynamic mesh
• n_groups::Int: Number of panel groups in aerodynamic mesh
• spanwise_distribution::PanelDistribution = LINEAR: PanelDistribution
• spanwise_direction::MVec3 = MVec3([0.0, 1.0, 0.0]): Wing span direction vector
• remove_nan::Bool: Wether to remove the NaNs from interpolations or not

RamAirWing <: AbstractWing

A ram-air wing model that represents a curved parafoil with deformable aerodynamic surfaces.

Core Features

• Curved wing geometry derived from 3D mesh (.obj file)
• Aerodynamic properties based on 2D airfoil data (.dat file)
• Support for control inputs (twist angles and trailing edge deflections)
• Inertial and geometric properties calculation

Notable Fields

• n_panels::Int16: Number of panels in aerodynamic mesh
• n_groups::Int16: Number of control groups for distributed deformation
• mass::Float64: Total wing mass in kg
• gamma_tip::Float64: Angular extent from center to wing tip
• inertia_tensor::Matrix{Float64}: Full 3x3 inertia tensor in the kite body frame
• T_cad_body::MVec3: Translation vector from CAD frame to body frame
• R_cad_body::MMat3: Rotation matrix from CAD frame to body frame
• radius::Float64: Wing curvature radius
• theta_dist::Vector{Float64}: Panel twist angle distribution
• delta_dist::Vector{Float64}: Trailing edge deflection distribution

See constructor RamAirWing(obj_path, dat_path; kwargs...) for usage details.

RamAirWing(obj_path, dat_path; kwargs...)

Create a ram-air wing model from 3D geometry and airfoil data files.

This constructor builds a complete aerodynamic model by:

1. Loading or generating wing geometry from the .obj file
2. Creating aerodynamic polars from the airfoil .dat file
3. Computing inertial properties and coordinate transformations
4. Setting up control surfaces and panel distribution

Arguments

• obj_path: Path to .obj file containing 3D wing geometry
• dat_path: Path to .dat file containing 2D airfoil profile

Keyword Arguments

• crease_frac=0.9: Normalized trailing edge hinge location (0-1)
• wind_vel=10.0: Reference wind velocity for XFoil analysis (m/s)
• mass=1.0: Wing mass (kg)
• n_panels=56: Number of aerodynamic panels across wingspan
• n_groups=4: Number of control groups for deformation
• n_sections=n_panels+1: Number of spanwise cross-sections
• align_to_principal=false: Align body frame to principal axes of inertia
• spanwise_distribution=UNCHANGED: Panel distribution type
• remove_nan=true: Interpolate NaN values in aerodynamic data
• alpha_range=deg2rad.(-5:1:20): Angle of attack range for polars (rad)
• delta_range=deg2rad.(-5:1:20): Trailing edge deflection range for polars (rad)
• prn=true: if info messages shall be printed

Returns

A fully initialized RamAirWing instance ready for aerodynamic simulation.

Example

# Create a ram-air wing from geometry files
wing = RamAirWing(
    "path/to/wing.obj",
    "path/to/airfoil.dat";
    mass=1.5,
    n_panels=40,
    n_groups=4
)

@with_kw mutable struct BodyAerodynamics{P}

Main structure for calculating aerodynamic properties of bodies. Use the constructor to initialize.

Fields

• panels::Vector{Panel}: Vector of Panel structs
• wings::Union{Vector{Wing}, Vector{RamAirWing}}: A vector of wings; a body can have multiple wings
• va::MVec3 = zeros(MVec3): A vector of the apparent wind speed, see: MVec3
• omega::MVec3 = zeros(MVec3): A vector of the turn rates around the kite body axes
• gamma_distribution=zeros(Float64, P): A vector of the circulation of the velocity field; Length: Number of segments. [m²/s]
• alpha_uncorrected=zeros(Float64, P): angles of attack per panel
• alpha_corrected=zeros(Float64, P): corrected angles of attack per panel
• stall_angle_list=zeros(Float64, P): stall angle per panel
• alpha_array::MVector{P, Float64} = zeros(Float64, P)
• v_a_array::MVector{P, Float64} = zeros(Float64, P)
• work_vectors::NTuple{10, MVec3} = ntuple(_ -> zeros(MVec3), 10)
• AIC::Array{Float64, 3} = zeros(3, P, P)
• projected_area::Float64 = 1.0: The area projected onto the xy-plane of the kite body reference frame [m²]
• y::MVector{P, Float64} = zeros(MVector{P, Float64})
• cache::Vector{PreallocationTools.LazyBufferCache{typeof(identity), typeof(identity)}} = [LazyBufferCache() for _ in 1:5]

Solver

Main solver structure for the Vortex Step Method.See also: solve

Attributes

General settings

• aerodynamic_model_type::Model = VSM: The model type, see: Model
• density::Float64 = 1.225: Air density [kg/m³]
• max_iterations::Int64 = 1500
• rtol::Float64 = 1e-5: relative error
• tol_reference_error::Float64 = 0.001
• relaxation_factor::Float64 = 0.03: Relaxation factor for convergence

Damping settings

• is_with_artificial_damping::Bool = false: Whether to apply artificial damping
• artificial_damping::NamedTuple{(:k2, :k4), Tuple{Float64, Float64}} = (k2=0.1, k4=0.0): Artificial damping parameters

Additional settings

• type_initial_gamma_distribution::InitialGammaDistribution = ELLIPTIC: see: InitialGammaDistribution
• core_radius_fraction::Float64 = 1e-20:
• mu::Float64 = 1.81e-5: Dynamic viscosity [N·s/m²]
• is_only_f_and_gamma_output::Bool = false: Whether to only output f and gamma

Solution

sol::VSMSolution = VSMSolution(): The result of calling solve!

VSMSolution

Struct for storing the solution of the solve! function. Must contain all info needed by KiteModels.jl.

Attributes

• panel_width_array::Vector{Float64}: Width of the panels [m]
• alpha_array::Vector{Float64}: Angle of attack of each panel relative to the apparent wind [rad]
• cl_array::Vector{Float64}: Lift coefficients of the panels [-]
• cd_array::Vector{Float64}: Drag coefficients of the panels [-]
• cm_array::Vector{Float64}: Pitching moment coefficients of the panels [-]
• panel_lift::Vector{Float64}: Lift force of the panels [N]
• panel_drag::Vector{Float64}: Drag force of the panels [N]
• panel_moment::Vector{Float64}: Pitching moment around the spanwise vector of the panels [Nm]
• f_body_3D::Matrix{Float64}: Matrix of the aerodynamic forces (x, y, z vectors) [N]
• m_body_3D::Matrix{Float64}: Matrix of the aerodynamic moments [Nm]
• gamma_distribution::Union{Nothing, Vector{Float64}}: Vector containing the panel circulations.
• force::MVec3: Aerodynamic force vector in KB reference frame [N]
• moment::MVec3: Aerodynamic moments [Mx, My, Mz] around the reference point [Nm]
• force_coeffs::MVec3: Aerodynamic force coefficients [CFx, CFy, CFz] [-]
• moment_coeffs::MVec3: Aerodynamic moment coefficients [CMx, CMy, CMz] [-]
• moment_dist::Vector{Float64}: Pitching moments around the spanwise vector of each panel. [Nm]
• moment_coeff_dist::Vector{Float64}: Pitching moment coefficient around the spanwise vector of each panel. [-]
• solver_status::SolverStatus: enum, see SolverStatus