VAP 3.5

The MATLAB version of the higher-order potential flow code FreeWake.

This markdown file holds information and records of VAP 3, development of a new input format for future versions of VAP. Similar to previous input files, parameters of the flight vehicle geometry are stored in ASCII text file but in XML 1.0 language. This will provide freedom for future versions of VAP and enable analysis of complex vehicle geometry and configuration.

VAP 3.5 File Format Specifications

Legend

• (*) Multiple Entry
• [FW] Parameter exists in FreeWake
• [VAP2] Parameter introduced to VAP2
• [VAP3] Parameter introduced to VAP3

Input Structure

Setting

• Setting
  • relax (True | False) Toggle wake relaxation or fixed wake
  • steady (True | False)
  • maxtime Maximum number of time steps
  • delta_time Inteval of each time step (second)
  • start_force Timestep number to begin force calculations
  • stiff_wing (1 | 0) Toggle on (1) or off (0) structure model
  • fixed_lift (true | false) Toggle fixed lift where lift = weight and freestream is calcualted
  • gust_mode Select gust mode, 0 - No gust, 1 - Sine wave gust, 2 - 1-cosine gust, 3 - Sharp edge gust

Condition

• condition
  • density Fluid density (kg/m^3)
  • kin_viscosity Kinematic viscosity (m^2/s)
  • gust_amplitude
  • gust_length
  • gust_start

Vehicle

• vehicle*
  • global_x X position of the entire vehicle (Position of vehicle's origin in global reference frame)
  • global_y Y position of the entire vehicle
  • global_z Z position of the entire vehicle
  • weight Weight of vehicle (N)
  • interference_drag Percent of interference drag (often due to fuselage)
  • speed Freestream velocity of the vehicle (m/s). Set to 'nan' when doing fixed-lift analysis
  • alpha Overall angle of attack of the entire vehicle (deg)
  • beta Overall angle of sideslip of the entire vehicle (deg)
  • roll Overall angle of roll of the entire vehicle (deg)
  • fpa FPA (Flight Path Angle) = Pitch - AOA (deg)
  • track Track heading of the entire vehicle (deg)
  • radius Turning radius of the vehicle (zero = straight) (m)
  • ref_area Reference area of the wing (m^2)
  • ref_span Reference span of the wing (m)
  • ref_cmac Mean aerodynamic chord of the wing (m)
  • wing*
    • symmetry (True | False)
    • incidence Angle of incidence of the root (deg)
    • trimable Defines a surface that can be trimmed (True | False)
    • triangular_elements Uses triangular elements, use with caution (True | False)
    • chordwise_elements Number of chordwise elements
    • vehicle_x X reference position of wing
    • vehicle_y Y reference position of wing
    • vehicle_z Z reference position of wing
    • panel*
      • spanwise_elements Number of spanwise elements in this panel
      • strip_airfoil Airfoil name for this panel
      • section*
        • wing_x X position of section leading edge with respect to vehicle_x (m)
        • wing_y Y position of section leading edge with respect to vehicle_y (m)
        • wing_z Z position of section leading edge with respect to vehicle_z (m)
        • chord Chord length of section (m)
        • twist Twist angle of section (deg)
  • rotor*
    • rpm Rotational speed of rotor (RPM)
    • collective Collective blade pitch (deg)
    • ref_diam Rotor diameter (m)
    • rotation_direction Rotational direction, CCW - Counterclockwise, CW - clockwise
    • veh_x_hub X location of center of rotor with respect to vehicle origin (m)
    • veh_y_hub Y location of center of rotor with respect to vehicle origin (m)
    • veh_z_hub Z location of center of rotor with respect to vehicle origin (m)
    • veh_x_axis Axis of rotation unit vector X-component with respect to vehicle origin (m)
    • veh_y_axis Axis of rotation unit vector Y-component with respect to vehicle origin (m)
    • veh_z_axis Axis of rotation unit vector Z-component with respect to vehicle origin (m)
    • blades Number of blades
    • chordwise_elements Number of chordwise elements
    • panel*
      • strip_airfoil Airfoil name for this panel
      • spanwise_elements Number of spanwise elements
      • section*
        • rotor_x X position of section leading edge with respect to hub and XY plane (m)
        • rotor_y Y position of section leading edge with respect to hub and XY plane (m)
        • rotor_z Z position of section leading edge with respect to hub and XY plane (m)
        • chord Chord length of section (m)
        • twist Twist angle of section (deg)

Notes

Default Unit

All numerical input would have a default unit assigned. (e.g. meters for the reference span). This can be setup with a unit tag under the numerical parameter such that specific units can be converted to the default unit in future VAP releases.

For example: <span unit='feet'>5</span>

would yield the same result as <span>1.524</span>

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