SPLINE2

Bulk Data Entry Defines a beam spline for interpolating motion and/or forces for aeroelastic problems on aerodynamic geometries defined by regular arrays of aerodynamic points.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
SPLINE2 EID CAERO ID1 ID2 SETG DZ DTOR CID
DTHX DTHY USAGE

Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
SPLINE2 57 32 12 13 11 0.0 1.0 4
1.0

Definitions

Field Contents SI Unit Example
EID Unique spline identification number.

(Integer > 0)
CAERO Aero-element (CAEROi entry ID) that is to be interpolated.

(Integer > 0)
ID1, ID2 ID1 and ID2 are the IDs of the first and last panel or slender body mesh elements, respectively, in the CAEROi definition.

(Integer > 0; ID2 > ID1)
SETG Refers to the SETi entry that lists the structural grid points to which the spline is attached.

(Integer > 0)
DZ Linear attachment flexibility.

Default = 0.0 (Real ≥ 0.0)
DTOR Torsional flexibility ratio (EI/GJ).

Default = 1.0 (Real > 0.0, use 1.0 for bodies)
CID Rectangular coordinate system for which the y-axis defines the axis of the spline. The y-axis of this coordinate system cannot be perpendicular to the element and must have a non-zero projection on the element. This field is not used for slender bodies (CAERO2).

(Integer ≥ 0)
DTHX, DTHY Rotational attachment flexibility.
DTHX
For rotation about the spline’s X-axis (in-plane bending rotations).
DTHY
For rotation about the spline’s Y-axis (torsion).
For slender bodies, DTHX is not used and DTHY is used for the slope.

(Real ≥ 0)
USAGE Spline usage flag. 8
BOTH (Default)
For both force and displacement transformations.

Comments

  1. The interpolated points (k-set) will be defined by aero elements.
  2. For CAERO1 lifting bodies, the spline axis for panels is the projection of the y-axis of coordinate system CID, projected onto the plane of the panel. For CAERO2 slender bodies, the spline axis is parallel to the x-axis of the aerodynamic coordinate system.
  3. The flexibilities DZ, DTHX, and DTHY are used for smoothing. Zero attachment flexibility values imply rigid attachment (as in, no smoothing).
  4. The continuation line is required.
  5. The SPLINE2 EID must be unique with respect to all SPLINEi entries.
  6. DTOR is the ratio of rotational to linear deflection and, in lieu of a more accurate estimate, a value of 1.0 is recommended. A different value may be used; for example, if DTOR is much greater than 1.0, primarily rotational deflection will occur; if DTOR is much less than 1.0, primarily linear deflection will occur.
  7. If a SPLINE2 element only references one grid point, the job will fail without a message.
  8. The USAGE field allows you to specify that the particular spline interpolant defined in this entry is used for both the force transformation and the displacement transformation. Currently only the BOTH option is supported for the USAGE field.