Constraint: PTdSF

Description

These markers may belong to different bodies. As the markers move in space, the surface is calculated at every time step using CUBIC spline interpolation through the marker origins. Hence, the surface deforms as the markers move about.

Format

<Constraint_PTdSF
     id                   = "integer"
   [ label                = "string" ]     
     i_marker_id          = "integer"
     ref_dsurface_id      = "integer"
 />

Attributes

id

Element identification number, (integer>0). This number is unique among all Constraint_PTdSF elements.

label

The name of the Constraint_PTdSF element.

i_marker_id

Specifies a Reference_Marker whose origin defines the point that is constrained to move along the deformable curve.

ref_dsurface_id

Specifies the deformable surface used to define the Constraint_PTdSF element.

Example

<Reference_DeformSurface
     id                  = "1"
     end_type            = "NATURAL"
     num_marker_row      = "7"
     num_marker_col      = "7">
 30101490 30101500 30101510 30101520 30101530 30101540 30101540
 30101420 30109781 30113791 30117801 30121811 30125821 30101480
 30101350 30108711 30112721 30116731 30120741 30124751 30101410
 30101120 30102061 30103071 30104081 30105091 30106101 30101130
 30101140 30110571 30114581 30118591 30122601 30126611 30101200
 30101210 30111641 30115651 30119661 30123671 30127681 30101270
 30101280 30101290 30101300 30101310 30101320 30101330 30101340
  </Reference_DeformSurface>
 
 <Constraint_PTdSF
     id                  = "1"
     i_marker_id         = "30107780"
     ref_dsurface_id     = "1"
  />     
 
 <Post_Graphic
     id                  = "500000"
     type                = "DeformSurface"
     surface_id          = "1"
     nseg_u              = "30"
     nseg_v              = "30" 
  />

Comments

1. The Reference_DeformSurface element does not possess any inherent inertia, stiffness or damping properties. Additional modeling elements are necessary to capture these effects. See the Example.
2. The markers used to define the Reference_DeformSurface may belong to different bodies which may be of type Body_Point, Body_Rigid, or Body_Flexible.
3. The Constraint_PTdSF element can be thought of as a generalization of the Constraint_PTSF element. In fact, when all the markers belong to a single rigid body, Constraint_PTdSF reduces to Constraint_PTSF.
4. To correctly model a Constraint_PTdSF element, you must ensure that the point which is referenced by the i_marker_id will always fall in range of the deformable surface throughout the simulation. MotionSolve calculates a (u, v) value for the point's current position with respect to the deformable surface. This (u, v) value must always stay within range of the defined u_span and v_span, for example.

   -u_span/2 ≤ u ≤ + u_span/2

   -v_span/2 ≤ v ≤ + v_span/2

   If the current u or v value goes out of this range, MotionSolve will hold the u or v value at the boundary until the point falls back in range of the deformable surface. However, this may lead to incorrect results. You are encouraged to check the results for correctness in such a situation. For more information, please refer to the Reference_DeformSurface model element.