PLOADSF

Bulk Data Entry Parameters of pressure loads on a surface defined by a SURF Bulk Data Entry or SET Bulk Data Entry.

The SURF format of type ELFACE and the SURF/SET format of type ELEM are supported.

Format A

Pressure normal to local element surfaces (Type = NORMAL)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PLOADSF SID ELSET/SURF Type P

Format B

Hydrostatic pressure (Type = HYDRO)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PLOADSF SID ELSET/SURF Type P1 CID Z0 Z1

Format C

Directional surface traction (Type = DIREC) and Shear surface traction (Type = SHEAR)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PLOADSF SID ELSET/SURF Type P CID N1 N2 N3

Definitions

Field Contents SI Unit Example
SID Load set identification number.

No default (Integer > 0)
ELSET/SURF Surface identification. The following surface definition options are supported:
  • SURF Bulk Data Entry with flag ELFACE
  • SURF Bulk Data Entry using the alternative SET format, of TYPE = ELEM
  • SET Bulk Data Entry of TYPE = ELEM
Integer
Specifies an identification number for this entity.
<String>
Specifies a user-defined string label for this entity. 6
blank (Default)

No default (Integer > 0 or <String>)
Type Pressure type applied.
NORMAL (Default)
Pressure normal to local element surfaces.
DIREC
Directional surface traction.
HYDRO
Hydrostatic pressure.
SHEAR
Shear surface traction.

(Character)
P Constant pressure magnitude.

No default (Real)
P1 Hydrostatic pressure magnitude at Z1. 4

No default (Real)
CID Coordinate system identification number.
0 or blank
Identifies the basic coordinate system. Spherical coordinate systems are invalid for type HYDRO.

Default = 0 (Integer > 0, or blank)
ZO Z-coordinates of the zero-pressure level, in the user-defined coordinate system. 3

No default (Real)
Z1 Z-coordinates of the level at which the hydrostatic pressure P1 is defined, in the user-defined coordinate system. 3 4

No default (Real)
N1, N2, N3 Components of a vector measured in the user-defined coordinate system. The vector is normalised internally such that it does not contribute to the magnitude of the load.

For Type DIREC, the vector defines the direction of the load.

For Type SHEAR, the projection of the vector on local element surfaces gives the direction of the shear traction. If the vector is perpendicular to the face of an element, the corresponding shear pressure will be set to 0.

Default = 0 (Real)

Comments

  1. The magnitude of surface tractions of types NORMAL, DIREC and SHEAR is assumed be constant.
  2. The direction for surface tractions of types NORMAL and HYDRO is consistent with the normal direction of the referenced surface.
  3. If Type = HYDRO, if the basic coordinate system is used in axisymmetric analysis defined in xz- and xy- planes, Z0 and Z1 specify values of the z- and y-coordinate, respectively.
  4. If Type = HYDRO, the magnitude of the hydrostatic pressure, varies linearly between Z0 and Z1 and vanishes above Z0 (Figure 1). As Z0 is the zero-pressure level and Z1 is the level at which P1 is defined, Z0 must be greater than Z1 (Z0 > Z1), else OptiStruct will error out.
    Figure 1. Definition of the Hydrostatic Pressure


  5. Only the complete follower option, for example, FLLWER = 1, is provided for the hydrostatic pressure of type HYDRO, and other options (FLLWER = 2 and 3) will be converted internally, if specified. For types NORMAL, DIREC and SHEAR, all the follower options are supported.
  6. String based labels allow for easier visual identification, including when being referenced by other entries. For more details, refer to String Label Based Input File.