**SFGRAD****SFGRAD**, `Lab`

, `SLKCN`

, `Sldir`

, `SLZER`

, `SLOPE`

**Specifies a gradient (slope) for surface loads.**

`Lab`

Valid surface load label. Load labels are listed
under "Surface Loads" in the input table for each element type in
the *Element Reference*.

Thermal labels CONV and HFLUX are mutually
exclusive.

`SLKCN`

Reference number of slope coordinate system (used
with `Sldir`

and `SLZER `

to determine COORD). Defaults to 0 (the global Cartesian coordinate
system).

`Sldir`

Slope direction in coordinate system `SLKCN`

:

**X**
| — | Slope is along X direction (default).
Interpreted as R direction for non-Cartesian coordinate systems. |

**Y**
| — | Slope is along Y direction. Interpreted
as θ direction for non-Cartesian coordinate systems. |

**Z**
| — | Slope is along Z direction. Interpreted
as Φ direction for spherical or toroidal coordinate systems. |

`SLZER`

Coordinate location (degrees for angular input) where
slope contribution is zero (CVALUE = VALUE). Allows the slope contribution
to be shifted along the slope direction. For angular input, `SLZER`

should be between ±180° if the singularity
[**CSCIR**] is at 180° and should be between 0°
and 360° if the singularity is at 0°.

`SLOPE`

Slope value (load per unit length or per degree).

## Notes

Specifies a gradient (slope) for surface loads. All surface
loads issued with the **SF**, **SFE**, **SFL**, or **SFA** commands while
this specification is active will have this gradient applied (for
complex pressures, only the real component will be affected; for convections,
only the bulk temperature will be affected). The load value, CVALUE,
calculated at each node is:

CVALUE = VALUE + (`SLOPE`

X (COORD-`SLZER`

))

where VALUE is the load value specified on the subsequent **SF**, **SFE**, **SFL**, or **SFA** commands and COORD is the coordinate value (in the `Sldir`

direction of coordinate system `SLKCN`

) of the node. Only one **SFGRAD** specification
may be active at a time (repeated use of this command replaces the
previous specification with the new specification). Issue **SFGRAD** (with blank fields) to remove the specification.
Issue **SFGRAD**,STAT to show the current command
status. The **SFGRAD** specification (if active) is
removed when the **LSREAD** (if any) command is issued.

**SFGRAD** does not work for tabular boundary
conditions.

This command is also valid in PREP7.