SFGRAD

SFGRAD, Lab, SLKCN, Sldir, SLZER, SLOPE
Specifies a gradient (slope) for surface loads.

SOLUTION: FE 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.

Discipline	Surface Load Label	Label Description
Structural	PRES	pressure (real pressure only)
Thermal	CONV[1]	convection (bulk temperatures only)
	HFLUX[1]	heat flux
Electric	CHRGS	surface charge density
Diffusion	DFLUX	Diffusion flux

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.

In a mode-superposition harmonic or transient analysis, you must apply the load in the modal portion of the analysis. Mechanical APDL calculates a load vector and writes it to the MODE file, which you can apply via the LVSCALE command.

This command is also valid in PREP7.

Menu Paths

Main Menu>Preprocessor>Loads>Define Loads>Settings>For Surface Ld>Gradient

Main Menu>Solution>Define Loads>Settings>For Surface Ld>Gradient