ansys.mapdl.core.Mapdl.sfa#

Mapdl.sfa(area='', lkey='', lab='', value='', value2='', **kwargs)#

Specifies surface loads on the selected areas.

Mechanical APDL Command: SFA

Parameters:
areastr

Area to which surface load applies. If ALL, apply load to all selected areas ( asel ). If Area = P, graphical picking is enabled and all remaining command fields are ignored (valid only in the GUI). A component may be substituted for Area.

lkeystr

Load key associated with surface load (defaults to 1). Load keys (1,2,3, etc.) are listed under “Surface Loads” in the input data table for each element type in the Element Reference. LKEY is ignored if the area is the face of a volume region meshed with volume elements.

labstr

Valid surface load label. Load labels are listed under “Surface Loads” in the input table for each area type in the Element Reference.

This command contains some tables and extra information which can be inspected in the original

documentation pointed above… _sfa1:

Thermal labels CONV and HFLUX are mutually exclusive.

For an acoustic analysis, apply the fluid-structure interaction flag (Label = FSI) to only the FLUID129 or FLUID130 elements.

valuestr

Surface load value or table name reference for specifying tabular boundary conditions.

If Lab = CONV:

  • VALUE is typically the film coefficient and VALUE2 (below) is typically the bulk temperature. If Lab = CONV and VALUE = - N, the film coefficient may be a function of temperature and is determined from the HF property table for material N ( mp ). (See the scopt command for a way to override this option and use - N as the film coefficient.) The temperature used to evaluate the film coefficient is usually the average between the bulk and wall temperatures, but may be user-defined for some elements.

  • If kbc,0 has been issued for ramped loads, it affects only VALUE2, the bulk temperature, and the film coefficient specification is unaffected.

If Lab = RAD, VALUE is the surface emissivity.

If Lab = PORT, VALUE is a port number representing a waveguide exterior port. The port number must be an integer between 1 and 50. For acoustic 2×2 transfer admittance matrix, the port number can be any positive integer. The smaller port number corresponds to the port 1 of the 2×2 transfer admittance matrix and the greater port number corresponds to the port 2. If one port of the transfer admittance matrix is connecting to the acoustic-structural interaction interface, the port number corresponds to the port 2 of the transfer admittance matrix. A pair of ports of the 2×2 transfer admittance matrix must be defined in the same element.

If Lab = SHLD, VALUE is the surface normal velocity in harmonic analysis and the surface normal acceleration in transient analysis for acoustics.

If Lab = IMPD, VALUE is resistance in (N)(s)/m 3 if VALUE > 0 and is conductance in mho if VALUE < 0 for acoustics. In acoustic transient analyses, VALUE2 is not used.

If Lab = RDSF, VALUE is the emissivity value; the following conditions apply: If VALUE is between 0 and 1, apply a single value to the surface. If VALUE = - N, the emissivity may be a function of the temperature, and is determined from the EMISS property table for material N ( mp ). The material N does not need to correlate with the underlying solid thermal elements.

If Lab = FSIN in a unidirectional Mechanical APDL to CFX analysis, VALUE is not used.

If Lab = ATTN, VALUE is the absorption coefficient of the surface.

value2str

Second surface load value (if any).

If Lab = CONV:

  • VALUE2 is typically the bulk temperature for thermal analyses.

  • If kbc,0 has been issued for ramped loads, the bulk temperature is ramped from the value defined by tunif to the value specified by VALUE2 for the first loadstep. If tabular boundary conditions are defined, the kbc command is ignored and tabular values are used.

  • For acoustic analyses, VALUE2 is not used.

If Lab = RAD VALUE2 is ambient temperature.

If Lab = SHLD, VALUE2 is the phase angle of the normal surface velocity (defaults to zero) for harmonic response analyses while VALUE2 is not used for transient analyses in acoustics.

If Lab = IMPD, VALUE2 is reactance in (N)(s)/m 3 if VALUE > 0 and is the product of susceptance and angular frequency if VALUE < 0 for acoustics.

If Lab = RDSF, VALUE2 is the enclosure number. Radiation will occur between surfaces flagged with the same enclosure numbers. If the enclosure is open, radiation will also occur to ambient. If VALUE2 is negative, radiation direction is reversed and will occur inside the element for the flagged radiation surfaces.

If Lab = FSIN in a unidirectional Mechanical APDL to CFX analysis, VALUE2 is the surface interface number (not available from within the GUI).

Notes

Surface loads may be transferred from areas to elements with the sftran or sbctran commands. See the sfgrad command for an alternate tapered load capability.

Tabular boundary conditions Tabular boundary conditions ( VALUE = tabname and/or VALUE2 = tabname) are available for the following surface load labels ( Lab ) only: PRES (real and/or imaginary components), CONV (film coefficient and/or bulk temperature) or HFLUX, and RAD (surface emissivity and ambient temperature). Use the dim command to define a table.

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.