sfe#

FeSurfaceLoads.sfe(elem='', lkey='', lab='', kval='', value1='', value2='', value3='', value4='', meshflag='', **kwargs)#

Defines surface loads on elements.

Mechanical APDL Command: SFE

Parameters:
elemstr

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

lkeystr

Load key or face number 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.

If you issue sfcontrol before sfe, LKEY is the face number for supported structural solid and shell elements.

labstr

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

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

documentation pointed above.

Thermal labels CONV and HFLUX are mutually exclusive.

For an acoustic analysis, apply the fluid-structure interaction flag (Label = FSI) to only the FLUID29, FLUID30, FLUID220, and FLUID221 elements.

When a load vector exists for a thermal superelement, it must be applied and have a scale factor of 1 ( sfe,,,SELV,,1).

kvalint or str

Value key. If Lab = PRES:

  • 0 or 1 - VALUE1 through VALUE4 are used as real components of pressures.

  • 2 - VALUE1 through VALUE4 are used as imaginary components of pressures.

Value key. If Lab = CONV:

  • 0 or 1 - For thermal analyses, VALUE1 through VALUE4 are used as the film coefficients.

  • 2 - For thermal analyses, VALUE1 through VALUE4 are the bulk temperatures.

  • 3 - VALUE1 through VALUE4 are used as film effectiveness.

  • 4 - VALUE1 through VALUE4 are used as free stream temperature.

Value key. If Lab = RAD:

  • 0 or 1 - VALUE1 through VALUE4 are used as the emissivities.

  • 2 - VALUE1 through VALUE4 are ambient temperatures.

Value key. If Lab = RDSF:

  • 0 or 1 - VALUE1 is the emissivity value between 0 and 1.

  • 2 - VALUE1 is the enclosure number.

Value key. If Lab = IMPD:

  • 0 or 1 - For acoustic harmonic analyses, VALUE1 through VALUE4 are used as the real part of the impedance.

  • 2 - For acoustic harmonic analyses, VALUE1 through VALUE4 are used as the imaginary part of the impedance.

Value key. If Lab = SHLD:

  • 0 or 1 - For acoustic analyses, VALUE1 through VALUE4 are used as the normal velocity (harmonic) or normal acceleration (transient).

  • 2 - For acoustic analyses, VALUE1 through VALUE4 are used as the phase angle for harmonic response analyses.

Value key. If Lab = ATTN:

  • 0 or 1 - For acoustic analyses, VALUE1 through VALUE4 are used as the absorption coefficient of the surface.

  • 2 - For acoustic analyses, VALUE1 through VALUE4 are used as the transmission loss (dB) of the coupled wall in an energy diffusion solution for room acoustics.

Value key. If Lab = SELV:

  • 0 or 1 - VALUE1 is the multiplier on real load vector LKEY.

  • 2 - VALUE1 is the multiplier on imaginary load vector LKEY.

If only one set of data is supplied, the other set of data defaults to previously specified values (or zero if not previously specified) in the all of the following cases:

  • Emissivities are supplied and Lab = RAD

  • Temperatures are supplied and Lab = RAD

  • Temperatures are supplied and Lab = CONV

  • Film coefficients are supplied and Lab = CONV

  • Normal velocity/acceleration for acoustics is supplied and Lab = SHLD

  • Phase angle for acoustics is supplied and Lab = SHLD

value1str

First surface load value (typically at the first node of the face), or the name of a table for specifying tabular boundary conditions.

Face nodes are listed in the order given for Surface Loads in the input data table for each element type in the Element Reference. For example, for SOLID185, the item 1-JILK associates LKEY = 1 (face 1) with nodes J, I, L, and K. Surface load value VALUE1 then applies to node J of face 1. To specify a table, enclose the table name in percent signs (%), for example, tabname. Use the dim command to define a table. Only one table can be specified, and it must be specified in the VALUE1 position; tables specified in the VALUE2, VALUE3, or VALUE4 positions are ignored. VALUE2 applies to node I, etc.

If Lab = PRES and KVAL = 2, this value is the imaginary pressure component, used by the following supported elements:

  • Surface elements: SURF153, SURF154 and SURF159.

  • Solid and solid-shell elements: PLANE182, PLANE183, SOLID185, SOLID186, SOLID187, SOLSH190, and SOLID285.

  • Shell elements: SHELL181, SHELL281, SHELL208, and SHELL209.

  • Coupled-field elements with structural degrees of freedom: PLANE222, PLANE223, SOLID225, SOLID226, and SOLID227.

If Lab = CONV, KVAL = 0 or 1, and VALUE1 = - N, the film coefficient is assumed to 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 Lab = CONV, KVAL = 2, VALUE1 specifies the bulk temperature. If kbc,0 has been issued for ramped loads, the bulk temperature is ramped from the value defined by tunif to that specified on VALUE1 (for the first loadstep). If a table name is specified for VALUE1, the kbc command is ignored and tabular values are used.

If Lab = PORT, VALUE1 is a port number representing a waveguide port. The port number must be an integer between 1 and 50. For an acoustic 2×2 transfer admittance matrix, the port number can be any positive integer. The smaller port number corresponds to port 1 of the 2×2 transfer admittance matrix, and the greater port number corresponds to port 2. If one port of the transfer admittance matrix is connecting to the acoustic-structural interaction interface, the port number corresponds to 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 = RDSF, KVAL = 0 or 1, and VALUE1 = - N, the emissivity is assumed to 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 = RDSF, KVAL = 2, and VALUE1 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, VALUE1 is not used.

If Lab = SELV, VALUE1 represents the scale factor (default = 0.0).

If Lab = ATTN, VALUE1 is the absorption coefficient.

value2str

Surface load values at the second, third, and fourth nodes (if any) of the face.

If all three values are blank, all default to VALUE1, giving a constant load. Zero or other blank values are used as zero.

If VALUE2, VALUE3, or VALUE4 are magnitudes of the load, they are ignored if VALUE1 is a table. If VALUE2, VALUE3, or VALUE4 are any other values, they are used even if VALUE1 is a table (for example, the load direction for face 5 of SURF154 ).

If Lab = FSIN in a unidirectional Mechanical APDL-to-CFX analysis, VALUE2 is the surface interface number (not available in the GUI). VALUE3 and VALUE4 are not used.

value3str

Surface load values at the second, third, and fourth nodes (if any) of the face.

If all three values are blank, all default to VALUE1, giving a constant load. Zero or other blank values are used as zero.

If VALUE2, VALUE3, or VALUE4 are magnitudes of the load, they are ignored if VALUE1 is a table. If VALUE2, VALUE3, or VALUE4 are any other values, they are used even if VALUE1 is a table (for example, the load direction for face 5 of SURF154 ).

If Lab = FSIN in a unidirectional Mechanical APDL-to-CFX analysis, VALUE2 is the surface interface number (not available in the GUI). VALUE3 and VALUE4 are not used.

value4str

Surface load values at the second, third, and fourth nodes (if any) of the face.

If all three values are blank, all default to VALUE1, giving a constant load. Zero or other blank values are used as zero.

If VALUE2, VALUE3, or VALUE4 are magnitudes of the load, they are ignored if VALUE1 is a table. If VALUE2, VALUE3, or VALUE4 are any other values, they are used even if VALUE1 is a table (for example, the load direction for face 5 of SURF154 ).

If Lab = FSIN in a unidirectional Mechanical APDL-to-CFX analysis, VALUE2 is the surface interface number (not available in the GUI). VALUE3 and VALUE4 are not used.

meshflagstr

Specifies how to apply normal pressure loading on the mesh. Valid in a nonlinear adaptivity analysis when Lab = PRES and KVAL = 0 or 1.

0 - Pressure loading occurs on the current mesh (default).

1 - Pressure loading occurs on the initial mesh for nonlinear adaptivity.

Notes

sfe defines surface loads on selected elements.

Warning

You cannot use sfe with the INFIN110 or INFIN111 elements without prior knowledge of element-face orientation (that is, you must know which face is the exterior in order to flag it). Also, for surface-effect elements SURF153 and SURF154, use LKEY to enable tangential and other loads. For supported structural solid and shell elements, issue sfcontrol to define tangential and other loads.

sfe can apply tapered loads over the faces of most elements.

You can use these related surface-load commands with sfe :

  • sf - Defines surface loads on nodes.

  • sfbeam - For beam elements allowing lateral surface loads that can be offset from the nodes, this command specifies the loads and offsets.

  • sfcontrol - Applies general (normal, tangential, and other) surface loads to supported structural elements.

  • sfcum - Accumulates (adds) surface loads applied via sfe.

  • sfdele - Delete loads applied via sfe.

  • sffun - Applies loads from a node-vs.-value function.

  • sfgrad - Applies an alternate tapered load.

The sfe command can also define fluid-pressure-penetration loads ( Lab = PRES) at a contact interface. For this type of load, LKEY = 1 is used to specify the normal pressure values, LKEY = 3 is used to specify the tangential pressure values along the x direction of esys, LKEY = 4 is used to specify the tangential pressure values along the y direction of esys, and LKEY = 2 is used to specify starting points and penetrating points. See Applying Fluid Penetration Pressure

Film effectiveness and free-stream temperatures specified via Lab = CONV are valid only for SURF151 and SURF152. Film effectiveness must be between 0 and 1 and it defaults to 0. If film effectiveness is applied, bulk temperature is ignored. When film effectiveness and free stream temperatures are specified, the commands to specify a surface-load gradient ( sfgrad ) or surface-load accumulation ( sfcum ) are not valid. For more information about film effectiveness, see Conduction, Convection, and Mass Transport (Advection)

You can specify a table name only when using structural (PRES) and thermal (CONV [film coefficient, bulk temperature, film effectiveness, and free stream temperature], HFLUX), diffusion flux (DFLUX), surface emissivity and ambient temperature (RAD), impedance (IMPD), normal velocity or acceleration (SHLD), absorption coefficient (ATTN), and substructure (SELV) surface load labels.

When a tabular function load is applied to an element, the load will not vary according to the positioning of the element in space.

For cases where Lab=FSI, MXWF, FREE, and INF, VALUE is not needed.

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 the PREP7 and slashmap processors.