SFE, Elem, LKEY, Lab, KVAL, VAL1, VAL2, VAL3, VAL4
Specifies surface loads on elements.

Compatible Products: – | Pro | Premium | Enterprise | Ent PP | Ent Solver | –


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.


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.


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

DisciplineSurface Load LabelLabel Description
FREQFrequency (harmonic analyses only)
HFLUX[1]Heat flux
RDSFSurface-to-surface radiation
Fluid FSI[2]Fluid-structure interaction flag
IMPDImpedance boundary flag
ElectricCHRGSSurface charge density
MXWFMaxwell force flag
MagneticMXWFMaxwell force flag
Acoustic fluid


Fluid-structure interaction flag
IMPDImpedance or admittance coefficient
SHLDSurface normal velocity or acceleration
MXWFMaxwell surface flag or equivalent source surface
FREEFree surface flag
INFExterior Robin radiation boundary flag
PORTPort number
ATTNAttenuation coefficient
BLIViscous-thermal boundary layer surface flag
Field-surface interfaceFSINField-surface interface number
PoromechanicsFFLXFluid flow flux
Infinite elementINFExterior surface flag for INFIN110 and INFIN111
SubstructureSELV[3]Load vector number
DiffusionDFLUXDiffusion flux
  1. Thermal labels CONV and HFLUX are mutually exclusive.

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

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


Value key. If Lab = PRES:

0 or 1


VAL1 through VAL4 are used as real components of pressures.



VAL1 through VAL4 are used as imaginary components of pressures.

Value key. If Lab = CONV:

0 or 1


For thermal analyses, VAL1 through VAL4 are used as the film coefficients.



For thermal analyses, VAL1 through VAL4 are the bulk temperatures.



VAL1 through VAL4 are used as film effectiveness.



VAL1 through VAL4 are used as free stream temperature.

Value key. If Lab = SHLD:

0 or 1


For acoustics, VAL1 through VAL4 are used as the normal velocity (harmonic) or normal acceleration (transient).



For acoustics, VAL1 through VAL4 are used as the phase angle for harmonic response analyses.

Value key. If Lab = RAD:

0 or 1


VAL1 through VAL4 are used as the emissivities.



VAL1 through VAL4 are ambient temperatures.

Value key. If Lab = RDSF:

0 or 1


VAL1 is the emissivity value between 0 and 1.



VAL1 is the enclosure number.

Value key. If Lab = SELV:

0 or 1


VAL1 is the multiplier on real load vector LKEY.



VAL1 is the multiplier on imaginary load vector LKEY.

Value key. If Lab = IMPD:

0 or 1


For acoustic harmonic analyses, VAL1 through VAL4 are used as the real part of the impedance.



For acoustic harmonic analyses, VAL1 through VAL4 are used as the imaginary part of the impedance.

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


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 VAL1 then applies to node J of face 1. To specify a table, enclose the table name in percent signs (%), e.g., %tabname%. Use the *DIM command to define a table. Only one table can be specified, and it must be specified in the VAL1 position; tables specified in the VAL2, VAL3, or VAL4 positions will be ignored. VAL2 applies to node I, etc.

If Lab = PRES and KVAL = 2, VAL1 is the imaginary pressure, which is used only by SURF153, SURF154, SURF156, or SURF159 in full harmonic analyses (HROPT,FULL), or by a mode-superposition harmonic analysis (HROPT,MSUP) if the mode-extraction method is Block Lanczos (MODOPT,LANB), PCG Lanczos (MODOPT,LANPCG), Supernode (MODOPT,SNODE), or Subspace (MODOPT,SUBSP).

If Lab = CONV, KVAL = 0 or 1, and VAL1 = -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 = PORT, VAL1 is a port number representing a waveguide 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 = RDSF, KVAL = 0 or 1, and VAL1 = -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 VAL1 is negative, radiation direction is reversed and will occur inside the element for the flagged radiation surfaces.

If Lab = FSIN in a Multi-field solver (single or multiple code coupling) analysis, VAL1 is the surface interface number. KVAL is not used. If Lab = FSIN in a unidirectional ANSYS-to-CFX analysis, VAL1 is not used unless the ANSYS analysis is performed using the Multi-field solver.

If Lab = SELV, VAL1 represents the scale factor (default = 0.0).

If Lab = ATTN, VAL1 is the attenuation coefficient.


Surface load values at the 2nd, 3rd, and 4th nodes (if any) of the face. If all three values are blank, all three default to VAL1, giving a constant load. Zero or other blank values are used as zero. If a table is specified in VAL1, then any tables or numerical values specified in VAL2, VAL3, or VAL4 will be ignored.

If Lab = FSIN in a unidirectional ANSYS to CFX analysis, VAL2 is the surface interface number (not available from within the GUI). VAL3 and VAL4 are not used.


Specifies surface loads on selected elements.

Caution:  You cannot use the SFE command with the INFIN110 or INFIN111 elements without prior knowledge of element face orientation, i.e., you must know which face is the exterior in order to flag it. Also, the surface effect elements, SURF153 and SURF154, use LKEY to allow the use of tangential and other loads (see SURF153and SURF154 of the Element Reference for more details).

Tapered loads may be applied over the faces of most elements.

For beam elements allowing lateral surface loads that may be offset from the nodes, use the SFBEAM command to specify the loads and offsets. See the SF command for an alternate surface load definition capability based upon node numbers. See the SFGRAD command for an alternate tapered load capability. Use the SFCUM command to accumulate (add) surface loads applied with SFE.

The SFE command can also be used to define fluid pressure penetration loads (Lab = PRES) at a contact interface. For this type of load, LKEY = 1 is used to specify the pressure values and LKEY = 2 is used to specify starting points and penetrating points. See Applying Fluid Penetration Pressure in the Contact Technology Guide for details on how to apply this type of load.

Film effectiveness and free stream temperatures specified with Lab = CONV are only valid 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 on film effectiveness, see Conduction and Convection in the Mechanical APDL Theory Reference.

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), attenuation 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.

This command is also valid in PREP7 and in the /MAP processor.

Menu Paths

Main Menu>Preprocessor>Loads>Define Loads>Apply>Electric>Excitation>AppSurfChar>On Elements
Main Menu>Preprocessor>Loads>Define Loads>Apply>Field Surface Intr>On Elements
Main Menu>Preprocessor>Loads>Define Loads>Apply>Fluid/ANSYS>Impedance>On Elements
Main Menu>Preprocessor>Loads>Define Loads>Apply>Load Vector>For Superelement
Main Menu>Preprocessor>Loads>Define Loads>Apply>Structural>Pressure>On Element Components
Main Menu>Preprocessor>Loads>Define Loads>Apply>Structural>Pressure>On Elements
Main Menu>Preprocessor>Loads>Define Loads>Apply>Thermal>Convection>On Elements>Tapered
Main Menu>Preprocessor>Loads>Define Loads>Apply>Thermal>Convection>On Elements>Uniform
Main Menu>Preprocessor>Loads>Define Loads>Apply>Thermal>Heat Flux>On Elements
Main Menu>Preprocessor>Loads>Define Loads>Apply>Thermal>Radiation>On Elements
Main Menu>Solution>Define Loads>Apply>Electric>Excitation>AppSurfChar>On Elements
Main Menu>Solution>Define Loads>Apply>Field Surface Intr>On Elements
Main Menu>Solution>Define Loads>Apply>Fluid/ANSYS>Impedance>On Elements
Main Menu>Solution>Define Loads>Apply>Load Vector>For Superelement
Main Menu>Solution>Define Loads>Apply>Structural>Pressure>On Element Components
Main Menu>Solution>Define Loads>Apply>Structural>Pressure>On Elements
Main Menu>Solution>Define Loads>Apply>Thermal>Convection>On Elements>Tapered
Main Menu>Solution>Define Loads>Apply>Thermal>Convection>On Elements>Uniform
Main Menu>Solution>Define Loads>Apply>Thermal>Heat Flux>On Elements
Main Menu>Solution>Define Loads>Apply>Thermal>Radiation>On Elements
The SFE,,,ATTN command cannot be accessed from a menu.

Release 18.2 - © ANSYS, Inc. All rights reserved.