4.22 SURF22 3-D Surface Effect

Figure 4.22-1 SURF22 3-D Surface Effect Element

4.22.1 Input Data

The element thicknesses (real constants TKI, TKJ, TKK, TKL) are used in the mass, volume, and heat generation calculations. Thicknesses TKJ, TKK, and TKL default to TKI, which defaults to 1.0. The density (material property DENS) is used in the mass calculation. The in-plane force per unit length (input as real constant SURT) and the elastic foundation stiffness (input as real constant EFS) are used in the stiffness matrix calculation. A damping surface can be input as the product of an extremely low value of the elastic foundation stiffness (EFS) and an equivalently high value of the material damping (MP,DAMP). This is useful for non-reflective boundary conditions.

Element loads are described in Section 2.7. Pressures, convections, or heat fluxes may be input as surface loads on the element faces as shown by the circled numbers on Figure 4.22-1. The pressure value is used in the pressure load vector calculation. For the first four faces, positive values of pressure act in the positive element coordinate directions (except for the normal pressure which acts in the negative z direction). For faces 1 and 4, positive or negative values may be removed as requested with KEYOPT(6) to simulate the discontinuity at the free surface of a contained fluid. For face 4, the magnitude of the pressure at each integration point is P_I + XP_J + YP_K + ZP_L, where P_I through P_L are input as VAL1 through VAL4 on the SFE command, and X,Y,Z are the global Cartesian coordinates at the current location of the point. For face 5, the magnitude of the pressure is P_I, and the direction is . The load may be adjusted with KEYOPTs(11) and (12).

The film coefficient (input on the SFE command with KVAL=0 and CONV as the label) is used in the convection surface conductivity matrix calculation. If the extra node is used, its temperature is used as the bulk temperature. If the extra node is not used, the CONV value input with KVAL=2 is used as the bulk temperature. The bulk temperature is used in the convection surface heat flow vector calculation. On a given face, either a heat flux or a convection may be specified, but not both simultaneously.

Temperatures and heat generation rates may be input as element body loads at the nodes. Heat generation rates are input on a per unit volume basis. Element body load temperatures are not applied to other elements connected at the same nodes. The node I temperature T(I) defaults to TUNIF. If all other temperatures are unspecified, they default to T(I). If all corner node temperatures are specified, each midside node temperature defaults to the average temperature of its adjacent corner nodes. For any other input temperature pattern, unspecified temperatures default to TUNIF. Similar defaults occur for heat generation rates except that zero is used instead of TUNIF. Temperatures are used for material property evaluation only. The heat generation rate values are used in the heat generation load vector calculation.

SURF22 allows for radiation between the surface and the extra node. The emissivity of the surface (input as material property EMIS for the material number of the element) is used for the radiation surface conductivity matrix. The form factor FORMF and the Stefan-Boltzmann constant SBCONST are also used for the radiation surface conductivity matrix. The form factor may be input as a real constant (defaults to 1) using KEYOPT(9)=1, or a cosine effect may be calculated (using KEYOPT(9)=2 or 3) from the basic element orientation and the extra node location. (See Section 14.22 of the ANSYS Theory Reference for details.) There is no distance effect included in the cosine effect. The Stefan-Boltzmann constant defaults to 0.119x10^-10 (BTU/hr*in²*°R⁴)).

When KEYOPT(4)=0, midside nodes may be dropped. See Section 2.4.2 of the ANSYS Modeling and Meshing Guide for information on the use of elements with midside nodes.

A summary of the element input is given in Table 4.22-1. Section 2.1 gives a general description of element input.

Table 4.22-1 SURF22 Input Summary

Element Name	SURF22
Nodes	I, J, K, L if KEYOPT (4) = 1 and KEYOPT (5) = 0 I, J, K, L, M if KEYOPT (4) = 1 and KEYOPT (5) = 1 I, J, K, L, M, N, O, P if KEYOPT (4) = 0 and KEYOPT (5) = 0 I, J, K, L, M, N, O, P, Q if KEYOPT (4) = 0 and KEYOPT (5) = 1
Degrees of Freedom	UX, UY, UZ if KEYOPT(1) = 0 TEMP if KEYOPT(1) = 1 UX, UY, UZ, TEMP if KEYOPT(1) = 2
Real Constants	FORMF, SBCONST, (Blank), EFS, SURT, (Blank), TKI, TKJ, TKK, TKL
Material Properties	DENS (for density) EMIS (for emissivity, if KEYOPT(9) > 0) DAMP (for damping, with EFS; see Input Data section for details)
Surface Loads	Pressures: face 1 (I-J-K-L) (in -z normal direction), face 2 (I-J-K-L) (tangential (+x)) face 3 (I-J-K-L) (tangential (+y)) face 4 (I-J-K-L) (in -z normal direction, global taper) face 5 (I-J-K-L) (oriented by input vector) Convections: face 1 (I-J-K-L) if KEYOPT (8) >1 Heat Fluxes face 1 (I-J-K-L) if KEYOPT (8) = 1
Body Loads	Temperatures: T (I), T ( J ), T ( K ), T( L ), and, if KEYOPT (4) = 0, T( M ), T( N ), T( O ), T(P) Heat Generation: HG ( I ), HG ( J ), HG ( K ), HG ( L ), and, if KEYOPT ( 4 ) = 0, HG ( M ), HG ( N ), HG ( O ), HG (P)
Special Features	Stress stiffening, Large deflection, Birth and death
KEYOPT(1)	Selects degrees of freedom: 0 - UX, UY, UZ 1 - TEMP 2 - UX, UY, UZ, TEMP
KEYOPT(4)	0 - Has midside nodes (that match the adjacent solid element) 1 - Does not have midside nodes
KEYOPT(5)	0 - No extra node 1 - Has extra node (optional if KEYOPT (8) >1; required if KEYOPT (9) > 0)
KEYOPT(6)	Applicable only to normal direction pressure (faces 1 and 4): 0 - Use pressures as calculated (positive and negative) 1 - Use positive pressures only (negative set to zero) 2 - Use negative pressures only (positive set to zero)
KEYOPT(8)	0 - Ignore heat flux and convection surface loads (if any) 1 - Include heat flux, ignore convection Use the following to include convection (ignore heat flux): 2 - Evaluate film coefficient hf (if any) at average film temperature, (TS +TB)/2 3 - Evaluate hf at element surface temperature, TS 4 - Evaluate hf at fluid bulk temperature, TB 5 - Evaluate hf at differential temperature, | TS - TB |
KEYOPT(9)	0 - Do not include radiation 1 - Use radiation with the form factor real constant 2 - Use radiation with cosine effect calculated as an absolute value (ignore real constant) 3 - Use radiation with cosine effect calculated as zero if negative (ignore real constant)
KEYOPT(11)	Pressure applied by vector orientation (face 5): 0 - On projected area and includes tangential component 1 - On projected area and does not include tangential component 2 - On full area and includes the tangential component
KEYOPT(12)	Effect of the direction of the element normal (element z-axis) on vector oriented (face 5) pressure: 0 - Pressure load is applied regardless of the element normal orientation 1 - Pressure load is not used if the element normal is oriented in the same general direction as the pressure vector.

4.22.2 Output Data

• nodal degree of freedom results included in the overall nodal solution
• additional element output as shown in Table 4.22-2.

The following notation is used in Table 4.22-2:

A colon (:) in the Name column indicates the item can be accessed by the Component Name method [ETABLE, ESOL] (see Section 2.2.2). The O and R columns indicate the availability of the items in the file Jobname.OUT (O) or in the results file (R), a Y indicates that the item is always available, a number refers to a table footnote which describes when the item is conditionally available, and a - indicates that the item is not available.

Table 4.22-2 SURF22 Element Output Definitions

Name	Definition	O	R
EL	Element number	Y	Y
SURFACE NODES	Nodes - I, J, K, L	Y	Y
EXTRA NODE	Extra node (if present)	Y	Y
MAT	Material number	Y	Y
AREA	Surface area	Y	Y
VOLU:	Volume	Y	Y
CENT: X, Y, Z	Center location XC, YC, ZC	-	Y
VN(X,Y,Z)	Components of unit vector normal to center of element	-	Y
EP	Membrane strains (EPX, EPY, EPXY) in the element coordinate system	1	1
PRES	Pressures P1, P2, P3, P4, P5 at nodes I, J, K, L	2	2
DVX, DVY, DVZ	Direction vector of pressure P5	2	2
AVG. FACE PRESSURE	Average normal pressure (P1AVG) Average tangential-X pressure (P2AVG) Average tangential-Y pressure (P3AVG) Average tapered normal pressure (P4AVG) Effective value of vector oriented pressure (P5EFF)	2	2
TEMP	Surface temperatures T(I), T(J), T(K), T(L), T(M), T(N), T(O), T(P)	3	3
DENSITY	Density	4	4
MASS	Mass of element	4	4
FOUNDATION STIFFNESS	Foundation Stiffness (input as EFS)	5	5
SURFACE TENSION	Surface Tension (input as SURT)	6	6
HGEN	Heat generations HG(I), HG(J), HG(K), HG(L), HG(M), HG(N), HG(O), HG(P)	7	7
HEAT GEN. RATE	Heat generation rate over entire element (HGTOT)	7	7
HFLUX	Heat flux at nodes I, J, K, L	8	-
HEAT FLOW RATE	Heat flow rate over element surface area (HFCTOT)	8	8
HFILM	Film coefficient at each face node	9	9
TBULK	Bulk temperature at each face node or temperature of extra node	9	9
TAVG	Average surface temperature	9	9
CONV. HEAT RATE	Convection heat flow rate over element surface area (HFCTOT)	9	9
CONV. HEAT RATE/AREA	Average convection heat flow rate per unit area	9	-
EMISSUR	Average emissivity of surface (for element material number)	10	10
TEMPSUR	Average temperature of surface	10	10
TEMPEXT	Temperature of extra node	10	10
FORM FACTOR	Average form factor of element	10	10
RAD. HEAT RATE	Radiation heat flow rate over entire element (HRTOT)	10	10
RAD. HEAT RATE/AREA	Average radiation heat flow rate per unit area	10	-

1. If KEYOPT(1)=0 or 2

2. If KEYOPT(1)=0 or 2 and pressure load

3. If KEYOPT(1)=0 and temperature load

4. If KEYOPT(1)=0 or 2 and DENS>0

5. If KEYOPT(1)=0 or 2 and EFS>0

6. If KEYOPT(1)=0 or 2 and SURT>0

7. If KEYOPT(1)=1 or 2 and heat generation load

8. If KEYOPT(1)=1 or 2 and KEYOPT(8)=1

9. If KEYOPT(1)=1 or 2 and KEYOPT(8)>1

10. If KEYOPT(1)=1 or 2 and KEYOPT(9)>0

Table 4.22-3 lists output available through the ETABLE command using the Sequence Number method. See Chapter 5 of the ANSYS Basic Analysis Procedures Guide and Section 2.2.2.2 of this manual for more information. The following notation is used in Table 4.22-3:

Name - output quantity as defined in the Table 4.22-2

Item - predetermined Item label for ETABLE command

E - sequence number for single-valued or constant element data

I,J,K,L - sequence number for data at nodes I,J,K,L

Name	Item	E	I	J	K	L
P1	SMISC	-	1	2	3	4
P2	SMISC	-	5	6	7	8
P3	SMISC	-	9	10	11	12
P4	SMISC	-	22	23	24	25
P5	SMISC	26	-	-	-	-
P1AVG	SMISC	13	-	-	-	-
P2AVG	SMISC	14	-	-	-	-
P3AVG	SMISC	15	-	-	-	-
P4AVG	SMISC	30	-	-	-	-
P5EFF	SMIC	31	-	-	-	-
DVX	SMISC	27	-	-	-	-
DVY	SMISC	28	-	-	-	-
DVZ	SMISC	29	-	-	-	-
EPX	SMISC	16	-	-	-	-
EPY	SMISC	17	-	-	-	-
EPXY	SMISC	18	-	-	-	-
HGTOT	SMISC	19	-	-	-	-
HFCTOT	SMISC	20	-	-	-	-
HRTOT	SMISC	21	-	-	-	-
DENS	NMISC	1	-	-	-	-
MASS	NMISC	2	-	-	-	-
EFS	NMISC	3	-	-	-	-
SURT	NMISC	4	-	-	-	-
HFILM	NMISC	5	-	-	-	-
TAVG	NMISC	6	-	-	-	-
TBULK	NMISC	7	-	-	-	-
EMISSUR	NMISC	8	-	-	-	-
TEMPSUR	NMISC	10	-	-	-	-
TEMPEXT	NMISC	11	-	-	-	-
FORM FACTOR	NMISC	12	-	-	-	-
AREA	NMISC	15	-	-	-	-
VNX	NMISC	16	-	-	-	-
VNY	NMISC	17	-	-	-	-
VNZ	NMISC	18	-	-	-	-

4.22.3 Assumptions and Restrictions

• The element must not have a zero area.
• The surface tension load vector acts in the plane of the element as a constant force applied to the nodes seeking to minimize the area of the surface.
• For structural large deflection analyses, the loads are applied to the current size of the element, not the initial size.
• If KEYOPT(9)>0, the element is nonlinear and requires an iterative solution. Also, the extra node must be present.
• Surface printout is not valid for elements deactivated [EKILL] and then reactivated [EALIVE]. Surface printout does not include large strain effects.
• Due to the rotations not being included, SURF22 may not be used to apply pressure loads to SOLID72 or SOLID73.

4.22.4 Product Restrictions

ANSYS/Structural

• This element has only the structural capabilities (no Thermal).
• Only active DOFs are UX, UY, UZ. KEYOPT(1)=0.
• KEYOPT(5, 8, 9) are NOT applicable.
• The only allowable material property is DENS.
• The connection with the flux surface loads are not applicable.

• This element has only thermal capability and does not have structural capability.
• The only active degree of freedom is TEMP. KEYOPT(1) defaults to 1 instead of 0 and cannot be changed.
• KEYOPT(6) is not applicable.
• The only allowable material property is EMIS.
• Pressure surface loads and temperature body loads are not applicable.
• No special features are allowed.