Problems with esel

- March 10, 2023 at 12:17 pm
  
  John Miller
  Subscriber
  
  Hello together,
  
  I’m struggling a little bit with the element selection of in /prep7-created thermal surface elements.
  The model is really simple a cube with convection load at the surfaces, except the top surface.
  
  Model:
  Cube 10 mm x 10 mm x 10 mm
  208 nodes
  40 nodes on the top surface
  27 elements
  148 nodes at the exterior surface, except the top surface (I know the corner nodes)
  And 9 elements contain the nodes of the top surface
  The code for the creation of surf152 elements looks like:
  /prep7
  /GOPR
  /com,*********************Start surf152*********************
     nsel,none
     esel,none
     esel,s,ename,,surf152         ! Element selection of surf152 elements
     nsel,stat
     esel,stat
     cm,ELsurf152,elements         ! Create a component which includes surf152 elements
     nsel,stat
     esel,stat
     edele,ELsurf152               ! Deletion of former surf152 elements
     nsel,stat
     esel,stat
     et,100,152,,,,,0              ! KEYOPT(5) = 0, No extra nodes.
     cmsel,s,external,node         ! Select nodes for esurf
     nsel,stat
     esel,stat
     esln,s,0                      ! Select the elements of the selected nodes
     nsel,stat
     esel,stat
     type,100                      ! Asign element type 100
     esurf                         ! Surface Elements generation
     nsel,stat
     esel,stat
     allsel,all
  /com,*********************Ende surf152*********************
  /solu
  
  And the corresponding solver output is:
            ***** ANSYS ANALYSIS DEFINITION (PREP7) *****
  *********************Start surf152*********************
  
  NONE SELECT FOR ITEM=NODE COMPONENT=
  IN RANGE         1 TO        208 STEP          1
  
            0 NODES (OF        208 DEFINED) SELECTED BY NSEL COMMAND.
  
  NONE SELECT FOR ITEM=ELEM COMPONENT=
  IN RANGE         1 TO        126 STEP          1
  
            0 ELEMENTS (OF         72 DEFINED) SELECTED BY ESEL COMMAND.
  
  SELECT       FOR ITEM=ENAM COMPONENT=
  IN RANGE       152 TO        152 STEP          1
  
           45 ELEMENTS (OF         72 DEFINED) SELECTED BY ESEL COMMAND.
  
  ****** STATUS OF NODES ******
  NUMBER OF SELECTED NODES=         0
  NUMBER OF DEFINED NODES=        208
  MAXIMUM NODE NUMBER=            208
  
  ****** STATUS OF ELEMENTS ******
  NUMBER OF SELECTED ELEMENTS=        45
  NUMBER OF DEFINED ELEMENTS=         72
  MAXIMUM ELEMENT NUMBER=            126
  
  DEFINITION OF COMPONENT = ELSURF152 ENTITY=ELEM
  
  ****** STATUS OF NODES ******
  NUMBER OF SELECTED NODES=         0
  NUMBER OF DEFINED NODES=        208
  MAXIMUM NODE NUMBER=            208
  
  ****** STATUS OF ELEMENTS ******
  NUMBER OF SELECTED ELEMENTS=        45
  NUMBER OF DEFINED ELEMENTS=         72
  MAXIMUM ELEMENT NUMBER=            126
  
  *** WARNING ***                         CP =       0.547   TIME= 11:00:35
  Assembly ELSURF152 is deleted.
  
  ****** STATUS OF NODES ******
  NUMBER OF SELECTED NODES=         0
  NUMBER OF DEFINED NODES=        208
  MAXIMUM NODE NUMBER=            208
  
  ****** STATUS OF ELEMENTS ******
  NUMBER OF SELECTED ELEMENTS=         0
  NUMBER OF DEFINED ELEMENTS=         27
  MAXIMUM ELEMENT NUMBER=            126
  
  ELEMENT TYPE        100 IS SURF152      3-D THERMAL SURFACE
  KEYOPT( 1- 6)=        0      0      0        0      0      0
  KEYOPT( 7-12)=        0      0      0        0      0      0
  KEYOPT(13-18)=        0      0      0        0      0      0
  
  CURRENT NODAL DOF SET IS TEMP
  THREE-DIMENSIONAL MODEL
  
  SELECT      COMPONENT EXTERNAL
  
  ****** STATUS OF NODES ******
  NUMBER OF SELECTED NODES=        16
  NUMBER OF DEFINED NODES=        208
  MAXIMUM NODE NUMBER=            208
  
  ****** STATUS OF ELEMENTS ******
  NUMBER OF SELECTED ELEMENTS=         0
  NUMBER OF DEFINED ELEMENTS=         27
  MAXIMUM ELEMENT NUMBER=            126
  
  SELECT      ALL ELEMENTS HAVING ANY NODE IN NODAL SET.
  
            9 ELEMENTS (OF         27 DEFINED) SELECTED FROM
         16 SELECTED NODES BY ESLN COMMAND.
  
  ****** STATUS OF NODES ******
  NUMBER OF SELECTED NODES=        16
  NUMBER OF DEFINED NODES=        208
  MAXIMUM NODE NUMBER=            208
  
  ****** STATUS OF ELEMENTS ******
  NUMBER OF SELECTED ELEMENTS=         9
  NUMBER OF DEFINED ELEMENTS=         27
  MAXIMUM ELEMENT NUMBER=            126
  
  ELEMENT TYPE SET TO       100
  
  GENERATE ELEMENTS ON SURFACE DEFINED BY SELECTED NODES
  TYPE=      100 REAL=        1 MATERIAL=        1 ESYS=    0
  
  NUMBER OF ELEMENTS GENERATED=          1
  
  ****** STATUS OF NODES ******
  NUMBER OF SELECTED NODES=        16
  NUMBER OF DEFINED NODES=        208
  MAXIMUM NODE NUMBER=            208
  
  ****** STATUS OF ELEMENTS ******
  NUMBER OF SELECTED ELEMENTS=        10
  NUMBER OF DEFINED ELEMENTS=         28
  MAXIMUM ELEMENT NUMBER=            127
  
  SELECT ALL ENTITIES OF TYPE= ALL AND BELOW
  *********************Ende surf152*********************
  
  Why are 45 elements selected via esel ?
  
  SELECT       FOR ITEM=ENAM COMPONENT=
  IN RANGE       152 TO        152 STEP          1
  
           45 ELEMENTS (OF         72 DEFINED) SELECTED BY ESEL COMMAND.
  
  There shouldn'be any surf152 elements because it's the first step!
  The output indicated that one surface element is created, I guess at the centre of the top surface. Because all external nodes of the element surface are necessary to create a surf152 element at the exterior element surface.
  After re-entering the /solu I try to select the in /prep7 created surf152 elements with this code:
  …
  nsel,none
  esel,none
  esel,s,type,,100
  esel,s,ename,,152
  esel,s,mat,,100
  cm,surf_test,elem
  
  allsel,all
  outres,all,all
  *enddo
  
  The solver output is this:
  
  NONE SELECT FOR ITEM=NODE COMPONENT=
  IN RANGE         1 TO        208 STEP          1
  
            0 NODES (OF        208 DEFINED) SELECTED BY NSEL COMMAND.
  
  NONE SELECT FOR ITEM=ELEM COMPONENT=
  IN RANGE         1 TO        126 STEP          1
  
            0 ELEMENTS (OF         72 DEFINED) SELECTED BY ESEL COMMAND.
  
  *** WARNING ***                         CP =       0.797   TIME= 11:00:37
  Entity 100 is undefined. The ESEL command is ignored.
  
  SELECT       FOR ITEM=ENAM COMPONENT=
  IN RANGE       152 TO        152 STEP          1
  
           45 ELEMENTS (OF         72 DEFINED) SELECTED BY ESEL COMMAND.
  
  SELECT       FOR ITEM=MAT COMPONENT=
  IN RANGE       100 TO        100 STEP          1
  
            0 ELEMENTS (OF         72 DEFINED) SELECTED BY ESEL COMMAND.
  
  DEFINITION OF COMPONENT = SURF_TEST ENTITY=ELEM
  
  SELECT ALL ENTITIES OF TYPE= ALL AND BELOW
  
  WRITE ALL ITEMS TO THE DATABASE WITH A FREQUENCY OF ALL
     FOR ALL APPLICABLE ENTITIES
  
  *ENDDO INDEX= I
  
  I don’t understand this, because one surf152 element is created in the /prep7, but in the /solu I can’t select it via esel.
  I also don't understand why 45 surf152 are selected prior in the /prep7 in the first step, there shouldn't be any of these
  
  With best regards
  John
- March 13, 2023 at 4:40 pm
  
  danielshaw
  Ansys Employee
  
  It is difficult to debug MAPDL scripting in Mechanical without the model and full access to the script? For example, it is not clear why you believe that there are no SURF154 in the 1st load step. Did you create the surf elements in 2nd load step? I recommend that you open a Service Request through the Customer Portal, so that you can provide the model to us.