Question:
We have used the "Paint" option and placed thermal SHELL131 elements over SOLID70 elements to act as a thin insulator coating with a 1-layer thickness. It is desired to use SURF152 surface effect elements on the exposed outside face of the SHELL131 elements. After ESURF meshing the SURF152 elements on the same nodes as were used for the SHELL131 elements, we find that convective loads on the SURF152 elements are acting on the face of the underlying solid element, not the exposed face of the SHELL131 element. Can you tell me what is going on?
Answer:
The problem here is the identification of the degree of freedom. The degree of freedom for the SURF152 is TEMP; the degree of freedom that the user is attempting to connect to is TTOP.
The SHELL131 element has 32 degrees of freedom, all of them temperature. To differentiate them, they were given names like T1, T2,...,TTOP and TBOT. When you use the PAINT option for the SHELL 131, ANSYS changes the degree of freedom from TBOT to TEMP so that the degree of freedom matches the solid element that the SHELL 131 is painted onto. When the user adds the SURF152s with the TEMP degree of freedom, those elements are effectively attached to the bottom of the SHELL131 where the degree of freedom is TEMP. The element itself doesn't know anything about position in space other than through the nodes.
The workaround for this problem is somewhat involved. It will be necessary to create a second area with new lines and keypoints and to mesh that second area with SURF 152 elements with new node number and element numbers. It will then be necessary to connect the SURF152 nodes to the SHELL131 nodes. Constraint equations may be the only answer here since most other coupling options (elements like LINK33 or CP command) have only the TEMP degree of freedom.The constraint equation would look like
CE,NEXT,0,node1,TEMP,1,node2,TTOP,-1
It will likely be convenient to create the mesh of the SOLID70 areas fi
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Question: We have used the "Paint" option and placed thermal SHELL131 elements over SOLID70 elements to act as a thin insulator coating with a 1-layer thickness. It is desired to use SURF152 surface effect elements on the exposed outside face of the SHELL131 elements. After ESURF meshing the SURF152 elements on the same nodes as were used for the SHELL131 elements, we find that convective loads on the SURF152 elements are acting on the face of the underlying solid element, not the exposed face of the SHELL131 element. Can you tell me what is going on? Answer: The problem here is the identification of the degree of freedom. The degree of freedom for the SURF152 is TEMP; the degree of freedom that the user is attempting to connect to is TTOP. The SHELL131 element has 32 degrees of freedom, all of them temperature. To differentiate them, they were given names like T1, T2,...,TTOP and TBOT. When you use the PAINT option for the SHELL 131, ANSYS changes the degree of freedom from TBOT to TEMP so that the degree of freedom matches the solid element that the SHELL 131 is painted onto. When the user adds the SURF152s with the TEMP degree of freedom, those elements are effectively attached to the bottom of the SHELL131 where the degree of freedom is TEMP. The element itself doesn't know anything about position in space other than through the nodes. The workaround for this problem is somewhat involved. It will be necessary to create a second area with new lines and keypoints and to mesh that second area with SURF 152 elements with new node number and element numbers. It will then be necessary to connect the SURF152 nodes to the SHELL131 nodes. Constraint equations may be the only answer here since most other coupling options (elements like LINK33 or CP command) have only the TEMP degree of freedom.The constraint equation would look like CE,NEXT,0,node1,TEMP,1,node2,TTOP,-1 It will likely be convenient to create the mesh of the SOLID70 areas first, followed by the mesh of the offset SURF152 areas next to have a constant offset for the node numbers that would permit the creation of the constraint equations with a *DO loop. |
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