Figure 1 – NSTX Upper Umbrella Assembly Upgrade Design: Version 4

Figure 2 – Single Segment 3-Strap Assembly Solid Model: Version 4

Figure 3 – ANSYS Multiphysics Analysis Block Diagram

Figure 4 – Single Segment 3-Strap Assembly FEA Model: Mesh

Figure 5 – Single Segment 3-Strap Assembly Electric Model Results: Voltage

Fig. 6 – Single Segment 3-Strap Assembly Electric Model Results: Current Density

Figure 7 – Single Segment 3-Strap Assembly Electric Model Results: Joule Heat

Fig. 8 – Single Segment 3-Strap Assembly Thermal Model Results: Temperature

Study: Determine Current Best-Practice to Perform Magnetostatic Analysis in ANSYS 12.0 WorkBench

• New SOLID236/237 magnetic analysis elements – Have both Magnetic Vector Potential (MVP) and Line Edge method capability.

Replaces SOLID97 and SOLID117.– Compatible with WB generated Electric, Thermal, and Static Structural analyses

meshes.

• No 3D MVP or Line Edge contact elements– Requires conformal mesh with shared nodes across the joints, which makes

modeling assemblies including frictional and pressure-dependent electric and thermal contact impossible, or

– Non-conformal/ dissimilar mesh, with duplicate nodes across the joint. Magnetic coupling using CPINTF command requires nearly-matched meshing, which is difficult to achieve in a large assembly.

• Above problems are greatly reduced if modeling the air enclosure, and modeling the magnetic coupling across the joints, are not necessary

– May be valid for materials with a relative magnetic permeablity = 1.– Goal: Prove with a comparison study.

Outer-most Lamination Arch Segment with Air Enclosure: Solid Model

Merged Volumes

Outer-most Lamination Arch Segment with Air Enclosure: Mesh

Conformal Mesh:

Nodes shared at Interface(perfect magnetic coupling)

Arch Segment w/ Air Magnetostatic Model Results: Current Density (A/m^2)

Arch Segment w/ Air Magnetostatic Model Results: Joule Heat

SOLID236:LINE EDGE METHOD

Arch Segment w/ Air Magnetostatic Model Results: Magnetic Flux (Metal +Air)

Arch Segment w/ Air Magnetostatic Model Results: Magnetic Flux (Metal Only)

Arch Segment w/ Air Magnetostatic Model Results: Current Density

Arch Segment w/ Air Magnetostatic Model Results: Lorentz Forces (N)

Arch Segment w/ Air Magnetostatic Model Results: Magnetic Flux (Metal Only)

Arch Segment w/ Air Magnetostatic Model Results: Lorentz Forces (N)

Arch Segment w/ Air Static Structural Model Results: von Mises Stress (Pa)

SOLID186

Stress and reaction force results closely agree with hand-calculated values.

SOLID236LINE EDGE METHOD

Arch Segment _No Air - Magnetostatic Model Results: Magnetic Flux (Tesla)

Arch Segment _No Air - Magnetostatic Model Results: Current Density (A/m^2)

Arch Segment _No Air - Magnetostatic Model Results: Lorentz forces (N)

Arch Segment _No Air - Magnetostatic Model Results: Magnetic Flux (Tesla)

Arch Segment _No Air - Magnetostatic Model Results: Lorentz Forces (N)

SOLID186

Stress and reaction force results closely agree with hand-calculated values.

Arch Segment _ No Air - Static Structural Model Results: von Mises Stress (Pa)

Conclusion

• SOLID117 results are not valid, but SOLID236 results using line edge method agree with hand-calculated classic solution values.

• No difference between results with air enclosure modeled and without. Note: Modeling without air enclosure is valid only for cases where all materials have a relative magnetic permeability = 1.