Lawrence Livermore National Laboratory

A simulation of a physical experiment uses large magnetic fields to compress a thin wall aluminum tube. The geometry consists of a robust steel outer tube and a 0.030-in. inner aluminum tube; the tubes are connected together at one end and connected to a header at the other end. In the physical experiment this device is connected, via 12 cables, to three 10-kV capacitor banks which are discharged simultaneously. In the ALE3D simulation, the capacitor bank and associated cables are modeled by an RLC circuit which is coupled to the Magneto Hydrodynamics (MHD) partial differential equations (PDEs). A large magnetic field exists in the space between the tubes, resulting in a large 'magnetic pressure' that will compress the inner tube.

Ale3D Magneto-Hydrodynamics

The simulation exercises the coupling of magnetic fields with explicit hydrodynamics. The thin aluminum tube is constrained to be Lagrangian, but in the air region mesh relaxation is allowed. Since the temperature rise is small, heat transfer is ignored. In the physical experiment both strain gauges and photonic doppler velocimeters were used to measure the deformation, and ALE3D results correlated quite well with this data.