Opera includes an easy-to-use 3D Modeller, allowing models to be created or imported -in a wide variety of standard CAD formats; Scripting in the Modeller makes it a simple matter to automate the build of families of products. Once built and prepared for simulation (in the Modeller), Opera offers a range of FE solvers, enabling static, harmonic and transient EM – and incorporating linear and rotational motion for machine design. In recent times, advances in computer hardware and software capability have allowed Opera to successfully solve many challenging multi-physics problems. Coupling of EM simulations to thermal and stress simulations in Opera has now been automated with the introduction of a multi-physics interface and database, in which several simulations are set up in a single model, and the appropriate results data are passed automatically from one simulation to the next.
Opera can couple FE models to its circuit model and perform cosimulation; this allows models to be excited by a circuit comprising voltage and current sources, resistors, capacitors, inductors, switches and diodes. Opera has a built in Optimizer – a software tool which can assist users in achieving the “best” designs. The Post-Processor includes an extensive set of data extraction tools – with flexibility and capability enhanced by an in-built scripting facility – the same facility that is available in the Modeller for model creation and preparation. The recent integration of Python scripting into Opera gives the user access to an even wider range of data manipulation and processing features. There are several application specific environments developed: Machines Environment, Transformers and Quench Multiphysics.
Opera includes both thermal and stress solvers, in addition to its range of EM solvers. In Opera, we can chain any number of stages of analysis – all based on a single model. This model includes all set-up options, material properties, boundary conditions, etc, as appropriate, for each type of simulation: EM, thermal and stress.
As we chain several simulations into one model, we create a single database shared by all simulations. Results of thermal and structural analyses are of great importance for designing real systems and investigating effects essential for operation of EM devices (overheating, outgassing, vibrations, etc.).
Coupling different analyses can be performed using either Multiphysics interface from Opera-3d Modeller or look-up tables. Both methods have their own advantages and disadvantages.
Let us consider a very simple example of a Static Thermal analysis coupled with a Static Stress.
Given the properties of the emitters, primary and secondary, the Charged Particle analysis predicts trajectories of the particles, beam current density and power density. By integrating power densities on patches immediately before the mask and after the mask we can get the power absorbed by the mask, i.e. 535 W.
The results show that the maximum temperature on a surface of the mask is 231OC and the highest temperature in the cooling channels is 206OC. We can conclude therefore that cooling of the copper block is not adequate for the amount of heat absorbed by the mask.
In the 2nd example we demonstrate a model of a heating bath where a conducting material is heated by Eddy currents induced by a magnetic field. The multi-physics model has two parts: Harmonic EM and a static Thermal analysis.
Induction welding is a commonly used industrial process for joining materials together. In this example we describe how Opera FEA software can be used to simulate the induction welding process by considering an example of joining together two thin plates of CFRP (Carbon Fibre Reinforced Polymers).
The model includes Harmonic Electromagnetic and Transient Thermal analyses and uses tables to exchange data between the two solvers. In this model, we assume that there is no heat barrier at the interface between the CFRP plates. In fact, Opera could include a thermal contact conductance, if a suitable value was known. To take into account some heat dissipation from the external surfaces of the plates into surrounding air we apply a small heat transfer coefficient (of 20 W/(m2 K)) to the interface between the air and the sheets.
As motion of the coil occurs on a much slower time-scale than the variation of the field at 1 MHz, it does not have any significant effect on the electromagnetic analysis. Consequently, it is only necessary to move the power density distribution when the coil moves to a new position at each thermal time-step. This power density distribution is either a newly calculated one or the one calculated at a previous position, if the maximum temperature changed only slightly (by less than 25oC) and hence the electrical conductivity of the CFRP has not changed considerably.
The Figure demonstrates temperature ‘trace’ of the moving coil on the surface of the CFRP when the coil moves along the surface of the sheets at different speeds.
The Opera-3d Quench module uses a finite element method to simulate the transient thermal and transient electromagnetic behaviour of superconducting coils and magnets.
Coupled Quench has the necessary communication to pass data between electromagnetic and thermal simulations Temperature: thermal . EM Magnetic and electric field: EM => thermal
Variation of current in the coils is shown in this slide. The arrows correspond to t = 0.1 s, 0.5 s and 1 s.