Windmills WIPL-D EM Simulations
The WIPL-D implementation of MoM is an ideal candidate for RCS simulations of electrically large structures. A number of features leads to this: unique quad mesh applying higher order basis functions, CAD tool providing the optimum mesh, efficient implementation at CPU/GPU platforms and number of methods to reduce number of unknowns at EM insignificant model parts.
The code is pushed to the limits for the case of wind turbines. The main challenge represents the electrical height of the mils which is very large at frequencies of interest, and presence of resistive dielectric layers. The usual result required for the case of wind turbines is near field in the shadow zone.
The application note offers an unconventional combination of three simulation methods. The first method is WIPL-D 2D solver allowing simulation of infinite cylinders, both, coated or PEC, in seconds. This is a good approximation for modeling of either windmill mast or nacelle.
In the next step, the DDS solver is used as high frequency method for electrically large structures. The accuracy of the tool for the particular case is verified first by simulating PEC mast and comparing results with the default MoM full wave simulation. The result of interest is near field up to 50 km behind 50 m tall mast, at the height of 25 m. The iterative DDS method yields accurate solution after two iterations.
The final goal is simulation of entire wind turbine coated with single dielectric resistive layer. The simulation frequency is 3 GHz. Such a simulation is impractically large for MoM as in that case resulting million unknowns simulation lasts around 2 days on a workstation with 2 CPUs with 12 cores, plenty of RAM, four inexpensive Nvidia GTX cards and 5 fast SSD discs. On the other hand, using the same machine, the DDS requires only as many cores as possible. The same applies to RAM. The simulation time is now a couple of hours for PEC windmill and 1 2 days for the coated case (nearly 3 million unknowns).
For full version of the document, please check the following pdf.