Improved PML for the FDTD solution of wave-structure interaction problems

In a previous paper, an optimum perfectly matched layer has been designed for the finite-difference time-domain (FDTD) solution of wave-structure interaction problems. The present paper shows the results of subsequent investigations that were done with the intention of reducing the thickness of this optimum PML. Four improvements to the PML are presented. The resulting reductions of the thickness are discussed.