Multiphysics
In a multiphysics system, two or more physical processes occur and interact in the same configuration. For instance, an electromagnetic field may lead to heat fluctuations in a structure, which may in turn lead to conductivity variations and shape deformations that affect the electromagnetic field. Multiphysics computational modeling is very challenging, since it involves time-varying media and often nonlinear interactions over a wide range of time scales. In addition to using commercial tools with (some) multiphysics functionality, we are developing time-domain computational techniques that are capable of handling specific and more generic multiphysics problems.
The finite-difference time-domain (FDTD) method is the workhorse of the computational electromagnetics toolbox. Discrete space-time Green's functions on a 3D simple cubic lattice can be used to formulate lattice Green's function (LGF) diakoptics, which is a 3D FDTD domain decomposition method [1]. In the EMPMC Lab, we have proposed a fast, no-neighbours, recurrence scheme for the discrete space-time LGFs. The figure illustrates a scalar LGF at the lattice point (1234,2345,3456) due to an impulsive point source at the origin. A 2D FDTD model of the Maxwell-Bloch pseudospin equations has been employed to study the short-pulse coherent dynamics in nonlinear optical waveguides and passive semiconductor microresonators [3]. FDTD domain decomposition could be used to render such simulations more efficient.
The marching-on-in-time contrast current density volume integral equation method developed in the EMPMC Lab, is a more flexible time-domain computational electromagnetics tool [4], that for certain multiphysics problems could be much more efficient.
An electromagnetic wave incident on a lossy copper via in a printed circuit board would heat up that via over time. A two-tone incident signal (see figure) causes periodicity in the heating that in turns leads to the generation of higher-order harmonics. This multiphysics effect is referred to as electrothermal passive intermodulation (ET-PIM), and can be modeled efficiently using a non-linear mixed time-frequency operator. An 5G/6G base-station antenna array produces a lot of heat, which, if not properly managed, will compromise the electromagnetic performance of the array. We are currently investigating heat-sink antenna-array heat management strategies.
[1] D. van den Hof, B. P. de Hon, 2022,
[2] B. P. de Hon, S.J. Floris and J.M. Arnold, 2018,
[3] G. Slavcheva, J. M. Arnold and R. W. Ziolkowski, 2003, .
[4] P.W.N. van Diepen, M.C. van Beurden, R.J. Dilz,