ANALYSIS OF THE ENTROPY IN FAST TIME DOMAIN SIMULATIONS OF REVERBERATION CHAMBERS

In this contribution, we investigate the entropy growth in a mode-stirred cavity simulated by the FDTD method. The adopted reverberation chamber is efficiently stirred by paddles and excited by a Gaussian pulse. It is observed that the entropy starts growing quadratically in time, then it increases linearly during the energy buildup, and it saturates after a few nanoseconds, when the onset of disordered fields occur. This allows for terminating the numerical simulations well before the Richardson time, as the asymptotic entropy is rapidly achieved. The analysis is based on the eigenvalues of the correlation matrix, calculated over a dense grid of spatial points, thus supporting the perspective of the reverberation chamber as a statistical multivariate process.