This thesis experimentally investigates non-equilibrium thermodynamics, wave propagation, and wave scattering in a thin elastic plate of dimensions 2 m × 1 m × 0.5 mm through three complementary studies.
The first part treats the vibrating plate as a non-equilibrium thermostat and compares two definitions of its characteristic energy. The first definition was derived from the fluctuation theorem applied to work exchange with an external probe and the second from the spectral analysis of velocity fluctuations. Both definitions differ quantitatively but converge qualitatively in defining the characteristic energy of a dissipative steady-state system.
The second part examines the emergence of large-amplitude, extreme wave events under harmonic forcing at selected frequencies. Laser Doppler vibrometers are used to perform point measurements of velocity and displacement. The detected extreme events are statistically characterized. These studies reveal how extreme fluctuations arise and show a correlation to the fundamental flexural mode of the plate.
The third part investigates the scattering of waves by localized mass defects placed on the plate. The investigations are conducted using a non-contact, two-dimensional measurement technique, Fourier Transform Profilometry. These measurements provide spatio-temporal visualizations of the velocity field and identifies regions of modified energy distribution due to the defect.
Together, these investigations offer new experimental perspectives on energy transfer, fluctuations, and wave dynamics in a macroscopic system driven far from equilibrium.