  As a necessary preliminary step toward geophysically significant
extrapolations, we study the scale effects in internal wave attractors in the
linear and nonlinear regimes. We use two geometrically similar experimental
set-ups, scaled to factor 3, and numerical simulations (a spectral element
method, based on the Nek5000 open solver) for a range of parameters that is
typically accessible in laboratory. In the linear regime, we recover the
classical viscous scaling for the beam width, which is not affected by
variations of the amplitude of the input perturbation. In the nonlinear regime,
we show that the scaling of the width-to-length ratio of the attractor branches
is intimately related with the energy cascade from large-scale energy input to
dissipation. We present results for the wavelength, amplitude and width of the
beam as a function of time and as a function of the amplitude of the forcing.
