  A phenomenological two-fluid model of the (time-reversible)
spectrally-truncated 3D Euler equation is proposed. The thermalized small
scales are first shown to be quasi-normal. The effective viscosity and thermal
diffusion are then determined, using EDQNM closure and Monte-Carlo numerical
computations. Finally, the model is validated by comparing its dynamics with
that of the original truncated Euler equation.
