  Similar to pure fluids, physical properties of a binary fluid mixture also
exhibit singularities close to its critical point, especially when it is
dilute. The numerical and theoretical results presented in this paper identify
that the piston effect, a rapid energy transfer phenomenon, can be induced by
boundary mass transfer in a confined near-critical binary fluid mixture. Due to
the Dufour effect, both the concentration and temperature variations are
responsible for the strong expansion of the boundary layer, which provokes an
acoustic wave propagating in the fluid, leading to a gradual increase of the
temperature, pressure and density. The detailed analysis implies that such a
mixed piston effect can be approximated as a direct superposition of their
respective effects in the perspective of energy transformation.
