关键词: laminar flow, entrance region, velocity distribution, pressure loss, entrance length, solid-fluid interaction, phase-density equation, Eulerian method, diffuse interface model, neisen equation of state (EOS), MieGrü

Abstract: For solid-fluid interaction, one of the phase-density equations in diffuse interface models is degenerated to a "0=0" equation when the volume fraction of a certain phase takes the value of zero or unity. This is because the conservative variables in phasedensity equations include volume fractions. The degeneracy can be avoided by adding an artificial quantity of another material into the pure phase. However, nonphysical waves, such as shear waves in fluids, are introduced by the artificial treatment. In this paper, a transport diffuse interface model, which is able to treat zero/unity volume fractions, is presented for solid-fluid interaction. In the proposed model, a new formulation for phase densities is derived, which is unrelated to volume fractions. Consequently, the new model is able to handle zero/unity volume fractions, and nonphysical waves caused by artificial volume fractions are prevented. One-dimensional and two-dimensional numerical tests demonstrate that more accurate results can be obtained by the proposed model.

Key words: laminar flow, entrance region, velocity distribution, pressure loss, entrance length, phase-density equation, Eulerian method, diffuse interface model, solid-fluid interaction, MieGrüneisen equation of state (EOS)