Properties of thermocapillary fluids and symmetrization of motion equations

Henri Gouin (1)

1 IUSTI - Institut universitaire des systèmes thermiques industriels

The equations of fluid motions are considered in the case of internal energy depending on mass density, volume entropy and their spatial derivatives. The model corresponds to domains with large density gradients in which the temperature is not necessary uniform. In this new general representation writes in symmetric form with respect to the mass and entropy densities. For conservative motions of perfect thermocapillary fluids, Kelvin's circulation theorems are always valid. Dissipative cases are also considered; we obtain the balance of energy and we prove that equations are compatible with the second law of thermodynamics. The internal energy form allows to obtain a Legendre transformation inducing a quasi-linear system of conservation laws which can be written in a divergence form and the stability near equilibrium positions can be deduced. The result extends classical hyperbolicity theory for governing-equations' systems in hydrodynamics, but symmetric matrices are replaced by Hermitian matrices.

Mots clés: Thermocapillarity; second gradient models; fluid interfaces; hyperbolicity

Domaines: Matière Molle [cond-mat.soft]; Mécanique des fluides [physics.class-ph]; Chimie théorique et/ou physique

Henri Gouin. Properties of thermocapillary fluids and symmetrization of motion equations. International Journal of Non-Linear Mechanics, 2016, 85, pp.152 - 160. ⟨10.1016/j.ijnonlinmec.2016.06.003⟩. ⟨hal-01541196⟩