.TAeZoSysPro.FluidDynamics.BasesClasses.MolecularDiffusion

Information

This components allows to model the mass flow rate induced by the gradient of concentration of species within a binary gas mixture. The mass flow rate of species derives from the Fick's equation.

The physical model under this module uses the following assumptions:

• the total concentration of the mixture is approximately constant

Where:

• m_flow j is the mass flow rate of the species 'j' [kg.m^-2.s^-1]
• ρ is the density of the mixture [kg.m^-3]
• Dij binary coefficient of diffusion from 'i' to 'j' [m².s^-1]
• cj mass fraction of the species 'j' [-]

The quantities contained in the equation are such that Dij = Dji (symmetry of the interaction between particles i and j) and ci + cj = 1 (by definition of the mass fraction). It is deduce that diffusion does not globally transport mass, it only distributes it differently:

Therefore an to avoid mass transport, the global density used in the equations above are computed at the middle of the diffusion length.

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