# Molar or mass averaged velocity in Darcy's law

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 May 22, 2020, 06:57 Molar or mass averaged velocity in Darcy's law #1 New Member   Daniel Join Date: Jun 2019 Posts: 4 Rep Power: 5 Hello there, can anyone help me to figure out, which type of velocity is used in Darcys Law. In literature some authors understand the Darcy-Velocity as a molar averaged velocity and some understand it as a mass averaged velocity. (The most of them use the mass averaged velocity but I wanna use the molar averaged velocity if possible because there are some advantages in my system.) In the original fomulation of Henry Darcy there shouldn't be a difference between both velocities because he observed a one-component system (flow of pure water). In a multicomponent system there could theoretically be a discrepancy because molar and mass averaged velocities are no longer the same. So based on the orignal Darcys law it should be possible to calculate either the molar or the mass averaged velocity from the pressure gradient. Is this thesis correct or does the derivation of Darcys law from Navier-Stokes Equations come to another result? Best regards Daniel

 Tags average velocity, darcy, darcy's law, navier stokes