Fractional flow
= Fractional flow
{title2=$F_w=\lambda_w/(\lambda_w+\lambda_n)$}
The fraction of total advective <Darcy flux> carried by one phase when capillary and gravity corrections are omitted. For two phases it is $\lambda_w/(\lambda_w+\lambda_n)$. This quantity lies between zero and one for nonnegative <phase mobilities>. Its nonlinear dependence on <fluid saturation> determines <characteristic speeds> and shocks in the <Buckley-Leverett equation>.