= Equilibrium settling-diffusion profile
{title2=$\phi(z)=\phi_1(z/z_1)^{-W_s/K}$}
For downward <settling velocity> magnitude $W_s>0$ and <eddy diffusivity> $\kappa_T=Kz$, the total upward particle flux is $J=-W_s\phi-Kz\phi_z$. A stationary profile tending to zero at infinity has $J=0$, giving the displayed power law. The exponent compares settling with turbulent mixing. It describes a region above the bed; entrainment from the bed and viscous near-wall effects determine the reference concentration separately.
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