The differential energy equation for incompressible two-dimensional flow through a Darcy-type porous medium is approximately Where is

The differential energy equation for incompressible two-dimensional flow through a “Darcy-type” porous medium is approximately
Where σ is the permeability of the porous medium, all other symbols have their usual meanings.
(a) What are the appropriate dimensions for σ?
(b) Non-dimensionalize this equation, using (L, U, ρ, To) as scaling constants, and discuss any dimensionless parameters which arise.