Discussion Forum

At the moment I do laminar flow simulations in 2D. I was wondering, if the shallow channel approximation is useful for me. The Navier-Stokes equation from laminar flow to laminar flow with shallow channel approximation differs by the summand "-12viscosity(kinematic)velocity vector/diameter^2". The diameter indicates the channel height. I didn't found any further documentations about this shallow channel approximation in the comsol documentations, blog etc. The additional term obviously takes the channel height into account, while the simple 2D laminar flow does not. But where does the term come from? What geometrical properties the geomery should be fullfilled to use the shallow channel approximation (aspect ratio or length scale µm or mm)? Thank you for your help!