Laminar flow generally happens when dealing with low Reynolds Numbers in pipes. This could be due to low velocities, large diameters or high viscosities. Laminar flow can be modeled as a series of liquid cylinders in the pipe, where the innermost parts flow the fastest, and the cylinder touching the pipe isn't moving at all.
Shear stress in laminar flow is independent of the density - ρ, and the shear stress depends almost only on the viscosity - μ.
Tags: Equations for Flow