An incompressible Newtonian fluid flows in a pipe of diameter D₁ at volumetric flow rate Q. Fluid with same properties flows in another pipe of diameter D₂ = D₁/2 at the same flow rate Q. The transition length required for achieving fully-developed flow is l₁ for the tube of diameter D₁, while it is l₂ for the tube of diameter D₂. Assuming steady laminar flow in both cases, the ratio l₁/l₂ is