Scaling of impulsively started, incompressible, laminar round jets and pipe flows

Numerical solutions of the complete Navier-Stokes equations in the 70-500 Reynolds number range are used to deduce the scaling law of transient and steady, laminar, incompressible round jets, and the results obtained are compared with available experimental data. It is established that the axial length scale is equal to the product of the Reynolds number and the diameter of the orifice; the time scale is equal to the square of the orifice diameter divided by the kinematic viscosity. These scales are also found to apply to the entrance and fully developed regions of transient and steady pipe flows for Reynolds numbers greater than 10.