The Reynolds number is a dimensionless quantity indicator for the ratio of the forces of inertia to the forces of viscosity or friction in flowing Newtonian liquids. It depends on the flow velocity v, the
line cross section d i related to a circular area and the kinematic viscosity v:
The critical Reynolds number states the point of transition from laminarto turbulent flow, which has a value of Re = 2,300 under ideal conditions with a smooth pipe. In the case of other, more complex cross sections, part of the transition takes place at significantly smaller Reynolds numbers (Table R 1).
Round smooth pipes 2,200 to 2,300 concentric smooth gaps 1,100 to 1,200 eccentric smooth gaps 1,000 to 1,050 concentric gap with recesses 700 eccentric gap with recesses 400 rotary vanes (spigots) 550 to 750 valve ports of spools 250 to 275 valves with flat or conical seat 25 to 100
Figure Table R 1: Reynolds numbers in the case of different flow cross sections
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