Variations in the Value of Reynolds Number at the Transition from Streamline to Turbulent Flow

Abstract

THE flow of nitrogen through a porous copper disk has been investigated experimentally at mean pressures of 2–80 atm., and the flow of carbon dioxide through the same disk has been investigated up to mean pressures of 50 atm., at room temperature. The difference in pressure across the disk was never more than 0.6 atm. and was as small as 0.2 atm. in some experiments. As the mean pressure was increased from 2 atm. the flow through the disk remained streamline up to mean pressures of nitrogen of about 70 atm. and up to mean pressures of carbon dioxide of about 40 atm., the value of the pressure at which the flow departed from streamline flow being dependent on the pressure difference. Results showing the departure of the flow from streamline flow are given in Fig. 1A; some of the mean pressures are shown in Fig. 1 opposite the relevant points; but most pressures have been omitted so as not to confuse the diagram. The straight line represents streamline flow through the disk. Points lying off the straight line are usually attributed to the onset of turbulence; accepting this interpretation if R′_e be the value of the Reynolds number at which turbulence begins then it is apparent from Fig. 1 that (1) R′_e for nitrogen is different from that for carbon dioxide; (2) R′_e for carbon dioxide diminishes as the mean pressure increases.