Flow through gel-walled tubes

The phenomenon discovered by J. Lahav, N. Eliezer, and A. Silberberg (Biorheology 10, 595, 1973) that flow through gel-coated tubes is subject to considerably increased drag was further examined. Data were taken over a much wider range of flow and it was shown that the functional dependence of the loss of throughput on the Reynolds number is similar to that in incipient turbulent flow through rigid tubes indicating a comparable mechanism. With gel-walled tubes, however, the effects are observable at much lower Reynolds numbers. The parameter α, the shear strain induced by the flow in the gel mantle, correlates with the throughput data obtained with all gel-coated systems over the entire range. The functional interdependence of all these parameters has been derived. The impression is gained that oscillations in the gel wall induce a turbulent boundary layer while core flow remains laminar. As Reynolds number increases the “boundary layer” encompasses the entire tube.