Fluid dynamics in airway bifurcations: II. Secondary currents

As the second component of a systematic investigation on flows in bifurcati ons reported in this journal, this work focused on secondary currents. The first article addressed primary flows and the third discusses localized con ditions ( both in this issue). Secondary flow patterns were studied in two lung bifurcation models ( Schreck, 1972) using FIDAP with the Cray T90 supe rcomputer. The currents were examined at different prescribed distances dis tal to the carina. Effects of inlet conditions, Reynolds numbers, and diame ter ratios and orientations of airways were addressed. The secondary curren ts caused by the presence of the carina and inclination of the daughter tub es exhibited symmetric, multivortex patterns. The intensities of the second ary currents became stronger for larger Reynolds numbers and larger angles of bifurcation.