Liquid plug flow in straight and bifurcating tubes

A finite-length liquid plug may be present in an airway due to disease, airway closure, or by direct instillation for medical therapy. Air forced by ventilation propagates the plug through the airways, where it deposits fluid onto the airway walls. The plug may encounter single or bifurcating airways, all airway surface liquid, and other liquid plugs in nearby airways. In order to understand how these flow situations influence plug transport. benchtop experiments are performed for liquid plug flow in: Case (i) straight dry tribes, Case (ii) straight pre-wetted tubes, Case (iii) bifurcating city tribes, and Case (iv) bifurcating tribes with a liquid blockage in one daughter Data are obtained for the trailing film thickness and plug splitting ratio as a function of capillary number and plug volumes. For Case (i), the finite length plug in a dry tube has similar behavior to a semi-infinite plug. For Case (ii), the trailing film thickness is dependent upon the plug capillary, number (Ca) and not the precursor film thickness, although the shortening or lengthening of the liquid plug is influenced by the precursor film. For Case (iii), the plug splits evenly between the nvo daughters and the depositedfilin thickness depends oil the local phig Ca, exceptfor a small discrepancy that may be due to air entrance effect or from curvature of the tubes. For Case (iv), a plug passing from the parent to daughters will deliver more liquid to the unblocked daughter (nearly double, consistently) and then the plug will then travel at greater Ca in the unblocked daughter as the blocked. The floss, asymmetry, is enhanced for a larger blockage volume and diminished for a larger parent plug volume and parent-Ca.