Lee Jin W, Kang Min Y, Yang Hoe J, Lee Eugene
Department of Mechanical Engineering also Systems Bio-Dynamics Research Center, Pohang University of Science and Technology, Hyoja 31, Pohang, Kyungbuk 790-784, South Korea.
Med Biol Eng Comput. 2007 Nov;45(11):1071-8. doi: 10.1007/s11517-007-0232-8. Epub 2007 Jul 25.
It is shown in this paper that the nearly constant length-to-diameter ratio observed with conducting airways of human bronchial tree can be explained based on the fluid dynamic optimality principle. In any branched tube there are two pressure loss mechanisms, one for wall friction in the tube section and the other for flow division in the branching section, and there exists an optimal length-to-diameter ratio which minimizes the total pressure loss for a branched tube in laminar flow condition. The optimal length-to-diameter ratio predicted by the pressure loss minimization shows an excellent agreement with the length-to-diameter ratios found in the human conducting airways.
