Transitional (Tracheobronchial or Mixed) Flow

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Mixture of laminar and turbulent

At the same volumetric flow rate (volume of flow / amount of time) linear flow velocity is lower in small airways because of greater cross-sectional area.

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FIGURE 6-23 Fluid velocity, at a constant flow, varies inversely with the cross-sectional area of the tube. (Modified from Nave CR, Nave BC: Physics for the health sciences, ed 3, Philadelphia, 1985, WB Saunders.)

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Velocity of a fluid moving through a tube at a constant flow varies inversely with the available cross-sectional area

 

Exhalation- laminar pattern in bronchioles changes to turbulent in large airways

Inspiration – reverse occurs - turbulence in large airways changes to laminar in bronchioles

flow patterns in tb tree.jpg