4.1. Basic principles
4.1.2. Flow

Flow

Keypoints

For laminar flow

For turbulent flow

Laminar flow

Principle

Flow calculation

For pure laminar flow,
--> Pressure (cmH2O) = Flow (L/sec) x Resistance

where

Hagen-Poiseuille equation

Laminar flow = Pressure x r4(pi)/8nl

Turbulent flow

Principle

Reynold's number (Re)

Formula

Re = DV x (d/n)

Significance

Thus,

Additional notes

Conductance

Conductance = 1/resistance
* Unit for conductance = L.cmH2O-1.sec-1

Entrance length

Entrance length - the distance required for laminar flow to be established
= 0.03 x diameter x Re

Viscosity

Viscosity
= ratio of shear stress to shear rate of the fluid

Unit for viscosity
--> dynes/cm2

Keywords:  Conductance ; Hagen-Poiseuille equation ; Laminar flow ; Reynold's number ; Turbulent flow
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Created20050527
Updated20050604
Reviewed20050527


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