Fluid flow in tubes

Fluid flow in tubes

1. Laminar

2. turbulent

   • Heart murmur
     • can be heard with a stehoscope

3. three factors determine resistance

   • Vessel diameter
   • Vessel length
   • Viscosity of the blood

4. volumetric flow determined by three factors

   • pressure difference
   • Radius
   • Blood viscosity

5. Poiseullie's Law

   • states resistance to flow is a function of physical properties
   • Newtonian fluid, therefore viscosity is constant
   • Radius = power of four
     • important in determening resistance
   • Assumptions
     • Newtonian fluid
     • Laminar flow
     • No slip
     • steady flow
     • cylindrical shape
     • Rigid wall

6. Atherosclerosis

   • deposition of mineral deposits in blood flow
   • reduction in vessel size= greater P drop per length

7. Arteriosclerosis

   • General term for degenerative changes in arteries making them less elastic

8. Poiseuille or Bernoulli?

   • Large vessels
     • Poiseuille
   • small vessel, shear = low
     • non-Newtonian
       • Bernoulli's (constriction/dilation of a vessel also)

9. Blood pressure

   • required to transport blood
   • P drop due to viscosity
   • P drop as 1/R^4
     • consequences
       • capillaries
         • slow flow, high area=exchange of material
         • most heart energy = pushing blood through capillaries
         • obesity = large capillary area = heart work harder.
           • higher blood pressure
             • Hypertension
   • Arteries smaller away from heart
   • Highest P = Aorta, 11-18 kPa
     • approx 0 mmHg at termination of venae cava- right atrium