1. Resistance in Fluid Systems
Mr. Andracke
Principles of Technology

2. Viscosity Fdrag =  x Av/ y
Viscosity has the units of (pressure) (time).
The SI units for viscosity are Pa x s
Fdrag =  x Av/ y

3. Stokes’ Law
Irishmen George Stokes used viscosity and the equations of fluid flow to predict the drag force on a sphere moving through a fluid.
Stokes’ Law applies to objects moving at low enough speeds that the flow of fluid is streamlined or laminar.

4. Stokes’ Law Fdrag = 6rv 6 =Constant for sphere R = Radius of object
V = Speed of object
 = Fluids Viscosity

5. Stokes’ Law
Fdrag = 6rv
Example:

6. Poiseuille’s Law
Poiseuille was a physician, who experimented with flowing water, and learned that the rate at which fluid flows through a tube increases proportionately to the pressure applied the fourth power of the radius of the tube.
Poiseuille’s Law gives the volume flow rate of a fluid flowing through a tube or pipe.

7. 3 Factors of Resistance
In fluid flow resistance decreases the flow rate though a pipe. Poiseuille’s Law shows how this resistance depends on three factors:
Dependence on Radius
Dependence on Length
Dependence on Viscosity

8. Dependence on Radius
The larger the radius of a pipe, the greater volume of fluid per second
Fluid resistance decreases as pipe radius and cross-sectional area increase.

9. Dependence on Length Longer pipes have higher fluid resistance
Volume flow rate is inversely proportional to length

10. Dependence on Viscosity
Abrupt changes in the direction of fluid flow can cause turbulence and increase resistance
Fluid resistance increases as viscosity increases.

11. Poiseuille’s Law V = -  r4 8 L R = Radius of Pipe or Tube
 = P2 – P1
= Viscosity
L = Length of Pipe or Tube

12. Poiseuille’s Law
V = -  r4 
8 L
Example:

13. Poiseuille’s Law Help with Poiseuille's Law

14. Complete the Math Lab Activity & Receive Handout for Tomorrows Lesson
Any Questions??
Complete the Math Lab Activity
&
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