flow of fluids

Question 0

what is laminar flow?

Answer 0

fluid moving steadily without turbulence

Question 1

How is flow represented

Answer 1

Q=flow; A=amount; T=time

Q=A/T

Question 2

what is the name of the waveform created as some of the flow drags on the walls of the tube?

Answer 2

parabolic waveform

Question 3

under conditions of laminar flow, flow is proportional to what?

Answer 3

flow is proportional to pressure…

Question 4

what is the formula for the ratio of pressure to flow (aka. Resistance)?

Answer 4

R= resistance; P= pressure; Q=flow

R=P/Q

Question 5

1. what is the Hagen-Poiseulle equation?

2. what does it explain?

Answer 5

1. Q=pie x change in pressure x radius to the 4th power/ 8x viscosity x length of tube
2. describes laminar flow thru a tube

Question 6

what is change of pressure in the Hagen Poiseuille equation?

Answer 6

driving pressure (inlet pressure minus outlet pressure)

Question 7

(based on the formula) if you decrease the radius of a tube by half, how much is the flow decreased by?

Answer 7

decreasing the radius by 1/2 decreases the flow by 1/16

Question 8

1. what 2 things is Q proportional to?

2. what 2 things is Q inversely proportional to?

Answer 8

1. Q (flow)is proportional to the change in P and
   - -Q is proportional to the radius to the 4th
2. Q is inversely proportional to the length (l)
   - –Q ins inversely proportional to viscosity (n)

Question 9

how would you calculate the difference between a #8 and #6 tube (1/4 decrease in size)?

Answer 9

1. calculate flow of a #8 tube (which is radius to the 4th):
   - —-8x8x8x8=4,096
2. calulate the flow of a #6 tube.
   - —-6x6x6x6=1,296
3. calculate the factor or % of original flow left by dividing the flow of #8 by #6 tubes (4096/1296=3.16)
4. multiply by 10% to get percentage of flow left (31.6%)
5. 100%- 31.6%=68.4% decrease

Question 10

1. with turbulent flow, Q is proportional to what (regarding pressure)? what does this mean?
2. Q is also proportional to what (regarding radius)? what does this mean?

Answer 10

1. with turbulent flow, Q is proportional to the square root of pressure (this means there is less increase in Q for any given pressure increase than is seen with laminar flow).
2. with turbulent flow, Q is also proportional to the radius squared. (this means radius has less effect with turbulent flow than with laminar).
3. with turbulent flow, Q is inversely proportional to length and density (flow is increased with shorter tube and turbulent flow decreases in more dense medium).

Question 11

1. what is Reynold’s number formula?
2. what does the reynold’s number mean?
3. what is the cutoff number for reynold’s number?

Answer 11

1. reynolds number=velocitypressurediameter / viscoxity
2. the onset of turbulent flow occurs with sharp increases in velocity of Q through a tube (i.e. at constrictions).
3. if reynolds number is greater than (>2000), turbulent flow is likely;
   if less than (<2000), laminar flow is likely

Question 12

1. what does turbulent flow cause (as far as breathing)?

2. what conditions (normal and pathologic) cause turbulent flow?

Answer 12

1. turbulence causes increased work of breathing

2. asthma, coughing, speaking, deep breathing

Question 13

what is a venturi?

Answer 13

a tube with a narrowing followed by progressive widening

Question 14

what is bernoulli’s principle?

Answer 14

pressure within a stream of gas flowing through a tube is the lowest at the narrowest point (can even be sub atmospheric)

Question 15

1. what determines viscosity?

2. what determines density?

Answer 15

1. how thick a liquid is (sugar water is thicker than tap water)
2. how heavy a fluid is per unit volume (salt water is denser (heavier) than tap water)