General Information

1
Lab 2 - Flow Calculations

• General Information
• Worksheet and Spreadsheets due Thursday 12.00
  PM
• Lab Reports due Tuesday by 4.00 pm

• Objectives
• To measure flow rates
• To estimate uncertainty in measuring flow rates
• To determine how to make accurate flow rate
  measurements

2

• Theory
• Relationship between volume, time and flow rate

.(1)

• Uncertainty
• Time
• Ensure stopwatch is accurate to within 1
  assuming the quartz
• watch to be correct
• Estimate uncertainty by comparing the stopwatch
  with the lab clock

..........(2)
3

• Volume
• Estimate the least count (?) of the site gage
• Calculate uncertainty of site gage

.(3)

• Minimize other sources of uncertainty
• Human
• Same person will be taking the time reading for
  the rest of the semester
• Equipment same hydraulic bench will be used for
  the rest of the semester

4
Analysis

1. Calculate and plot the flow rates
2. Estimate the uncertainties in your basic
   measurements
3. Estimate the uncertainty in Q due to
   Uncertainties in V and T
4. Explore the uncertainty in Q that is possible
   for different measurement situations
5. Determine a method for measuring flow accurately
   in future experiments

5

• For 1 , 2 3 Tabulate and plot your readings

Volume 1I Volume 1I Volume 1I Volume 5I Volume 5I Volume 5I
Replicate t(s) Q(l/s) dQ/Q t(s) Q(l/s) dQ/Q
1
2

n
Q(avg) .

Where ,
and
6
Flow Rate vs Site Gage Reading
Figure 1. Replicate Flow Rate
7
For 4 5, you have to determine for what volume
will your uncertainty be less than 5 for maximum
flow rate (we will assume values with
uncertainty less than 5 are considered accurate)
Volume (L) Volume (L) Volume (L) Volume (L) Volume (L) Volume (L) Volume (L) Volume (L)
Q(l/s) 1 2 3 4 n
Q(l/s) 0.1
Q(l/s) 0.2
Q(l/s) 0.3
Q(l/s) 0.4
Q(l/s) 0.5
Q(l/s) Q (average From table 1) dQ/Q
8
Definition

• You can do this by extrapolating the uncertainty
  in Q

i, j is the row and column respectively

• Least count --- the smallest change in volume
  that you can reliably identify using the site
  gage