How to calculate n with its uncertainty in the equation Q= kL(h^n)?

  • #1
Joon
85
2
Homework Statement:
I was given a flow rate equation Q= kL(h^n), where k is a constant and L (width of rectangular weir) was set to 0.625 ft. A table of experimental Q values and corresponding h' and h values was provided, please refer to the picture attached. h (weir head) in the equation= h in the table. h= h' -0.3290 ft.

There are two variables in the equation, Q and h, and I need to determine the experimental value of n.

An example calculation was provided where the used equation was D=cE^n and I was told to use the same method as the one used in the example calculation. Please refer to the attached files 2-4 for the example calculation.
I get how to calculate the uncertainty of D, but I really have no idea how the uncertainty of E was calculated.
After calculating U(D) and U(E), a plot of ln (D) against ln (E) was drawn to calculate n (the gradient of the graph).

Could someone help me understand this?
Relevant Equations:
Q= kL(h^n) for the task

D=cE^n for the example calculation

Hook gauge reading, weir head- vernier scale
Flow rate Q reading- venturi flow meter
I am thinking of doing the same thing (summing up all the uncertainties that contribute to U(E) in the example) for the task, so summing up all the fractional uncertainties that contribute to U(Q). But the problem is unlike energy in the example, I'm not sure what's the contributors that lead to U(Q).
 

Attachments

  • Data given.png
    Data given.png
    5.5 KB · Views: 233
  • Example.png
    Example.png
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  • U(E) 1.png
    U(E) 1.png
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  • U(E) 2 and U(D).png
    U(E) 2 and U(D).png
    60.1 KB · Views: 297
Last edited:

Answers and Replies

  • #2
BvU
Science Advisor
Homework Helper
15,360
4,337
I must be missing something: in the example I don't see a calculation of ##n## at all, only a (remarkable coincident) result for ##g## ? :confused:
 
  • #3
Joon
85
2
The process is a bit complicated, I am uploading everything I have, please have a look.
I'm attaching the excel file as well where the example calculation was done.
 

Attachments

  • Excel file.xlsx
    37 KB · Views: 165
  • 1st.png
    1st.png
    111 KB · Views: 238
  • 2nd.png
    2nd.png
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  • 3rd.png
    3rd.png
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  • 4th.png
    4th.png
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  • #4
Joon
85
2
2 more files
 

Attachments

  • 5th.png
    5th.png
    104.4 KB · Views: 244
  • 6th.png
    6th.png
    67.6 KB · Views: 198

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