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hydro lab 2 questions

# hydro lab 2 questions - which are all within ±0.003 of...

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Questions: 1) Using Equation 7, I found Cd to be 0.687 for the sharp edge and 1 for the re- entrant. By using equation 6, the values I found for Cd with the sharp edge were all ±0.001 from 0.687 except for one trial which was 0.027 off and can be considered a miss-trial. With the re-entrant, the values were all ±0.003 from 0.687. 2) Assuming a plan area of 0.0412 m^2, the greatest velocity of approach in the upper reach is 0.128 m/s. In comparison with a velocity of 8.5 m/s at the orifice opening, the velocity in the upper reaches in negligible. It is a full power of ten higher and would therefore not be affected by the upper reach velocity. 3) I do not observe the Reynolds number having any influence on my measured values of Cd for either orifice type. All of my Reynolds numbers are within ±10,000 of each other, but they do not appear to be affecting my values of Cd,
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Unformatted text preview: which are all within ±0.003 of each other. 4) The discharge coefficient might be dependent on the discharge at low water head because of equation 6. Since you are taking the square root of Ho, when it is a lower number it will impact the value of Cd even less. Because of this, the discharge, Qa, will impact Cd much more. 5) The coefficient values obtained for the sharp-edged are about 0.313 lower than the values for the re-entrant. This is due to the fact that in equation 7, Cd = CvCc. For the re-entrant, Cv = Cc while in the sharp edged, Cv is greater than Cc. 6) According to equation 6, there is no possible way to have flow when Ho = 0. The only way I could account for it is if there was still some liquid dripping off the orifice and was not being counted as Ho, but still counted as Qa....
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