Fluid mechanics work

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Prelab-3-2018.pdf

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KNE351- Fluid Mechanics 1

Prelab Exercise 3

The critical velocity Vc over a weir may be expressed in terms of critical depth by c cV gy= 1 Apply the Steady Flow Energy Equation between an upstream section and a section on the weir crest

where the flow depth is critical to derive Equation [1], which describes volumetric flow rate Q in terms of channel width b, upstream weir head H, and upstream velocity V1 as shown above. Show all steps and clearly state all assumptions. You may assume negligible friction

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12 3 2

V Q b g H

g æ öæ ö

= +ç ÷ç ÷ è ø è ø Equation [1]

A discharge coefficient is introduced to account for non-ideal effects

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1 ,

2 3 2wd broad

V Q C b g H

g æ öæ ö

= +ç ÷ç ÷ è ø è ø

where , 0.65 1 /wd broad w

C H P

= +

2 A 1.2-m high broad-crested weir is used to measure the flow rate of water in a 10 m wide rectangular

channel. The flow depth well upstream from the weir is 1.8 m (measured from the bottom of the channel to the free surface). Determine the flow rate through the channel and the flow depth on the weir crest. Submit your derivation and calculations to the lab demonstrator at the start of the experiment

KNE351. Laboratory practice and assessment guidelines Page 6 of 9

KNE351 Fluid Mechanics 1: Prelaboratory Exercise (Individual: 20% of Lab Mark)

Criteria High Distinction Distinction Credit Pass Fail Score Theoretical Approach

Weighting 33.3%

Best engineering practice in terms of theoretical approach used to solve exercise.

Correct application of relevant theory to solve exercise.

Significant flaws in problem solving approach.

/5

Analysis

Weighting 33.3%

Correctly calculated all required variables and reported all of the results.

Calculations are neatly presented with appropriate significant figures and units.

Correctly calculated most of the required variables and reported all of the results.

Correctly calculated most of the required variables and reported most of the results.

Correctly calculated some of the required variables and reported some of the results.

Partial / incomplete results.

/5

Presentation of Graphical Information.

Weighting 33.3%

Graphs (where appropriate) are well presented with appropriate titles, units, gridlines and scale.

Graphs are included.

Poorly presented / incorrect graphs

/5

Comments: Mark:

  • prelab3-2018.pdf
  • Assessment-sheet.pdf