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Cutthroat Flume Accuracy

The Cutthroat flume was developed to provide accurate flow measurement with a precision of +/-3% under free-flow conditions.

This accuracy is to be expected when the ratio of flow depth (at the point of measurement) to flume length is between 0.1 and 0.4.  Above 0.4 and higher approach velocities and rapid changes in the water surface introduce inaccuracies.

Cutthroat Flow Equations

For free-flow conditions, the level-to-flow equation for the Cutthroat flume can be expressed as:

free flow discharge equation for Rectangular Cutthroat flume

Length

Width

n

K (Imperial)

(SI) C (Imperial)

(SI)

18”

1"

2.150

6.100

7.4791 0.494

0.1802

18”

2"

2.150

6.100

7.4791 0.974

0.3553

18”

4"

2.150

6.100

7.4791 1.975

0.7205

18”

8"

2.150

6.100

7.4791 4.030

1.4701

 

36"

2"

1.840

4.500

3.7758 0.719

0.1811

36"

4"

1.840

4.500

3.7758 1.459

0.3675

36"

8"

1.840

4.500

3.7758 2.970

0.7503

36"

16"

1.840

4.500

3.7758 6.040

1.5213

 

54"

3"

1.720

3.980

2.9394 0.960

0.2103

54"

6"

1.720

3.980

2.9394 1.960

0.4293

54"

12"

1.720

3.980

2.9394 3.980

0.8718

54"

24"

1.720

3.980

2.9394 8.010

1.745

 

108"

12"

1.560

3.500

2.1383 3.50

0.6322

108"

24"

1.560

3.500

2.1383 7.11

1.2843

108"

48"

1.560

3.500

2.1383 14.49

2.6175

108"

72"

1.560

3.500

2.1383 22.0

3.9741

 

Cutthroat Flume Flow Tables 

Free-flow discharge tables for Cutthroat flumes can be found in the Discharge Tables section.