Difference between revisions of "Delft Bottle suspended load sampler"

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(Use of the Delft Bottle sampler)
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This article is a summary of sub-section 5.6.2.5 of the [[Manual Sediment Transport Measurements in Rivers, Estuaries and Coastal Seas]] <ref>Rijn, L. C. van (1986). ''Manual sediment transport measurements''. Delft, The Netherlands: Delft Hydraulics Laboratory</ref>. The Delft Bottle sampler can be used to measure the average sand transport directly.  
 
This article is a summary of sub-section 5.6.2.5 of the [[Manual Sediment Transport Measurements in Rivers, Estuaries and Coastal Seas]] <ref>Rijn, L. C. van (1986). ''Manual sediment transport measurements''. Delft, The Netherlands: Delft Hydraulics Laboratory</ref>. The Delft Bottle sampler can be used to measure the average sand transport directly.  
  
==Use of the Delft Bottle sampler==
+
==Introduction==
 
[[Image:H5625figure1.jpg|thumb|right|Figure 1: Delft Bottle sampler]]
 
[[Image:H5625figure1.jpg|thumb|right|Figure 1: Delft Bottle sampler]]
 
[[Image:H5625figure2.jpg|thumb|right|Figure 2: Delft Bottle sampler]]
 
[[Image:H5625figure2.jpg|thumb|right|Figure 2: Delft Bottle sampler]]
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The local average sediment transport (in kg/m<sup>2</sup>/s) is determined as:
 
The local average sediment transport (in kg/m<sup>2</sup>/s) is determined as:
 +
 
<math>S=\alpha\,(1-p)\rho\,_s V_s/(FT)</math> or <math>S=\alpha\,G_s/(FT)</math>
 
<math>S=\alpha\,(1-p)\rho\,_s V_s/(FT)</math> or <math>S=\alpha\,G_s/(FT)</math>
  
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: <math>G_s</math>= dry mass of sediment (mg),  
 
: <math>G_s</math>= dry mass of sediment (mg),  
 
: <math>V_s</math>= volume of sediment sample, including pores (m<sup>3</sup>),  
 
: <math>V_s</math>= volume of sediment sample, including pores (m<sup>3</sup>),  
: <math>F</math>= area of nozzle (m^2),
+
: <math>F</math>= area of nozzle (m<sup>2</sup>),
 
: <math>T</math>= sampling period (s).
 
: <math>T</math>= sampling period (s).
  
 
==Calibration==
 
==Calibration==
 
Sampling errors are introduced by:
 
Sampling errors are introduced by:
# incorrect  intake  velocity  compared  with  local  flow  velocity;  the hydraulic    coefficient    (ratio    of    intake  velocity and  local  flow velocity) varies from 1 to 1.5 ('''Dijkman, 1978,   1981'''),
+
# incorrect  intake  velocity  compared  with  local  flow  velocity;  the hydraulic    coefficient    (ratio    of    intake  velocity and  local  flow velocity) varies from 1 to 1.5 (Dijkman,  1978<ref>Dijkman,  J., 1978. ''Some Characteristics of  the USP-61 and Delft Bottle''. Delft University of Technology,  Dep.  of Civ.Eng.,  Int.  Report No. 5-78, The Netherlands</ref>, 1981<ref name="dijk">Dijkman, J., 1981. ''Investigation of Characteristic Parameters of Delft Bottle''. Delft Hydraulics Laboratory,  Report S362,  The Netherlands</ref>),
 +
 
 
# inefficiency  of  the sampler to  collect  relatively fine sediment material  (particles finer than 100 um),
 
# inefficiency  of  the sampler to  collect  relatively fine sediment material  (particles finer than 100 um),
 
# additional sampling during raising and lowering of the instrument,
 
# additional sampling during raising and lowering of the instrument,
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[[Image:H5625figure3.jpg|thumb|right|Figure 3: Calibration curves]]
 
[[Image:H5625figure3.jpg|thumb|right|Figure 3: Calibration curves]]
Usually, only the first two errors are corrected using a calibration factor a according to Figure 3, which is based on extensive laboratory measurements ('''Dijkman, 1981'''). The k-factor varies from 0.7 to 2.5 depending on the nozzle type, particle size and local flow velocity. The sampling error due to the collection of sediment particles during lowering and raising of the instrument can be reduced by using a relatively large sampling period (15 minutes). Otherwise, an additional calibration factor is necessary ('''Dijkman, 1981'''). The minimum sampling time is about 5 minutes to obtain a statistically reliable result. An additional advantage of a long sampling period is the collection of a large sediment catch enabling an accurate determination of particle size  (by sieving).
+
Usually, only the first two errors are corrected using a calibration factor a according to Figure 3, which is based on extensive laboratory measurements (Dijkman, 1981<ref name="dijk"/>). The k-factor varies from 0.7 to 2.5 depending on the nozzle type, particle size and local flow velocity. The sampling error due to the collection of sediment particles during lowering and raising of the instrument can be reduced by using a relatively large sampling period (15 minutes). Otherwise, an additional calibration factor is necessary (Dijkman, 1981<ref name="dijk"/>). The minimum sampling time is about 5 minutes to obtain a statistically reliable result. An additional advantage of a long sampling period is the collection of a large sediment catch enabling an accurate determination of particle size  (by sieving).
  
 
Field  measurements show sampling errors up to 50% for  individual samples,  even  after  the  application of  the  calibration  factor. Considering these large errors, the Delft Bottle can only be used to obtain a rough estimate of the local sand transport. Therefore, it  is sufficiently accurate to determine only the volumetric quantity of the sand sample ([[in situ]]). In that case the laboratory analysis is rather limited, which is an advantage of the Delft Bottle method. The Delft Bottle should not be used in tidal flow conditions with relatively small sediment concentrations because of the long sampling period which is required to obtain a measurable sediment catch.
 
Field  measurements show sampling errors up to 50% for  individual samples,  even  after  the  application of  the  calibration  factor. Considering these large errors, the Delft Bottle can only be used to obtain a rough estimate of the local sand transport. Therefore, it  is sufficiently accurate to determine only the volumetric quantity of the sand sample ([[in situ]]). In that case the laboratory analysis is rather limited, which is an advantage of the Delft Bottle method. The Delft Bottle should not be used in tidal flow conditions with relatively small sediment concentrations because of the long sampling period which is required to obtain a measurable sediment catch.
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===External links===
 
===External links===
 
* [http://www.wldelft.nl/rnd/intro/fields/morphology/pdf/H5-6-2-5_Delft_bottle_sampler.pdf Manual sub-section 5.6.2.5: Delft bottle sampler (pdf)]
 
* [http://www.wldelft.nl/rnd/intro/fields/morphology/pdf/H5-6-2-5_Delft_bottle_sampler.pdf Manual sub-section 5.6.2.5: Delft bottle sampler (pdf)]
 +
 +
===Further reading===
 +
Dijkman,  J. and Milisic, V., 1982. ''Investigations on Suspended Sediment Samplers''. Delft Hydraulics  Laboratory and Jaroslav Cerni  Institute,  Report S410, The Netherlands
  
 
==References==
 
==References==
 
<references/>
 
<references/>
 
'''Dijkman,  J., 1978'''. Some Characteristics of  the USP-61  and Delft Bottle. Delft University of Technology,  Dep.  of Civ.Eng.,  Int.  Report No. 5-78, The Netherlands
 
 
'''Dijkman, J., 1981'''. Investigation of Characteristic Parameters of Delft Bottle. Delft Hydraulics Laboratory,  Report S362,  The Netherlands
 
 
'''Dijkman,  J. and Milisic, V., 1982'''. Investigations on Suspended Sediment Samplers. Delft Hydraulics  Laboratory and Jaroslav Cerni  Institute,  Report S410, The Netherlands
 
 
  
 
{{author  
 
{{author  

Revision as of 17:01, 3 December 2007

This article is a summary of sub-section 5.6.2.5 of the Manual Sediment Transport Measurements in Rivers, Estuaries and Coastal Seas [1]. The Delft Bottle sampler can be used to measure the average sand transport directly.

Introduction

Figure 1: Delft Bottle sampler
Figure 2: Delft Bottle sampler

The Delft Bottle (Figures 1 and 2) is based on the flow-through principle, which means that the water entering the intake nozzle leaves the bottle at the backside. As a result of a strong reduction of the flow velocity due to the bottle geometry, the sand particles larger than about 100 um settle inside the bottle. Using this instrument, the local average sand transport is measured directly. As the overall efficiency of the Delft Bottle is rather low, it is sufficiently accurate to determine only the (immersed) volume of the sand catch on board of the vessel. A small number of the samples can be returned to the laboratory to determine the porosity factor of the sediment sample and the particle size distribution.

The local average sediment transport (in kg/m2/s) is determined as:

[math]S=\alpha\,(1-p)\rho\,_s V_s/(FT)[/math] or [math]S=\alpha\,G_s/(FT)[/math]

in which:

[math]\alpha\,[/math]= calibration factor according to Figure 3,
[math]p[/math]= porosity factor,
[math]\rho\,_s[/math]= density of sediment (2650 kg/m3),
[math]G_s[/math]= dry mass of sediment (mg),
[math]V_s[/math]= volume of sediment sample, including pores (m3),
[math]F[/math]= area of nozzle (m2),
[math]T[/math]= sampling period (s).

Calibration

Sampling errors are introduced by:

  1. incorrect intake velocity compared with local flow velocity; the hydraulic coefficient (ratio of intake velocity and local flow velocity) varies from 1 to 1.5 (Dijkman, 1978[2], 1981[3]),
  1. inefficiency of the sampler to collect relatively fine sediment material (particles finer than 100 um),
  2. additional sampling during raising and lowering of the instrument,
  3. sediment losses during removal of the sand catch from the DB.
Figure 3: Calibration curves

Usually, only the first two errors are corrected using a calibration factor a according to Figure 3, which is based on extensive laboratory measurements (Dijkman, 1981[3]). The k-factor varies from 0.7 to 2.5 depending on the nozzle type, particle size and local flow velocity. The sampling error due to the collection of sediment particles during lowering and raising of the instrument can be reduced by using a relatively large sampling period (15 minutes). Otherwise, an additional calibration factor is necessary (Dijkman, 1981[3]). The minimum sampling time is about 5 minutes to obtain a statistically reliable result. An additional advantage of a long sampling period is the collection of a large sediment catch enabling an accurate determination of particle size (by sieving).

Field measurements show sampling errors up to 50% for individual samples, even after the application of the calibration factor. Considering these large errors, the Delft Bottle can only be used to obtain a rough estimate of the local sand transport. Therefore, it is sufficiently accurate to determine only the volumetric quantity of the sand sample (in situ). In that case the laboratory analysis is rather limited, which is an advantage of the Delft Bottle method. The Delft Bottle should not be used in tidal flow conditions with relatively small sediment concentrations because of the long sampling period which is required to obtain a measurable sediment catch.

See also

Summaries of the manual

Other internal links

External links

Further reading

Dijkman, J. and Milisic, V., 1982. Investigations on Suspended Sediment Samplers. Delft Hydraulics Laboratory and Jaroslav Cerni Institute, Report S410, The Netherlands

References

  1. Rijn, L. C. van (1986). Manual sediment transport measurements. Delft, The Netherlands: Delft Hydraulics Laboratory
  2. Dijkman, J., 1978. Some Characteristics of the USP-61 and Delft Bottle. Delft University of Technology, Dep. of Civ.Eng., Int. Report No. 5-78, The Netherlands
  3. 3.0 3.1 3.2 Dijkman, J., 1981. Investigation of Characteristic Parameters of Delft Bottle. Delft Hydraulics Laboratory, Report S362, The Netherlands
The main author of this article is Rijn, Leo van
Please note that others may also have edited the contents of this article.

Citation: Rijn, Leo van (2007): Delft Bottle suspended load sampler. Available from http://www.coastalwiki.org/wiki/Delft_Bottle_suspended_load_sampler [accessed on 28-03-2024]


The main author of this article is Roberti, Hans
Please note that others may also have edited the contents of this article.

Citation: Roberti, Hans (2007): Delft Bottle suspended load sampler. Available from http://www.coastalwiki.org/wiki/Delft_Bottle_suspended_load_sampler [accessed on 28-03-2024]