Data StorageReport

Wave-induced bedform dynamics in mixed cohesive–noncohesive sediments: a fundamental re-calibration of sediment transport models in coastal environments

HYIV-HULL-06

TES,University of Hull

Author: Stuart McLelland, University of Hull

Status form

Document information

Project acronym / HYIV-HULL-06
Provider / University of Hull
Facility / TES
Title / Wave-induced bedform dynamics in mixed cohesive–noncohesive sediments: a fundamental re-calibrationof sediment transport models in coastal environments
1st user group contact (name/email) / Dr Joris, Eggenhausen,
2nduser group contact (name/email) / Dr Jaco Baas,
1st provider contact (name/email) / Stuart McLelland,
2nd provider contact (name/email) / Dan Parsons,
Start date experiment (dd-mm-yyyy) / 19-08-2013
End date experiment (dd-mm-yyyy) / 04/10/2013

Document history

Date / Status / Author / Reviewer / Approver
20/09/2014 / Final / Stuart McLelland / Dan Parsons / Stuart McLelland

Document objective

This document describes the data that was obtained during this project and how it was stored, so that others than the people immediately involved may use the data for their research.

Acknowledgement

The work described in this publication was supported by the European Community’s Seventh Framework Programme through the grant to the budget of the Integrating Activity HYDRALAB IV, Contract no. 261520.

Disclaimer

This document reflects only the authors’ views and not those of the European Community. This work may rely on data from sources external to the HYDRALAB IV project Consortium. Members of the Consortium do not accept liability for loss or damage suffered by any third party as a result of errors or inaccuracies in such data. The information in this document is provided “as is” and no guarantee or warranty is given that the information is fit for any particular purpose. The user thereof uses the information at its sole risk and neither the European Community nor any member of the HYDRALAB IV Consortium is liable for any use that may be made of the information.

Contents

1Objectives

2Experimental setup

2.1General description

2.2Definition of the coordinate system

2.3Relevant fixed parameters

3Instrumentation and data acquisition

3.1Instruments

3.2Definition of time origin and instrument synchronization

3.3Measured parameters

4Experimental procedure and test programme

5Data post-processing

6Organization of data files

6.1ABS data (Aquascat binary format)

6.2ADV data (Nortek binary format)

6.3URS data from fixed array (text format)

6.4URS data from array mounted on traverse (text format)

6.5Wave Guage data (text file format)

6.6Vectrino data (Nortek binary format)

Appendix 1: Experimental Procedure Instructions

1Objectives

The principal aim of the proposed experiments is to investigate near-bed turbulence and sediment transport interactions over rippled beds of clay-sand mixtures under waves. Such cohesive mixtures may have a yield strength that affects the timing of first appearance of bedforms from a flat sediment bed, and they are subjected to demixing (or winnowing) processes, which will in turn affect the rate of bedform development which will alter the equilibrium size and shape of the bedforms. The overall aim of this project will be achieved through three specific objectives:

1.Quantify interactions of near-bed hydrodynamics, sediment transport dynamics and turbulence over rippled beds formed by waves using state-of-the-art measurement techniques. This will help to greatly improve modelling approaches by enabling rigorous model-data comparisons, representation of near-bed turbulence behaviour, and assessment of appropriate boundary conditions.

2.Quantify how clay-sand mixtures and resultant bed cohesion affect bedform evolution, boundary layer processes (including turbulence), and sediment transport, through processes of clay winnowing and near-bed turbulence modulation. The unique results, will also allow us to directly assess scaling issues in previous work.

4.Synthesise results from objectives 1 and 2 to test the predictive ability of present state-of-the-art sediment transport models in mixed sediment environments and re-calibrate such models with the trajectories from the phase space explored within the experimental results in objectives 1-3.

2Experimental setup

2.1General description

The set-up used for these experiments was a straight 1.6 m wide and 9.8 m long, channel located in the centre of the flume. Regular water surface waves were generatedusing the two central 0.75m wide wave paddles. At the end of the flume, the waves were dissipated using perforated board with a porosity of 15%, mounted at an upstream-dipping angle of 6°. The porous slope dispersed wave energy and thus minimised wave reflections (reflections were estimated to be <10%). The floor of the channel was covered with a 0.1-m thick layer of mixed sediments with the proportion of clay and sand being varied for different experiments. The experiments used saline water (salinity: ~19 psu). Figure 2.1 shows the experimental set-up.

Five test were performed each with a different bed sediment composition.

2.2Definition of the coordinate system

The axes are defined on the drawings shown in Section 2.1. The x-axis origin is at the front of the wave paddles. The y-axis origin is located

2.3Relevant fixed parameters

The initial bed surface was always flattened. The water depth was fixed at 0.6m in all experiments. All runs used the same wave generator settings. The wave height and period were 0.19 m and 2.5 s. Based on linear wave theory, these parameters yielded a wave length of 5.7 m, a maximum near-bed orbital velocity of 0.34 ms-1, and a maximum near-bed orbital diameter of 0.13 m.

Figure 2.1:Experimental set-up

3Instrumentation and data acquisition

3.1Instruments

The following instruments were mounted on a on a frame at x = 4.3 m:

  1. optical backscatter probes (OBS1-4)
  2. downward facing acoustic backscatter probe (ABS) for measuring suspended particulate matter concentration;
  3. sampling tube connected to an ISCO sampler for collecting in situ suspended particulate matter (used for calibrating the OBS and ABS data) The vertical height of this tube could be adjusted;
  4. downward and sideways facing acoustic Doppler velocimeters (ADV0-5)
  5. a VECTRINO profiler for measuring wave orbital velocities (Only used in RUN6),
  6. an array of 4 of acoustic bed scanners (URS9-12)

Instruments were located as close as possible without causing interference.Vertical profiles were obtained for distances in the range of z = 0.03 m and 0.6 m above the initial flat bed.

Next to the fixed frame just off centre was a 3-m long traverse, on which a 2DHV acoustic bed scanner was mounted with 8 acoustic bed scanners (URS1-8) to recordspatio-temporal changes in bed height along a length of 2.5 m and spanning a width of 0.49 m.

Wave characteristics were measured with 4wave gauges, mounted along the right-lateral side of the channel

At the beginning and end of each experiment sediment cores with a diameter of 20 mm and a maximum length of 120 mm were collected from the bed.

Figure 3.1 Vertical position of instruments located on fixed frame

Figure 3.2 Horizontal locations of instrumentation (showing range of movement for UR1-8)

Table 3.1:Instrument identification and probe serial numbers

Instrument ID / Serial umber
ADV0 / N293
ADV1 / N306
ADV2 / N314
ADV3 / N288
ADV4 / N289
ADV5 / N298
OBS1 / STM1533
OBS2 / STM1530
OBS3 / STM1532
OBS4 / STM1531

3.2Definition of time origin and instrument synchronization

For each measurement period, the instrumentation mounted on the fixed frame were synchronized using an electronic pulse (except for the ISCO sampling which was controlled manually). Measurement using URS1-8 were taken separately

3.3Measured parameters

A number of parameters were measured using the instrumentation:

  1. Flow velocity
  2. Bed elevation
  3. Suspended sediment concentration
  4. Suspended and bed sediment grain size
  5. Wave height

4Experimental procedure and test programme

The first experiment (Run 01) used well-sorted, medium-grained sand with a median diameter D50=0.496 mm. For each subsequent experiment, wet kaolin clay was thoroughly mixed into the bed, so that the initial bed clay fraction, f0c, progressively increased from 3.2% (Run 03) to 5.5% (Run 06) (Table 4.1). Run 02 was a test run undertaken with irregular waves, however due to time constraints, no further irregular wave tests were undertaken. Before each run, the wet bed was flattened using a length of wood, taking care not to separate the clay and sand.

Before each experiment, these cores were collected at 7 equally-spaced locations at 3.9 m < x < 6.3 m from the wave paddles and y = 0.4 m from the right-lateral side of the channel.After draining the flume at the end of a run, sediment cores were collected from the rippled bed at 6 equally-spaced locations at 3.9 m < x < 5.9 m. These locations roughly coincided with 6 of the pre-run samples. The post-run samples comprised separate samples from the ripple crest and the ripple trough. Two additional samples were collected at (x,y) = (5.1,0.8) m and (x,y) = (5.1,1.2) m. All cores were sealed and frozen until further analysis.

  1. B.

.

Figure 4.1Location of sediment cores taken at before (A) and after (B) experiments

Waves were generated at time intervals of 20-120 minutes, depending on the bedform development rate. Instrumentation mounted on the fixed frame was started approximately 2minutes after wavemaker was started and recorded continuously until wavemaker was stopped. The wave maker was temporarily switched off for ~15 minutes to permit full scanning with URS1-8 to collect bed morphology data.

ISCO samples were collected at z = 0.05 m and z = 0.38 m in Runs 03-06. Clean sand run Run 01 had a more extensive sampling strategy, but this was not maintained in subsequent runs due to time constraints.

Table 4.1 – Experimental Runs.

Run / Initial bed sand fraction / Initial bed clay fraction / Equilibrium time / Equil. ripple height / Equil. ripple length
f0s (%) / f0c (%) / (minutes) / He (mm) / Le (mm)
01 / 100 / 0 / 35 / 18 / 122
03 / 85.4 / 3.2 / 38 / 20 / 124
04 / 77.4 / 4.6 / 53 / 22 / 119
05 / 71.2 / 5.3 / 345 / 20 / 131
06 / 71.4 / 5.5 / 510 / 20 / 121

A log file HYIV-06-LOGFILE.txt contains a record of all experimental runs including wave activation periods and instrument recording details.

The experimental procedure instructions are summarized in Appendix 1.

5Data post-processing

SPM concentrations were determined from the ISCO samples using standard filtering. The filter paper had a diameter of 47 mm and a retention of 0.7 m. Some sample were also sampled using the LISST during experiments, but a problem with the machine means these data are likely to be erroneous.

Selected cores were cut into 1-cm discs while frozen. The discs were then dried overnight at 80ºC, and processed using a Malvern 2000 Laser Particle Sizer. This provided grain size distributions, from which statistical parameters, including median particle size and bed clay and bed sand fractions, were computed.

ADV and ABS data require post-processing using appropriate software.

6Organization of data files

The data files have been uploaded to a dedicated cloud computing repository – Microsoft OneDrive (see Figure 6.1) under which all project partners have full access to the datasets generated during the experimental access period. These data sets fall under the following broad categories:

  • ABS Data
  • ADV data
  • URS data
  • Wave Gauge data
  • Vectrino Data

There are also still photographic images and video files which are organized by date

Table 6.1 shows the measurement runs and the start and end time for each measurement epoch.

Run / Epoch Number / Epoch Start Time / Epoch End Time
R01 / 1 / 000 / 020
2 / 020 / 050
3 / 050 / 080
4 / 080 / 110
5 / 110 / 140
6 / 140 / 170
7 / 170 / 200
8 / 200 / 230
9 / 230 / 260
10 / 260 / 290
R02 / 1 / 000 / 030
2 / 030 / 060
3 / 060 / 090
4 / 090 / 120
5 / 120 / 150
6 / 150 / 180
7 / 180 / 210
8 / 210 / 240
9 / 240 / 270
R03 / 1 / 000 / 015
2 / 015 / 030
3 / 030 / 045
4 / 045 / 060
5 / 060 / 090
6 / 090 / 120
7 / 120 / 150
8 / 150 / 180
9 / 180 / 210
10 / 210 / 240
11 / 240 / 270
12 / 270 / 300
R04 / 1 / 000 / 010
2 / 010 / 015
3 / 025 / 040
4 / 040 / 070
5 / 070 / 100
6 / 100 / 130
7 / 130 / 160
8 / 160 / 190
9 / 190 / 220
10 / 220 / 250
Run / Epoch Number / Epoch Start Time / Epoch End Time
R05 / 1 / 000 / 030
2 / 030 / 060
3 / 060 / 090
4 / 090 / 120
5 / 120 / 150
6 / 150 / 180
7 / 180 / 210
8 / 210 / 240
9 / 240 / 270
10 / 270 / 300
11 / 300 / 330
12 / 330 / 360
13 / 360 / 390
14 / 390 / 420
15 / 420 / 450
16 / 450 / 480
17 / 480 / 510
R06 / 1 / 000 / 030
2 / 030 / 060
3 / 060 / 090
4 / 090 / 120
5 / 120 / 150
6 / 150 / 180
7 / 180 / 210
8 / 210 / 240
9 / 240 / 270
10 / 270 / 300
11 / 300 / 330
12 / 330 / 360
13 / 360 / 390
14 / 390 / 420
15 / 420 / 450
16 / 450 / 480
17 / 480 / 510
18 / 510 / 540
19 / 540 / 570
20 / 570 / 600
21 / 600 / 630

Table 6.1. Experimental measurement epochs

6.1ABS data (Aquascat binary format)

File Directory: HYIV-HULL-06-RXX-ABSwhere XX is the run number

ABS 1-4 are recorded in files: HYIV-CW-RXX-ABSbase-TYYY-ZZZ.aqa

XX is the run number

YYY is the measurement start time

ZZZ is the measurement end time

These are ABS measurements taken prior to each epoch to estimate background suspended sediment concentrations.

ABS 1-4 are recorded in files: HYIV-CW-RXX-ABS-TYYY-ZZZ.aqa

XX is the run number

YYY is the measurement start time

ZZZ is the measurement end time

These are ABS measurements taken whilst waves are running. Measurements are synchronized with other instruments mounted on the fixed instrument frame

6.2ADV data (Nortek binary format)

Files contained in directory: HYIV-HULL-06-RXX-ADVs where XX is the run number

ADVs 0-5 are recorded in files: RXXTNNN.adv

XX is the run number

NNN is the measurement epoch number

The ADV measurements are taken whilst waves are running. Measurements are synchronized with other instruments mounted on the fixed instrument frame

6.3URS data from fixed array (text format)

File format: 4 lines showing instrument start-up; then each line contains a timestamp (HH:MM:SS.sss), followed by measurements in from each instrument in numerical order (measurements in cm), final column is a check sum.

For example

File Contents / Explanation
AN 1 / Instrument set-up
Setting number of analog channels to 1
Cmd
D
13:08:18.279 34.15 43.67 43.29 43.57 151 / HH:MM:SS.sss / URS9 / URS10 / URS11 / URS12 / Check
13:08:18.480 34.18 43.66 43.28 43.54 155 / HH:MM:SS.sss / URS9 / URS10 / URS11 / URS12 / Check
13:08:18.680 34.19 43.67 43.28 43.59 154 / HH:MM:SS.sss / URS9 / URS10 / URS11 / URS12 / Check

File contained in directory: HYIV-CW-RXX-URS-Fixed where XX is the run number

ABS 9-12 are recorded in files: HYIV-CW-RXX-URS-TYYY-ZZZ.dat

XX is the run number

YYY is the measurement start time

ZZZ is the measurement end time

These are URS measurements taken whilst waves are running. Measurements are synchronized with other instruments mounted on the fixed instrument frame

6.4URS data from array mounted on traverse (text format)

File format: 4 lines showing instrument start-up; then each line contains a timestamp (HH:MM:SS.sss), followed by measurements in from each instrument in numerical order (measurements in cm), final column is a check sum.

The format is the same as for the fixed array, except there are data from 8 URS probes.

The timestamp can be converted into distance, by dividing the measurements equally across the traverse distance of 2.5m (there is s short ramp-up and down distance at the start and end where no measurements are recorded)

File Directory: HYIV-CW-RXX-URS-Traverse where XX is the run number

Prior to each run, ABS 1-8 are recorded over at least one baseline traverse survey:

Filename:HYIV-CW-RXX-URS-BaselineN.dat

where more than 1 baseline survey is completed N increments by 1.

After each run, ABS 1-8 are recorded over for a traverse survey:

Filename:HYIV-CW-RXX-URS-PostTZZZ.dat

XX is the run number

ZZZ is the measurement epoch end time

6.5Wave Guage data (text file format)

File format: 8 lines showing set-up; the last line gives the header for the data,

each line contains, sample number, a timestamp (HH:MM:SS.sss), followed by data from 5 channels (note that channel 0 is not used). Measurements are in mV with calibration data collected each day to account for drift due to water salinity.

Files contained in directory: HYIV-HULL-06-RXX-WVGs where XX is the run number

Wave Gauges 1-4 are recorded in files: HYIV-CW-RXX-WVG-TYYY-ZZZ.csv

XX is the run number

YYY is the measurement start time

ZZZ is the measurement end time

These measurements are taken whilst waves are running. Measurements are synchronized with instruments mounted on the fixed instrument frame

Calibration data is recorded in a separate dated directory which is dated. Calibration data were collected by moving the probes to different heights in still water. Note the calibration data show significant non-linearities in the wave gauge data due to the water salinity.

Calibration files are recorded with a filename StillWater HXX (YYYmm)

XX is the height setting of the wave guage

YYY is the effective water depthabove the flume floor

6.6Vectrino data (Nortek binary format)

Vectrino data were only collected in run 6

Files contained in directory: HYIV-HULL-06-R06-Vectrino

Vectrino recorded in files: HYIV-CW-WVG-TYYY-ZZZ.aaa.bb.VectrinoProfiler.ccccc.ntk-Traverse.adv

XX is the run number

YYY is the measurement start time

ZZZ is the measurement end time

aaa, bb, ccccc are automated file labels

The Vectrino measurements are not synchronized with other instruments mounted on the fixed instrument frame

Appendix 1: Experimental Procedure Instructions

Day One; Tank set up

1 – Prepare Sediment Mix

  1. Calculate weight of clay required to reach desired clay bed fraction; account for % clay composition already in bed.
  2. Open bag of clay under water in a large bucket. Beware that too much water will increase mixing difficulty in the tank.
  3. Roughly flatted bed in flume, spread clay evenly onto surface.
  4. Mix clay into bed using hand held mixers. This may take several hours to achieve a homogenous bed. Do not knock instruments.

2 – Flatten Mixed Sediment Bed

  1. Using special purpose wooden board flatten bed to 10cm across the entire length of the tank. If increased saturation is desired use hose in lab.
  2. Be careful not to add too much water as this will result in a separation of clay.
  3. Work from up wave towards down wave.
  4. Take syringe samples from locations marked in figure 1.
  5. Fill syringe holes with mixed sediment from down wave location.
  6. Re-flatten bed local to sample holes, this may be easier with a smaller leveller.
  7. Measure clay fractions in bed, if values are significantly different further mixing may be required.

3 – Prepare Instrument Setup

  1. Put up wave ADV back in place using marks on panel wall
  2. Lower wave gauges to desired height above bed.
  3. Lower URS to desired height above bed.
  4. Move URS, ADV ect to desired position in measurement section.

4- Fill Flume

  1. Add salt to tank to reach 20 p.s.i
  2. Mix salt into water below floor level.
  3. Fill tank to 60cm’s above sediment surface.
  4. While tank is filling deploy shear vane to measure strength of bed.
  5. This will likely require the rest of the day and possibly beginning of day 2.

Day Two; Experimental day