Friday 04/07/08
1 hour of .8m, 6s waves with sea and lagoon at 2.5m
Instruments reset, and SRP/ADV downloaded
Cilia sourced a more suitable auger – we will reinstall the PTs on Monday
Series C6 - .8m, 6s, sea=2.5m, lagoon=3.5m (any more and too much water pours out of the beachface and causes rill erosion)
Normal sequence of [5,5,5,5,10,10,15,15,20,5 mins mono]
Response of the beach was to steepen and slight berm accretion. Stabilised very quickly
Matlab worked fine for the video measurements
Lawrence got more information about the wave generation with respect to steering signal, water depth, reflection compensation etc, and started to write a short report on the Deltaflume paddle modis operandi
Andre and Charlie worked on data analysis scripts for the ADV and SRP data, respectively, in order for us to do quick checks on the quality of the data, and also get some information whilst we are here.
No reset – will do the same as yesterday because the profile is steep then flattens considerably in the region of wave breaking. Therefore it is likely that the waves again wont breach the berm sufficiently.
Test run – beach steepened even more, and position of the berm cut back approx 1m.
At start of default waves, PT stick 17.5cm from bed. At end was 17cm off bed. Top PT (-10cm) exposed at surface.
The response of the profile was to erode and steepen the beachface and accrete the berm. Some bedforms started to develop seawards of the breakers around 75-80m (1—2 crests)
Monday 07/07/08
30 mins of Hs=0.8m, 6s, 2.5 sea and 2.5 lagoon. Did desired job of reshaping the profile so the beachface was not so steep. ‘Reset’ run again not desired because waves breaking further offshore, and boundary conditions should ideally not change when wave parameters are not changing (only lagoonal levels)
Instrument heights fixed, sediment photos taken. Top subsurface pt still flush with the bed.
On offshore rig, SRP is 43cm above the Sontek ADV probe bottom to middle axis of SRP. New vectrino (delft) is 25cm above the lower vectrino (soton) probe bottom to probe bottom
PT 12 was replaced. It was quite an effort to dig down through the gravel with the tools provided. Used combination of low lagoon levels, vacuum cleaner, and soil augers to drill down 1.8m, where the replacement pt was installed at 1.8m + 0.18m (1.62m), which was believed to be always below the water table. Insufficient time for the installation of PT 8 so that will occur tomorrow when the offshore rig is replaced in the flume. Only levelled the new PT approximately in order not to waste any more time, so it was approximated, and a uniform offset will be worked out at the end and will be applied to the data once acquired.
Series C5 – 0.8m, 6s, 2.5 sea, 1.5 lagoon
The response of the profile was to move material from breaker zone and seawards of the breaker zone and move it onshore to create uniform sedimentation on the beachface. The bedforms around 75-80m seawards of breakpoint developed into 3—4 distinct crests with spacing of around 1m.
The run finished very late so it was decided to keep the run going over night so the PTs could log whilst the groundwater levels equilibriated, and also to check the levels of the new PT that was installed earlier on but not checked. To prevent the files from becoming too large, the run was stopped and restarted (called seriesC5 and seriesC5a, respectively).
Tuesday 08/07/08
Instruments moved out of way of the forthcoming profile reset
Sediment photos
Barrier profile reset using 10s 80cm waves for 2min. Did not achieve desired effect of berm flattening, so we used rakes and shovels to push the material down the slope. We then sent 10s 1m waves down the flume for 2mins, which pushed a little material onshore, but had the desired effect of flattening the profile sufficiently for runs to continue
With some considerable effort again, PT 8 was reinstalled – the distance from pt sensor to bed was 2.03m.
Some issues with synching one vectrino laptop with time server – not able to do it wirelessly. Resolved by plugging the laptop into the last remaining Ethernet port on the hub of the timeserver laptop
Offshore rig was reinstated into the flume at 72.5m, - fibreglass poles were both 40cm above water surface. Rig placed closer inshore because of interesting ripples (1m wavelength, 30cm height) which had developed in this area (some 5m seawards of breakpoint) over the last 2 experimental runs. Instruments were programmed to start recording at 14:00:00
SRP – 1 minute swaths, continuously as before
ADV – 25Hz, as deployment before
Series B2 began at c.15:00
[5,5,5,5,10,10]. Built a small berm around rig 2. Will finish the run in the morning, and the offshore rig will be removed, checked, and programmed for a longer run
Vectrino trial logging with synchronisation – vectrinos were synced and the master vectrino logged data ok, but the slave did not log data (the file didn’t appear even though it said it was logging in the software). Jon and Dan resolved this problem so a repeat trial will be made in the morning when series B2 gets under way again.
The data from the EMs and PTs looked a little dodgy – blocky. Dan noticed and stopped the data collection momentarily, restarted LabView data acquisition software, and logged again for the rest of the run. Will check the data tonight.
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