Version 3 (modified by darelius4e, 3 years ago) (diff)

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# SLOCET

 Infrastructure CNRS_Coriolis Project (long title) Shelf sLOpe impact on Coastal Eddy Turbulence Campaign Title (name data folder) 17SLOCET Lead Author Alex Stegner Contributors Remi Laxenaire, Ted Johnson, Chunxin Yuan, Joel Sommeria, Samuel Viboud Date Campaign Start 13/02/2017 Date Campaign End 10/03/2017

# 1 - Objectives

New theoretical analyses and numerical computations have shown that regions of the continental shelf where the offshore shelf profile changes significantly can be sources of coastal eddies and thus regions of coastal turbulence. The size and intensity of the eddies is determined by the rapidity of the change in the profile and also by the stratification of the flow on the shelf. Eddies can be excited both by coastal currents (Pennel et al. 2012; Cimoli et al. 2017) passing along the shelf over the profile change and, in the correct parameter regime, by incident Topographic Rossby Waves (Rodney & Johnson 2014). A series of experiments will be carried out using PIV in both layers to demonstrate this mechanism for coastal eddy generation in two­ layer flow. The results will be compared with existing and new theory and with new numerical simulations run with the MITgcm.

# 2 - Experimental setup:

## 2.1 General description

In order to mimic the oceanic stratification a two ­layer salt stratification with a thin upper layer ( H1= 8cm) above a deep layer ( H2=72cm) is set up on the rotating platform.The ration period is fixed at To=50s (i.e. a Coriolis parameter f=4*pi/T0=0.25s-1) and adjusting the density difference rho2-rho1=10 g/l between the two layers give baroclinic deformation radius Rd around 32cm. This deformation radius will be large in comparison with the upper layer thickness ( Rd>H1) but remain small in comparison with the tank diameter D=13m. Hence, for eddies in the upper layer, we will satisfy the shallow­ water aspect ratio (H1/Reddy<<1) at meso­scale when the typical radius is of the same size or larger than Rd.

## 2.4 References axis along the wall (horizontal and vertical)

By definition we will use Ox and Oy axis to define the along shore and the cross shore axis. The central reference point (0,0) along the wall is chosen to be the closest point to the center of the tank (also labeled M0). Positive direction corresponds to the mean wave or the mean flow direction. We use seven references points along the wall to quantify the impact of the free surface deformation and the possible vertical deviation of the laser sheet.

All these points will be measured every day before starting the experiment.

 Position M2 M1 M0 M-1 M-2 H_coast (cm) H_laser_up (cm) H_laser_down (cm)

## 2.5 Fixed Parameters

 Notation Definition Values Remarks $T_0$ Rotation period $50 \ s-1$ $\Delta\rho$ Density difference $10 \ kg \ m-3$ The vertical stratification evolves in time, here we consider the maximum and minimum densities $W$ Upstream shelf width $1 \ m$ $S$ Upstream shelf slope $60%$ $\nu$ Viscosity $10-6m2s-1$ $L$ Total length of the wall $11 \ m$

## 2.5 Variable Parameters

 Notation Definition Unit Initial Estimated Values Remarks $Htot$ Total water depth $cm$ 80 estimated at the center of the wall $Hcoast$ Water depth at coast (at M0) $cm$ 20 estimated at the center of the wall $W_1$ Downstream shelf width $m$ 0-1-4 $S_1$ Downstream shelf slope $%$ 0-15-60 $T_{flap}$ Flap period $s$ 40-200 $A_{flap}$ Amplitude of carriage motion $cm$ 10-60 peak to peak amplitude $V_{flap}$ Max speed of oscillating carriage $cm/s$ 1-4 $Q_{jet}$ Flow rate of the jet $l/min$ 0.5-4

 Notation Definition Unit Initial Estimated Values $g'$ Reduced gravity $cm/s2$ 9.81 $Rd$ Baroclinic deformation radius $cm$ 32.4 $RD$ Barotropic deformation radius $cm$ 1050 $H2$ Mean lower layer depth over shelf $cm$ 46

## 2.7 Definition of the relevant non-dimensional numbers

Vertical aspect ratio (gamma), $\ gamma = H1/H2$.

Froud number (equivalent Fd), $Fd = Umax/fRd = Umax/C$.

where C is the maximum phase speed of internal gravity waves $C=sqrt(g'H1)$

Wave Froude number $Fdwave = Umax/VTRW$

where VTRW is the maximum phase speed of Topographic Rossby Wave $VTRW=???$

# 3 - Instrumentation and data acquisition

## 3.1 Instruments

Density profiler (DP)

Particle Imaging Velocimetry (PIV) A Spectra-Physics Millennia ProS 6W YAG continuous laser (532 nm) in conjunction with 3 cameras was used to provide PIV images. The laser light sheet was brought in parallel to the floor of the channel. The light sheet can then be racked in the vertical through a series of steps through the use of a motorized traverse (tilted at 3.5 degrees to match the slope of the channel) and a mirror set at 45 degrees. The laser has another set of optics to point the light sheet down at the mirror, producing the light sheet. There is a glass window that enables the laser beam to go through the surface of the water tank. A 3D animation of the laser is in the ‘videos’ subfolder of the Photos folder. The laser light sheet positions are then synchronized with the PIV cameras. The field of view extends from close to the upstream end of the first bend, towards the mid-point of the second bend.

Later experiments used larger seeding particles, 200 micron polystyrene particles for the flow seeding. These work very well for these situations where the measurement area is larger than 2 square metres. The three PIV cameras consist of one Falcon1 camera (Falcon 4M, CMOS 2432*1728 pixels, 10 bits) over the upstream part – with a 35 mm objective lens, PCO2 over the first bend with a 35 mm objective lens, and PCO3 over the most downstream part of the PIV measurement area, which has a 20 mm objective lens. 15 slices in the vertical are taken, each containing 20 images and these are repeated 10 times. Four different times between frames are used, since the velocities were not known a priori and vary as a function of height in the gravity current. So as such, no specific frame rate is used. All this is in the .xml files which can be read by a text editor. The two PCO cameras are PCO.edge5.5 CMOS cameras (2560*2160 pixels). The general approach is to have the lowest slice at approximately 2 cm above the floor, and then there are 2.5 cm heights between each successive level. These varied over time however, so there are a number of slightly different setups – see below. The sequence starts at the highest point, and then steps down through the flow, to the bottom, before switching back to the top again. Heights of laser slices (22/09/16 – 2.5 cm but after that 12/10/2016 and 14/10/2016 and 19/10/2016 all at basal 2 cm).

## 3.2 Definition of time origin and instrument synchronisation

This section relates to the main experiments, and not the test experiments (see diary entries for details of earlier experiments). Conductivity as measured in the inlet box (Probe C1) is seen to vary initially due to mixing within the input box, and because a higher input rate is used in the first minute of the experiment (~11-13 L/s in the main experiments – see Section 6) than later in the flow (~6 L/s). This initial pulse is intended to help to clear fluid out of the inlet box. The time origin is judged to be that point at which the value of this conductivity probe (C1) becomes approximately constant. The timings and synchronisation of the ADV, UVP and the Siphons are controlled with the aid of a stopwatch which is started at the time origin. PIV is then initiated soon after the time origin (approximately 0 minutes) to approximately 10 minutes run time. The timing of PIV initiation can be determined retrospectively, relative to the time origin, because the traverse initiation (that runs the ADV) is specifically linked to the time origin (ADV measurements start at 15 minutes and runs to 35 minutes), and both the traverse and the PIV are tied into the main control software. Thus knowing the time difference between the traverse initiation and the PIV initiation, and subtracting this from 15 minutes provides the PIV initiation relative to the time origin. The UVP and Siphon data are independent as their outputs are not directly tied into the Coriolis control software in the same way that the traverse is. Siphons are initiated after 5 minutes, and the cross-stream UVPs are started at 5 minutes (run until 15 minutes), whilst the downstream UVPs are started at 25 minutes are run until 35 minutes. For 19/10 and 20/10 files the start of the PIV integrates directly with the time origin, all other aspects as before. For PIV analysis, the time origin of the experiment is worked out from the C1 conductivity probe in the input box, where it exhibits the initial sharp rise (near instantaneous) as the flow input starts.

## 3.3 Requested final output and statistics

Batch processed camera data in to .png files for those experiments from 18-43 that have PIV data, so that images are in a non-proprietary format. PIV analysis of the flow field through multiple horizontal slices in different Z-positions, for the non-rotating case, and for the rotating cases (experiments 18-43 as above), dependent on the quality of the captured PIV images. Average velocity vectors for the channel slices. Potentially information on vorticity would enable the smaller-scale vortical structures that are obvious in some of the videos, to be identified.

# 4 - Methods of calibration and data processing

The MSCTI conductivity probe is calibrated after each set of experiments when the tank is drained (see Section 3.1 for full details). The ADVs have 4 heads and as such this enables some internal verification of the instrument. The ADV and UVP datasets are processed using a series of bespoke Matlab scripts. The PIV data will be processed using a bespoke script. Access to commercial PIV processing packages is also available.

The images for PIV are calibrated from images of grid put in 0_REF_FILES/Calib_absolu. The 3D calibration involves 'intrinsic parameters' of the optical system obtained from images of the same grid seen with tilt angle (put in /Calib-14-09-3D). Then rotations and translations of the calibration points are introduced to adjust the relationship between image coordinates and physical coordinates defined in section 2.2. See http://servforge.legi.grenoble-inp.fr/projects/soft-uvmat/wiki/UvmatHelp#GeometryCalib for details of the method. The calibration parameters are copied in a xml file beside each image folder with the same name (for instance PCO2.xml for PCO2/). The xml files also containing all the timing information.

All the images and processing results from the images are in the folder 0_PIV under the folder with the name of the experiment.

The images are first extracted from their initial format and written as .png images (compression with no loss of data) labelled by two indices i and j=1 to 20. The index i generally runs from 1 to 150 scanning 15 levels (then coming back to each level 1O times).

A first step in image processing after extraction is to subtract the fixed background and rescale the image intensity leading to a image folder with extension .sback. PIV results are stored as netcdf files (extension .nc) in a folder .sback.civ. These data are still in pixel displacement.

Final velocity data in phys coordinates are stored as 2D matrices under the netcdf format in folders with extension .sback.civ.mproj. They are defined on a physical grid with 1 cm mesh.

# 5 - Organization of data files

All data related to the project are in:
SERVAUTH4\share\project\coriolis\2016 or
servauth4.legi.grenoble-inp.fr\share\project\coriolis\2016

• 0_DOC: miscellaneous documentation and reports
• 0_MATLAB_FCT: specific matlab functions
• 0_PHOTOS: photos of set-up
• 0_PIV
• Each ‘PIV’ folder contains subfolders for each of the 3 PIV cameras: Dalsa (sometimes Falcon1 – it’s the same thing); PCO2; PCO3 [these are named after the different brands of camera]. Other folders include PCO2.png and PCO3.png which contain processes images of the PCO cameras that are in a non-bespoke format. Other folders that can be within the Camera folder include: Dalsa.sback; Dalsa.sback_1; PCO2.png.civ; PCO2.png.civ_1; PCO2.png.civ_2; PCO2.png.sback: PCO2.png.sback_1; PCO3.png.sback_1. .sback files refer to those files where the background has been subtracted, then civ_1 contains images with the first PIV iteration as processed in UVMAT (Joel’s code) and shows the raw data – with or without the rejected vectors; vectors are shown in four colours, blue = best, green = medium, red = poor, and pink = false. A box can be clicked to hide the false vectors. Civ_2 uses a spline interpretation to interpolate between vectors, so long as they are close enough to the surrounding vectors. Then interpolates all the vectors onto a regular grid. Times for the .png images are in the XML files, or netcdf files.
• 0_Processing: UVP processing scripts in Matlab
• 0_REF_FILES: files of general use (calibration data, grids ...)
• EXP1, EXP2, folder for each experiment with names given in the table below. The names refer to ‘fix’ for non-rotating fixed case, ‘rot’ for rotating case, ‘str1’ for the first straight position (also called position X1), and ‘apex 2’ , for the apex in bend 2 (also referred to as position X4).
• Within each experiments, there is a folder with PIV imagery called ‘Camera’, one for ADV data – ‘ADV’, one for UVP data – ‘UVP’, and one for the data coming directly off of the Coriolis table control system ‘LABVIEW’. Some experiments also contain an ‘Images’ folder or a ‘Gopro folder’ containing Gopro videos.
• Each ‘Camera’ subfolder contains subfolders for each of the 3 PIV cameras: Dalsa (sometimes Falcon1 – it’s the same thing); PCO2; PCO3 [these are named after the different brands of camera]. Other folders include PCO2.png and PCO3.png which contain processes images of the PCO cameras, that are in a non-bespoke format. Other folders that can be within the Camera folder include: Dalsa.sback; Dalsa.sback_1; PCO2.png.civ; PCO2.png.civ_1; PCO2.png.civ_2; PCO2.png.sback: PCO2.png.sback_1; PCO3.png.sback_1
• Each ‘ADV’ subfolder, contains two sub-folders: ‘nkt_files’ containing raw Nortek files, and the ‘mat_files’ are the exported raw data in Matlab format.
• Each ‘UVP’ subfolder contains two folders – one with the experiment name (which is the downstream velocity data) recorded downstream of the velocity inflection downstream of bend apex 2, and one with experiment name ‘_cross’ which contains the cross-stream UVP data recorded at bend apex ‘2. These two folders contain text files for each of the probes. The convention is that Probe 1 is the basal probe, with each subsequent probe being successively higher. There are also .mfprof files which are the raw UVP data in native format. All probes are also integrated into single Matlab files. Lastly, there is a Logfile with the header file for the UVP detailing all of the parameters used in the run.
• Each ‘LABVIEW’ subfolder contains: 1) a .lvm file which is a text file and contains a time-stamp, two voltages for the Conductivity probe on the traverse (C0 – Conductivity, and T0 – temperature [this latter one doesn’t work]), a Trig_cam heading representing the Trigger for the PIV Cameras, Conductivity probe in the input box (C1 and T1), and C2 (this was conductivity for a second probe in the input box which was briefly used before breaking. There is always a record for this but it is just background noise. 2) _position.lvm file which is an XYZ file with a times for the movement of the traverse. 3)Some folders also contain probes.nc files. These are netcdf files and contain the vector data from the processed PIV images.

# 6 - Table of Experiments:

 Exp No. Name Date_begin Hcoast W1 S1 Angle_flap T_flap A_flap Vmax_flap Q_jet d_jet dt_forcing delay dt_record Cameras $(cm)$ $(m)$ $(%)$ $(°)$ $(s)$ $(cm)$ $(cm/s)$ $(l/min)$ $(cm)$ $(s/min)$ $(s)$ $(s)$ $names$ Test Exp 1 EXP01 ?????? 17.7 1 60 90 200 60 0.9 - - 2000 / 34 0 9856.5 PCO 2 EXP02 ?????? 17.7 1 60 90 100 60 1.9 - - 3000 / 50 100 3250 PCO 3 EXP03 ?????? 17.7 1 60 90 100 30 0.9 - - 3000 / 50 50 3250 PCO 4 EXP04 ?????? 17.7 1 60 90 60 60 3.1 - - 1800 / 30 50 1850 PCO 5 EXP05 ?????? 17.6 1 60 90 40 38 3.0 - - 1200 / 20 50 1500 PCO 6 EXP06 ?????? 17.6 1 60 90 80 75 3.0 - - 2400 / 40 50 2770 PCO 7 EXP07 ?????? 17.6 1 60 90 20 20 3.1 - - 2400 / 40 50 750 PCO 8 EXP08 ?????? 17.6 1 - - - - - 7.2 60 425.5/7 0 425.5 PCO 9 EXP09 ?????? 17.6 1 - - - - - 7.4 60 1336.5/23 0 1336.5 PCO 10 EXP10 ?????? 17.6 1 - - - - - 35.3 to 60 60 2965.5/49 0 2965.5 PCO Exp Canyon 11 EXP11 22/02 11:41 18 0 0 90 60 16 0.8 - - 3000/50 50 3300 PCO/FALCON/Lumenera 12 EXP12 22/02 15:33 18 0 0 90 60 22 1.2 - - 3000/50 300 3300 PCO/FALCON/Lumenera 13 EXP13 22/02 17:09 18 0 0 90 60 36 1.9 - - 3000/50 300 3300 PCO/FALCON/Lumenera 14 EXP14 22/02 18:58 18 0 0 90 60 46 2.4 - - 3000/50 300 3300 PCO/FALCON/Lumenera 15 EXP15 23/02 10:11 18 0 0 90 60 12 0.6 - - 3000/50 300 3300 PCO/FALCON/Lumenera 16 EXP16 23/02 12:52 18 0 0 90 60 18 0.9 - - 3000/50 300 3300 PCO/FALCON/Lumenera 17 EXP17 23/02 16:25 18 0 0 90 80 30 1.2 - - 4000/67 800 4800 PCO/FALCON/Lumenera 18 EXP18 24/02 09:20 18 0 0 57.5 80 34 1.3 - - 3517/59 400 3917 PCO/FALCON/Lumenera 19 EXP19 24/02 11:27 18 0 0 57.5 60 16 0.9 - - 2220/37 780 3000 PCO/FALCON/Lumenera 20 EXP20 24/02 13:21 18 0 0 57.5 45 50 3.5 - - 1800/30 450 2250 PCO/FALCON/Lumenera 21 EXP21 24/02 14:56 18 0 0 57.5 80 32 1.3 - - 3200/53 800 3600 PCO/FALCON/Lumenera 22 EXP22 27/02 14:39 18 0 0 90 60 16 0.8 - - 2400/49 600 3000 PCO/FALCON/Lumenera 23 EXP23 27/02 16:09 18 0 0 90 60 46 2.4 - - 2400/49 600 3000 PCO/FALCON/Lumenera 24 EXP24 01/03 10:42 18 0 0 - - - - 120 30 ??? 0 ??? PCO/FALCON/Lumenera 25 EXP25 01/03 11:17 18 0 0 - - - - 80 30 ??? 0 ??? PCO/FALCON/Lumenera 26 EXP26 01/03 15:57 18 0 0 - - - - 55.8 60 ??? 0 ??? PCO/FALCON/Lumenera 27 EXP27 02/03 09:00 18 0 0 - - - - 24 60 ??? 0 ??? PCO/FALCON/Lumenera 28 EXP28 02/03 11:15 18 0 0 - - - - 25.3 60 ??? 0 ??? PCO/FALCON/Lumenera 29 EXP29 03/03 10:19 18 0 0 - - - - 56 60 ??? 0 ??? PCO/FALCON/Lumenera 30 EXP30 03/03 11:46 18 0 0 - - - - 85 60 ??? 0 ??? PCO/FALCON/Lumenera 31 EXP31 03/03 14:42 18 0 0 - - - - 120 60 ??? 0 ??? PCO/FALCON/Lumenera 32 EXP32 03/03 16:08 18 0 0 - - - - 75 60 ??? 0 ??? PCO/FALCON/Lumenera Exp Smooth Shelf 33 EXP33 08/03 14:55 19 0 0 - - - - 37.5 60 ??? 0 ??? PCO/FALCON/Lumenera 34 EXP34 08/03 16:26 19 0 0 - - - - 69 60 ??? 0 ??? PCO/FALCON/Lumenera 35 EXP35 08/03 17:56 19 0 0 - - - - 107 60 ??? 0 ??? PCO/FALCON/Lumenera

# 7 - Diary:

Wednesday, February 15th 2017

First day of experiment ! We have many difficulties to get an homogeneous distribution of particles at the level of the laser sheet (located in the dense lower layer). We first spray at the surface the particles (30 microns, 1013 g/l) diluted with quite dense salty water. But after waiting one hour the particles never reach the level of the laser sheet... Hence, in order to be able to visualize something we started to inject directly inside the lower layer with the sprayer. We then succeed to disperse high concentration of particles at the level of the laser sheet.

Three test experiments were performed with the oscillatory flap.

EXP01: Oscillation period 200s, very poor repartition of particles and hard to distinguish the global flow structure.

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 100ms 0.1 ? ?

Laser parameters

 Laser Intensity angle d-3 d-2 d-1 d0 d1 d2 d3 $(nm)$ $(Watt)$ $(°)$ $(cm)$ $(cm)$ $(cm)$ $(cm)$ $(cm)$ $(cm)$ $(cm)$ 532 25 60

EXP02: Oscillation period 100s, we starts to see some oscillation in the flow that propagates along the wall. A large-scale shear flow seems to establish along the shelf.

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.5 ? ?

EXP03: Oscillation period 100s, reduced oscillation amplitude

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.5 ? ?

Thursday, February 16th 2017

The repartition of particles over the tank is better when we arrive in the morning. During all the day, particles are added at the level of the laser beam following the same method than the previous day. The laser angle was changed from 60° to 75 °. Three interdependent parameters of the carrier can be tuned to set the forcing of the oscillating flat: T_flap, A_flap and Vmax_flap. We choose to set Vmax_flap to 3 cm/s to improve the comparison with the MITgcm simulations. Four experiments with different amplitudes and periods were performed to study the sensibility of the formation of topographic wave. In these experiments, we do not stop the record of the camera when we stop the flap to record what happen when the forcing is stopped.

EXP04: Oscillation period 60s

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.1 ? ?

Laser parameters

 Laser Intensity angle d-3 d-2 d-1 d0 d1 d2 d3 $(nm)$ $(Watt)$ $(°)$ $(cm)$ $(cm)$ $(cm)$ $(cm)$ $(cm)$ $(cm)$ $(cm)$ 532 25 75

EXP05: Oscillation period 40s

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.5 ? ?

EXP06: Oscillation period 80s

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.5 ? ?

EXP07: Oscillation period 20s

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.5 ? ?

At the end of the day, we want to perform an experiment with the laser in the upper layer but the upper limit of the laser is inside the layer of transition between the upper and lower layer. Consequently, it changes the angle of the laser due to the refraction of the beam into the inhomogeneous layer. This upper limit is fixed by the position of the mirror on which the laser beam is reflected that need to be moved when the tank is empty.

Friday, February 17th 2017

This day is dedicated to the formation of the coastal current in the upper layer.

For the moment, the control of the flow rate is complicated. It can be done by tuning the opening of one valve and estimating the flow rate in the tanks above the platform. It is done by looking at the evolution of the water levels at during 1 minute given by a stopwatch. This is not precise and it takes time to reach the flow rate targeted. We have to build and test some diaphragms to reduce the size of the pipe. Each diagram will be associated with a flow rate which will be constant.

There is no laser in the upper layer. The particles are directly mixed with the water in the tanks above the platform before their injection in the surface layer. These particles are lighted by the diffusion of the laser from below. Consequently, it is possible to see the water added by the injectors into the upper layer but all the other part of this layer are not visible. Indeed, the signal of the particle at the depth of the laser beam (i.e. in the lower layer) is too strong. This is a main problem that has to be changed by moving up the mirror which reflect the laser.

The stratification is not very good when filling from the bottom of the tank. The process will consequently be changed. The tank will firstly be filled with the salty water. The upper layer will be added directly into the surface layer using diffusers.

The laser stopped by itself during the experiment 8. This happened also shortly after the beginning of an experiment we did not save as no water injected had not enough time to reach the camera field-of-view. The problem comes from the tarpaulin of the platform which is close to the fan of the laser cooler. This blocks the evacuation of the air and increase the temperature inside the laser device. To prevent any damage, the laser is automatically shut down when a maximum temperature is reached. Now, the tarpaulin is open behind the cooler but it results in a hole letting the air to enter inside the platform. Moreover, the fan of the cooler might warm the water surface locally which can perturb the upper surface. Consequently, the cooler has to be put outside the tarpaulin to prevent all these effects.

The exit of the injector is not along the wall as it exists a gap of 20.5 cm. A large amount of the water injected turn to the right when it is injected and do not flow along the wall. This effect reduces when the flow rate is increased. It needs a flow rate by far superior (30 l/min) than what it was planned (7 l/min). Moreover, the separation of the flow due to the geometry adds a lot of perturbation that lead to the creation of large eddies. For example, a large cyclonic eddy stays close to the exit of the injector for a flow rate of 7l/min. We need to prevent this effect adding a wall between the onshore part of the injector and the wall. This solution was tested with a wooden sheet hold by hand which seems to drastically reduce this effect. A fixed one will be added when the platform will be empty on Monday.

All the different problems mentioned before will be solved when the platform will be empty on Monday. Three experiments were performed but, as the flow is perturbed in many ways, we do not think that it will be representative of the flow when the different problems will be solved.

EXP08: Injection flow rate 7.2 l/min

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.5 ? ?

EXP09: Injection flow rate 7.4 l/min

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.5 ? ?

EXP10: Injection flow rate 35.3 l/min to 60 l/min. We increased the flow rate from 35.3 l/min to 60 l/min after XXXX minutes of recording the see its impact on the formation of the coastal current.

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO after carriage 50ms 0.5 ? ?

Monday, February 20th 2017

The platform is empty in the morning.

The day begins by the calibration of the two CTD sensors using 7 samples which span from 998.6 to 1025.1 kg/m3. One 2nd order polynomial regression is applied for each of them to define the relation between the voltage measured and the water density. The profiles obtained are presented in the following figure.

All the distance between each element of the experimental setup and the point of reference along the wall are measured. A schematic of the setup of the first week called smooth shelf configuration is presented in the following figure.

The three downstream plastic sheets were removed to replace them by a triangle which make the transition between the slope and the flat floor. Along the wall, it results in 6.75m of constant shell, 2.74m of transition and 3.27m of flat bottom.

The calibration of two of the three fixed cameras is also done using a target of 2mx2m in the field of view of each of them. Firstly, the target is kept horizontal for the first pictures. Then, it is moved in all directions to have a 3D representation of the target that help to correct the picture. This calibration is not done for the camera recording the flap and the injector as we did not succeed to have a clear picture in the computer.

We saw last week that a lot of turbulence is created at the exit of the injector. A schematic of what was observed is presented in the following figure.

To prevent these perturbations, the shelf is extended and now the exit of the injector is above the shelf to ensure that the water flow directly above it. Secondly, a vertical plastic sheet that link the exit of the injector and the wall is added. We hope that this will prevent the return of the current below the injector and will help the injected water to reach directly the vertical wall.

Tuesday, February 21th 2017

The position of the carrier is changed. The flap is now linked to the downstream edge of the carrier to improve the field of view in the cameras upstream of the transition area.

The laser length is now changed to 90°. The mirror of the laser is also lifted of 8cm to have the laser sheet in the upper homogeneous layer. The laser device is also rotated to have enough light both over the transition area and over the flat bottom.

All the distance between each element of the second experimental are measured. A schematic of the setup of the second week in the canyon configuration is presented in the following figure.

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 18 H_laser_up (cm) H_laser_down (cm)

Wednesday, February 22th 2017

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 19.7 19 18 18.5 19 H_laser_up (cm) / / / / / H_laser_down (cm) 9.5 3.5 4 7.3 /

A CTD profile recorded this morning can be compared to the one recorded at the end of the day yesterday in the following figure :

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 19 18 18.5 18 18.8 H_laser_up (cm) / / / / / H_laser_down (cm) 6 2.5 3.5 5 /

Bottom density => 1009.5 (T 20.9) Surface density => 1002 (T 19.9)

 LumeneraSettings mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness gain EXP12 283 1.83 4000x1600 200 2.33 39 4.43 EXP13 283 1.83 4000x1600 200 2.33 39 4.43 EXP14 545-560 1.83 4000x1600 200 2.33 39 4.64

Thursday, February 23th 2017

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 19 18.7 18 18 18.5 H_laser_up (cm) / / / / / H_laser_down (cm) / 6.6 3.4 2.5 /

Changeemnt de sonde aprés EXP15, C0 est déplacé et maintenant devient C2. La nouvelle sonde C0 est à la place de l'ancienne C0. Surface nouvelle C0/TO 371 surface libre. C2 est ajoutée aux données lors de l'expérience 17. Le gain de cette dernière est modifié aprés 5min de cette même expérience.

 LumeneraSettings mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness gain EXP15 550-560 1.83 4000x1600 200 3.26 39 4.43 EXP16 550-560 1.83 4000x1600 200 3.26 39 7-9 EXP17 570 1.83 4000x1600 200 3.26 39 13

Friday, February 24th 2017

Position of the flap changed in the morning. A schema of the two positions is given in the following figure.

 LumeneraSettings mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness gain EXP18 576 1.83 4000x1600 220 3.26 39 3.64 EXP19 576 1.83 4000x1600 220 3.26 39 3.9 EXP20 577 1.83 4000x1600 220 3.26 39 3.9 EXP21 599 1.83 4000x1600 220 3.26 38.6 7

EXP18: Oscillation

Problem of data recording with the PCO camera during the experiment 18. First 4'35 of the record were not stored due to a lack of disk space.

We stopped the recording before the end of the experiment as the number of particles was not sufficient.

EXP19: Oscillation

EXP21: Oscillation period 80s

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO/FALCON/Lumenera before carriage 50ms 0.3 ? ?

Monday, February 27th 2017

The extraction of the surface layer during the weekend did not succeed. 15 cm of water was extracted but there is still a stratification on the profiles.

The remaining water is mixed by hand and the 15 last centimetres are added using water with the density of the bottom layer. The final density is 1009.1 g/m^3 at 20.2°C. The difference of height with two layers stratification is less than 1 mm.

Checked the horizontal of the laser sheet.Change the flat position to have its reference perpendicular to the wall.

The mixing of the water re-suspend the particles in all the water column. The repartition is now homogeneous but they are in all different layers but not only at the position of the laser sheet. The resulting pictures are less complicated to interpret by eyes because the fronts are less obvious.

EXP22: Oscillation Barotropic period 60s amplitude 16cm

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO/FALCON/Lumenera before carriage 50ms 0.3 ? ?

EXP23: Oscillation Barotropic period 60s amplitude 46cm

 Cameras location exposure dt size avg scale $(ms)$ $(s)$ $pix.pix$ $pix/cm$ PCO/FALCON/Lumenera before carriage 50ms 0.3 ? ?

The recycling of the water is started at the end of the day.

Wednesday, March 1st 2017

Injector, reduction of its surface

EXP23: Inejctor diaphragm 19mm "

EXP24: Inejctor diaphragm 15mm "

We test the relation between the flow rate $Q[L/min]$ and the diameter of the diaphragm $D[mm]$. The relation gives the following figure.

 LumeneraSettings mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness gain EXP24 320 1.44 4000x1800 220 3.26 39 3.64 EXP25 320 1.44 4000x1800 220 3.26 39 1.8-10

'

Thursday, 2 of March 2017

 LumeneraSettings mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness gain EXP27 322 1.1 4000x1800 220 3.26 39 1-8 EXP28 322 1.1 4000x1800 220 3.26 39 1-8

Dist from surface =>1=>Hcoast=18cm Laser_surf=3.4cm; -1=>LAser_surf=3.2cm, 0=>Hcoast=18cm LAser_surf=5.2cm

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 18?? 18 18 H_laser_up (cm) 14.6 12.8 14.8 H_laser_down (cm)

Samuel starts the day by calibrating ultrasound probes. He also changed on probe (Acq 3. Third from the wall). Values are stored in the file : calib probe 02/03. He different positions are : 0/-0.5/-1/+1/+0.5/0

Profile made this morning is presented in the following figure.

EXP27=> change of the laser position at 09.39.

Friday, 3 of March 2017

 LumeneraSettings mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness gain EXP29 320 1.18 4000x1800 220 3.26 39 1-8 EXP30 320 1.18 4000x1800 220 3.26 39 1-8

We lifted the ultrasound sensors of 42mm.

EXP29 =>10h19 13 D (FPS 3)

Mooving of the sensor closer to the wall

EXP30 =>11h46 16 D (FPS 10)

EXP31 =>14h42 19 D (FPS 10)

EXP32 =>16h08 15 D (FPS 10)

Wednesday, 8 of March 2017

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 19 18 H_laser_up (cm) 15 14.3 H_laser_down (cm)

EXP33 =>14h55 10.5 D (FPS 3) Problems with the camera PCO at the beginning. We need to compare the date of the first record with the trigger to obtain its time of start (~15h08).

Changement de vanne suite à une fuite.

EXP34 =>16h26 15 D (FPS 3) Problems with the camera FALCON at the beginning. Delay of 201 frames with Dalsa2

EXP35 =>17h56 19 D (FPS 3) Problems with the camera FALCON at the beginning. Several start of the trigger recorded are not representative of the start of the camera.

 LumeneraSettings mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness gain EXP29 320 1.18 4000x1800 220 3.26 39 1-8 EXP30 320 1.18 4000x1800 220 3.26 39 1-8

Thursday, 9 of March 2017

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 19.5 19.7 18.2 H_laser_up (cm) 17 16 15.5 H_laser_down (cm)

Lumenera Settings

 mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness gain EXP36 322 1.15 4000x1800 150 3.26 39 1-8 EXP37 310 1.2 4000x1800 200 1.7 37 2-9 EXP38 310 1.2 4000x1800 200 1.7 37 10-12

EXP36 =>[11h09:The 11h09]:50 The laser sheet before the wall pass through a clean (light) fluid layer without particles. This new option provides a significant increase of the intensity of illuminated particles in the experimental area !! Good option to keep for the next experiments.

Diaphragm 9mm / flow rate 24 lit/min

EXP37 => 14h12:30

Diaphragm 11.5mm / flow rate 33 lit/min (?? strange value according to the previous fit)

The position of lumen era camera was changed for this experiment and new calibration done.

Very nice upstream current with a well defined unstable wavelength on the steep slope.

EXP38 => 15h58

Diaphragm 13mm / flow rate 55 lit/min

Very nice upstream current with a well defined unstable wavelength on the steep slope. We test in the middle of the acquisition the laser sheet in the lower layer (-13cm). It confirms that the velocity in the lower layer is very weak.

Friday, 10 of March 2017

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 20 20 19 H_laser_up (cm) 19 17 16 H_laser_down (cm)

Lumenera Settings

 mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness EXP39 310 1.2 4000x1800 200 1.7 37 1-8 EXP40 310 1.2 4000x1800 200 1.7 37 17 EXP40video2 311 1.2 4000x1800 100 1.7 37 14 EXP41 311 1.2 4000x1800 100 1.7 37 17 EXP42 311 1.2 4000x1800 100 1.7 37 17-20 EXP43 311 1.2 4000x1800 100 1.7 37 13-16 EXP43_2 176 1.2 4000x1800 50 2.8 46 23

We start today with a frontal density current (like a buoyant river plume). In other words the injection of fresh water in a deepd fluid layer of uniform density.

EXP39 start injection around =>09h20

Diaphragm 9mm / flow rate 24 lit/min

fps of PCO, DALSA, FALCON stays at 3 images/s

A very thin (small width) current flow along the wall, no apparent signature of instability or any meander formation . But due to the curvature of the laser sheet we didn't see what happens at the same depth everywhere... we are quite deep at the center (M0) of the wall while much closer to the surface at (M1 and M-1).

EXP40 =>10h06

Diaphragm 13mm / flow rate 54 lit/min

Always a stable density front with almost no impact of the bottom shelf bathymetry...

We forget to take a density profile inside the current ! grrr...

EXP41 =>10h!37:55

fps of PCO, DALSA, FALCON was changed to 10 images/s and for all the records below

Diaphragm 15mm / flow rate 75lit/min

Always a stable density front with a slight change on the width of the current from steep to gentle slope, but not sure that it is note due to the curvature of the laser sheet ...

EXP42 =>11h!05:55

Diaphragm 17mm / flow rate 88 lit/min

Always a stable density front with a slight change on the width of the current from steep to gentle slope, but not sure that it is note due to the curvature of the laser sheet ...

Several density profiles were done inside the coastal front.

EXP43 =>14h!32:30

Diaphragm 19mm / flow rate 120 lit/min

A roughly stable front with some few meanders or stretched eddies at the edge of the front.

Wednesday, 15 of March 2017

 Position M2 M1 M0 M-1 M-2 H_coast (cm) 6.6 6.9 7 H_laser_up (cm) 4.6 2.1 4 H_laser_down (cm)

Lumenera Settings

 mean_dt(ms) mean_dx(pix/mm) Area(pix/pix) exposure(ms) contrast brightness EXP44 1.2 4000x1800 150 2.8 46 6-10 EXP45 1.2 4000x1800 17 EXP46 1.2 4000x1800 14 EXP47 1.2 4000x1800 200 2.8 46 14

EXP44 =>08h48 fin 9h28

Diaphragm 9mm / flow rate 24 lit/min

A clear stagnation point occurs along the coast where the bathymetric slope changes. The impact of the bottom bathymetry is significantly stronger now.

On the other hand with the 40s period of rotation there is more vibration of the platform which may affect the stability of the recording cameras.

EXP45 =>10h10 fin ?

Diaphragm 13mm / flow rate 48 lit/min

The coastal current (and the eddies) pass over the bathymetric change without any stagnation points

EXP46 => 11h49 end 12h26

Diaphragm 10.5mm / flow rate 34.5 lit/min

Here again a stagnation point appears at the change of the bathymetric slope and the coastal flow is strongly reduced along the wall on the gentles slope area.

EXP47 =>14h11 end 15h00

Diaphragm 7.5mm / flow