Changes between Version 68 and Version 69 of WikiStart


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Oct 23, 2017, 2:16:16 PM (3 years ago)
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steiger5na
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    4444
    4545== 2.3.2 Reference axis for ice front experiments ==
     46By definition we will use Ox and Oy axis to define the along channel and cross channel axis. The central reference point (0,0) is chosen to be at the front of the ice shelf and in the middle of the channel. Positive u - direction corresponds to the flow direction towards the ice shelf and positive v - direction is directed to the "west".
     47
     48
     49
    4650== 2.4 References axis along the wall (horizontal and vertical) - Nadine add image! ==
    4751By 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.
     
    9599'''Conductivity Sondes (CS)'''
    96100
    97 '''Particle Imaging Velocimetry (PIV)''' ''A Spectra-Physics Millennia ProS 6W YAG continuous laser (532 nm) in conjunction with 2 cameras was used to provide PIV images. The laser light sheet was brought in parallel to the bottom of the tank. 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.''
    98 
    99 ''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).''
     101'''Particle Imaging Velocimetry (PIV)''' A Spectra-Physics Millennia ProS 6W YAG continuous laser (532 nm) in conjunction with 2 cameras was used to provide PIV images. The laser light sheet was brought in parallel to the bottom of the tank in case of the slope front experiments and tilted by 2% to match the slope of the channel in case of the ice front experiments. The light sheet can then be racked in the vertical through a series of steps through the use of a motorized traverse 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. The laser light sheet positions are then synchronized with the PIV cameras. The laser light sheets cover the whole topography, but are slighlty bended towards the sides, so that they are closer to the bottom at the source and at the end of the topography compared to the middle. Also a vertical laser was used together with a vertical camera to observe the flow in a cross section. The three PIV cameras consist of:
     102- one Falcon1 camera ''(Falcon 4M, CMOS 2432*1728 pixels, 10 bits)'' as the vertical camera – with a 35 mm objective lens.[[BR]]
     103
     104- PCO1 (PCO.edge5.5 CMOS cameras (2560*2160 pixels)) with a 35 mm objective lens overlooking the part in front of the source in the slope front experiments and the ice shelf in the ice front experiments.[[BR]]
     105
     106- PCO2 (PCO.edge5.5 CMOS cameras (2560*2160 pixels)) with 20 mm objective lens overlooking the continental self and trough in the slope front experiments and the channel in the ice front experiments.[[BR]]
     107
     108After experiment 26 of the slope front expriments, 60 micron particles were used for the flow seeding. The number of slices were adjusted to the need of the experiment and is listed in the file LIST_OF_EXPERIMENTS.xlxs. The number of slices, dt between the images, exposure time (either 20-50), the number of images and the number of scans had to be decided before each experiments. The slope front experiments also contained series of images at one horizontal slice to better observe the evolution of the flow. The vertical laser was turned on after a steady flow was established/ at the end of the experiment.
     109
     110During horizontal PIV, the vertical camera was turned on (with the same acquisition as the PCO1 and PCO2) to produce an .xml file that contains information on the time, dt, exposure time, times for the scanning. During some experiments, this .xml file was missing (technical mistake or if we stopped the acquisition before it was done), so that .xml files from other experiments have to be used and modified to fit the setup. However, the starting time is not correct then.
     111
    100112
    101113== 3.2 Definition of time origin and instrument synchronisation ==
     
    128140
    129141For the vertical calibration the images are saved in a different file format with extension '.seq'. The format can be changed in the UVMAT software, but the folder with the vertical images should not be renamed (e.g. '2017-09-08T16.04.32'). To change the image format, choose RUN -> Field Series. Chose the right input file, an select 'extract_rdvision.m', click INPUT and RUN. The image will be saved in a new folder as a .png file and is ready for use in UVMAT.
     142
     143===Laser sheet calibration===
     144==Slope front experiments==
     145||Laser setting||$H_{real}||||
     146||650||55 cm||
     147||700||49.5 cm||
     148||800||40 cm||
     149||850||35 cm||
     150||900||30 cm||
     151
     152==Ice front experiments==
     153
     154
    130155
    131156=== Probes calibration ===
     
    187212
    188213== 5.4 How to process the data ==
    189 All experiments are saved in fsnet>project>coriolis>2017>17ICESHELF>DATA>EXPXX. The  file EXPXX is for the horizontal laser sheet, EXPXX_SCAN is for the  horizontal scanning and EXPXX_VERT for the vertical sheet.  Within each EXPXX you will get three files : FALCON, PC01 and PC02.  These are the three cameras we are using during the experiments, the  FALCON is the camera for the vertical sheet and will only be used to get  the time parameters. The data from the PC01 and PC02 need to be treated  in order to perform the ''PIV''.
     214All experiments are saved in fsnet>project>coriolis>2017>17ICESHELF>DATAZ>EXPXX. DATAZ corresponds to DATA for the slope front experiments and to DATA2 for the ice shelf experiments. The file EXPXX is for the horizontal laser sheet, EXPXX_SCAN is for the  horizontal scanning and EXPXX_VERT for the vertical sheet.  Within each EXPXX and EXPXX_SCAN you will get three files : FALCON, PC01 and PC02.  These are the three cameras we are using during the experiments, the  FALCON is the camera for the vertical sheet and will only be used to get  the time parameters. The data from the PC01 and PC02 need to be treated  in order to perform the ''PIV''.
    190215
    191216 1. '''Copy the files from the computer of the cameras'''. [[BR]]- The images from the vertical camera are saved on the local computer in G: and have to be copied into the folder FALCON in the corresponding experiment. [[BR]]- The images from ''PCO1'' (camera at the inflow) are saved on D: of the remote desktop connection that ends with ''151''. The images have the be copied into the folder ''PCO1'' of the corresponding experiment.[[BR]]- The images from ''PCO2'' (camera above the trough) are saved on D: of the remote desktop connection that ends with ''150''. The images have to be copied into the folder ''PCO2'' of the corresponding experiment.
    192217 1. '''Get the .xml file with timing information'''[[BR]]In uvmat select the Run>field series then open>browse and select an experiment. Go in the folder within the FALCON and select the ''.seq'' file. Choose ''extract_rdvision_times'' in the Action part, click on Input and Run. This will create a ''Falcon.xml ''within the FALCON folder. '''Check that the Falcon.xml file contains the right information on Dti (time between two images), Exposure time and Number of images (!NbDti)! '''
    193  1. '''Convert .tif into .png[[BR]]'''In Run>Field series you can open any ''.tif'' of the desired folder (Warning : you should not take the im.tif but any im@XXXX.tif is working). Then in the ''Action'' part you should select ''extract_multitif'', if the Input button is in pink you should click on it and give to the software the'' Falcon.xml'' that you extracted earlier (If that doesn't exist, copy one ''.xml'' file from a previous experiment and change the seting manually. Once it is done you can click on RUN, don't forget to select ''cluster_oar'' in the run mode, the action will be much faster. When it is done a new folder called PCOY.png is created in your EXPXX folder and contains all the png. [[BR]]For''' SCANS''': Check that the right number of slices is registered! To do so, click on ''check_data_files'' in the'' Action'' part and type the right number of slices in ''nb_slices i''
     218 1. '''Convert .tif into .png[[BR]]'''In Run>Field series you can open any ''.tif'' of the desired folder (Warning : you should not take the im.tif but any im@XXXX.tif is working). Then in the ''Action'' part you should select ''extract_multitif'', if the Input button is in pink you should click on it and give to the software the'' Falcon.xml'' that you extracted earlier (If that doesn't exist, copy one ''.xml'' file from a previous experiment and change the setting manually. Once it is done you can click on RUN, don't forget to select ''cluster_oar'' in the run mode, the action will be much faster. When it is done a new folder called PCOY.png is created in your EXPXX folder and contains all the png. [[BR]]For''' SCANS''': Check that the right number of slices is registered! To do so, click on ''check_data_files'' in the'' Action'' part and type the right number of slices in ''nb_slices i''
    194219 1. '''Remove background'''[[BR]]Browse for the right experiment again and chose the extracted ''.png'' images. The action ''sub_background'' that will remove all the motionless structures.  For the input you have to make sure that the ''image rescaling coefficient'' is equal to 2 and then make is run. (This process takes a long time, don't forget to make it run on the cluster). You can check on ''Status'', how many images are done. The output of this action is a file PCOY.png.sback filed with png images.[[BR]]For''' SCANS: '''Here, the ''image rescaling coefficient'' should be equal to 0! Also, set the ''Number of images for sliding background'' to the number of images per slice!
    195220 1. '''Do PIV[[BR]]'''Browse for the images with the removed background''' '''(PCOY.png.sback.). Choose the Action ''civ_series''. For in Input, you have to import an existing .xml file to get the right parameters. You can use one .xml file from another experiment on which the piv is already done. Browse for: EXPXX/PCOY.png.sback.civ/0_XML and choose any of the img_#.xml. Make sure in the Input parameters that you chose the correct mask (right camera and with/without corner).
     
    211236 * ''0_PHOTOS: photos of set-up''
    212237 * ''0_PIV''
    213    * ''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.''
     238   * ''Each ‘PIV’ folder contains subfolders for each of the 3 PIV cameras: Dalsa (sometimes Falcon1 – it’s the same thing); PCO1; PCO2 [these are named after the different brands of camera]. Other folders include PCO1.png and PCO2.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.''
    214239
    215240 * ''0_Processing: UVP processing scripts in Matlab''