First LPT Challenge datasets
The present page describes the input data as well as rules for submitting results (with corresponding download/upload links in the left panel). For more information about the virtual camera system, and the physical domain, see the First Challenge description page.
Published results are presented in dedicated pages for the two-pulse and time-resolved cases.
1. Domain of interest and setup
As depicted in the figure above, the region of interest for the challenge starts 35 mm downstream of the cylinder centre, and is a parallelepipedic domain of 100 mm×50 mm×30 mm (streamwise × spanwise × wall-normal). In span, it is centred and covers half of the numerical domain; in the wall-normal direction, it starts at the lower wall.
The virtual setup consists of illumination with a limited extension in the streamwise and wall-normal directions (simulating the use of a slab), on a cross-section in XZ of 100x30 mm² extending along the Y axis, and of a set of four cameras viewing the measurement volume mainly from above (Z-direction) onto the XY-planes. The cameras are located along the X axis at Y=0 at a height of about Z=600 mm with a viewing angle of (+30,+10,-10,-30) degrees relative to the Z axis. The measurement volume of 100x50x30 mm3 is nearly completely visible by the four-camera system, with only some extra particles outside the measurement volume visible in the Y direction (up to about +/- 35 mm).
Each camera sensor is made of 1920 x 1200 pixels with a 10 µm pitch. Pixel position (0,0) corresponds to the centre of the pixel located at the top left corner of an image. The calibration parameters correspond to a basic camera pinhole model with focal length f=100 mm without any extra optical distortion. Some typical camera noise is added to the images. A constant particle image size (PSF or OTF) is used.
2. Input data
2.1. Camera calibration and physical domain
Camera calibration can be performed by using the "Camera calibration data" button on the left panel. This downloads an ASCII file called CalibPoints.txt, in which each line contains the coordinates of a point in the domain together with its projections on the four cameras:
X Y Z x1 y1 x2 y2 x3 y3 x4 y4
where (X,Y,Z) are the point coordinates in units of mm and (xi,yi) the coordinates of its projection on camera i in units of pixel.
2.2. Cases and images
Regardless of the TP or TR case, subsequent images are separated by an inter-frame time Dt = 600 µs, corresponding to a maximum of about 7 pixel displacement in the camera images. All images are stored in 16-bit TIFF compressed format. For both cases as well, the varying parameter is the seeding density expressed in particles per pixel (ppp).
2.2.1. TP Case
The zip archive contains images corresponding to seeding densities equal to 0.005, 0.025, 0.05, 0.08, 0.12 and 0.16 ppp (one folder per density). For each density, one pair of images is given for each camera. Images names are built on model
TP_ppp_0_AAA_IBBBB_C.tif
where AAA is the fractional value of the seeding density in ppp (e.g. 160 for 0.16 ppp images), BBBB is the pulse number (0000 and 0001), and C the camera number, the latter labelled from 0 to 3.
2.2.2. TR case
The zip archive contains images corresponding to seeding densities equal to 0.005, 0.025, 0.05, 0.08, 0.12, 0.16 and 0.2 ppp (one folder per density). Depending on the density, a set of either 50 (0.005, 0.025, 0.05, 0.08, 0.12 ppp) or 100 subsequent images (0.16 and 0.2 ppp) is provided for each camera. Images names are built on a similar model as for the TP case, i.e.
TR_ppp_0_AAA_IBBBB_C.tif
where AAA is the fractional value of the seeding density in ppp (e.g. 160 for 0.16 ppp images), BBBB is the pulse number (0000 and 0001), and C the camera number, the latter labelled from 0 to 3.
3. Requested cases and formatting rules for upload
3.1. Common to all cases: submission form and zip archive
Clicking on "Submit TP results" or on "Submit TR results" will open a form allowing you to upload a file containing your results. In either case, this file should be a zip archive (.zip extension), containing directly (no folder) one result file per seeding density, each being an ASCII file (see further precisions regarding file naming and format in the paragraphs below).
The upload form should also be filled with the following information, which is used for result presentation only if you choose to publish your result based on the evaluation sent by email:
- the short name or acronym of the algorithm used for data processing (should match with the prefix name of your result files, see below). This name should have a length of 24 chars maximum, and contain no space. Authorized chars are alphanumeric chars and one of the following: [ ] _ - @
- the full name of the algorithm. This name should have a length of 100 chars maximum, and should not contain commas.
- Optionally, you may provide the URL address of the publication (if any) about your algorithm, or of a webpage describing it
- If needed (e.g. in the situation where the algorithm is due to a collaboration between two or more institutions), you can correct the name of the Institution which will appear in the public result tables (set by default to your institution). For this field, the maximum length is of 24 chars and commas are not allowed.
3.2. TP case
Each result file within the zip archive should respect the following naming convention
XXXXX_TP_ppp_0_AAA.dat
where XXXXX corresponds to the acronym / short name of your algorithm (3 characters minimum, no space, only [A-Z0-9a-z]_-@ chars) as indicated in the corresponding field of the upload form (i.e. both should match, including for upper and lower case letters), and AAA is the fractional value of the seeding density in ppp as for the image files.
The format of each ASCII result file should be as follows: first line equal to
X0 Y0 Z0 X1 Y1 Z1
followed by one line for each particle with the two measured particle positions X0, Y0, Z0 and X1, Y1, Z1 in mm for time steps t0 and t1. There is no specific convention about number formatting. A sample archive with example files is avaialable for download (case of an algorithm with short name myAlgo).
The zip archive should mandatorily contain result files at least for seeding densities equal to 0.005, 0.025, 0.05 and 0.08 ppp (note that this is slightly different from the actual 1st LPT Challenge). Any incomplete submission will be rejected. Additionally to these mandatory densities, participants are also encouraged to process other ones. In that case, all densities up to the highest one chosen should be supplied.
3.3. TR case
Each result file within the zip archive should respect the following naming convention
XXXXX_TR_ppp_0_AAA.dat
where XXXXX corresponds to the acronym / short name of your algorithm (3 characters minimum, no space, only [A-Z0-9a-z]_-@ chars) as indicated in the corresponding field of the upload form (i.e. both should match, including for upper and lower case letters), and AAA is the fractional value of the seeding density in ppp as for the image files.
For each seeding density, the ASCII file should contain the flow field for either time step 40 (images ‘_I0040’, ppp ≤ 0.12) or 90 (images ‘_I0090’, ppp ≥ 0.16). Its format should be as follows: first line
X Y Z Xfit Yfit Zfit VX VY VZ AX AY AZ
followed by one line for each particle track with raw position X, Y, Z in mm, fitted position (i.e. associated to the estimation of velocity and acceleration) Xfit, Yfit, Zfit in mm, the velocity VX, VY, VZ in m/s, and the acceleration AX, AY, AZ in m/s2, all calculated at time step 40 or 90 depending on the seeding density of the case.
The zip archive should mandatorily contain result files at least for seeding densities equal to 0.005, 0.025, 0.05, 0.08 and 0.12 ppp (note that this is slightly different from the actual 1st LPT Challenge). Any incomplete submission will be rejected. Additionally to these mandatory densities, participants are also encouraged to process other ones. In that case, all densities up to the highest one chosen should be supplied.