1st LPT Challenge datasets | ONERA flow reconstruction benchmarks

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

Schematic of the location and extent of the measurement domain, together with the definition of the coordinate system

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, and C the camera number, the latter labelled from 0 to 3.

3. Requested cases and formatting rules for upload

3.1. TP case

3.1.1. Mandatory cases

Results should be submitted at least for seeding densities equal to 0.005, 0.025, 0.05 and 0.08 ppp. 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.

3.1.2. Preparing your upload

Please replicate the contents of the sample archive myAlgo_LPT_TP.zip:

Results for each seeding density should be stored in an ASCII file with 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.
File naming convention (as above): myAlgo_LPT_TP_ppp_0_AAA.dat, with AAA the fractional value of seeding density in ppp and "myAlgo" a string that can be chosen freely, but without any space in it.
Once your files are ready, as in the example above, please zip them directly into a single archive. Please make sure that you do not zip a folder containing the results, as this will result in the submission being rejected.

3.2. TR case

3.1.1. Mandatory cases

Results should be submitted at least for seeding densities equal to 0.005, 0.025, 0.05, 0.08 and 0.12 ppp. 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.

Important: the requested snapshot number depends on the seeding density value: time step 41 (images ‘_I0040’) shoud be provided for ppp ≤ 0.12, while time step 91 (images ‘_I0090’) is expected for ppp ≥ 0.16.

3.1.2. Preparing your upload

Please replicate the contents of the sample archive myAlgo_LPT_TR.zip:

Results for each seeding density should be stored in an ASCII file with first line equal to 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. There is no specific convention about number formatting.
File naming convention (as above): myAlgo_LPT_TR_ppp_0_AAA.dat, with AAA the fractional value of seeding density in ppp and "myAlgo" a string that can be chosen freely, but without any space in it.
Once your files are ready, as in the example above, please zip them directly into a single archive. Please make sure that you do not zip a folder containing the results, as this will result in the submission being rejected.

3.3. Upload form

Once your zip archive is ready, clicking on "Submit TP results" or on "Submit TR results" will open a form allowing you to upload a file containing your results.

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:

List of authors (default: submitter name)
Authors' institution(s) (default: submitter institution)
Optional: departement / team (default: submitter's departement / team)
Algorithm's short name or acronym
Algorithm's full name
Optional: URL address of the publication on your algorithm, or of a webpage describing it

For these fields, note that rules apply, in terms of maximum length and/or authorized characters. These are displayed on the form in the explanatory text of each field. In particular, commas are not allowed in any of the above fields.

Contact in case of questions: Benjamin Leclaire, ONERA: benjamin.leclaire@onera.fr