2nd DA Challenge Case 1 Datasets

Physical situation

This test case considers the square duct DNS simulations of Pirozzoli et al. (2018), to study a fully  developed turbulent flow. The figure below illustrates the simulation results, conducted at a bulk Reynolds number of Reb = 2hub/nu = 40,000 and a friction Reynolds number Retau approximately equal to 1,000, where h denotes the duct half-width, ub is the bulk velocity and nu the fluid’s kinematic viscosity.

Visualization of square duct flow DNS

 

For the challenge, a domain of h x h x h is considered, where x denotes the streamwise direction, and y = 0 and z = 0 are the duct walls. A virtual experiment is conducted in water (rho = 1000 kg/m3, nu = 1 . 10-6 m2/s), with h = 100 mm and ub = 0.2 m/s. The experimental setup is sketched below, including the four-camera arrangement for the LPT challenge. A cloud of virtual particles, hypothesized as fully passive tracers, has been propagated within the DNS simulation.

Input data

This test case of the DA challenge consists of the reconstruction of the velocity and pressure fields from scattered positions of particles. Simulated results from time-resolved (TR) acquisitions, four-pulse (FP) recordings and two-pulse (TP) recordings are considered. For each, seeding density is varied over 0.001 ppp, 0.01 ppp, 0.05 ppp and 0.2 ppp.

Input files

The particles’ positions in 3D space and the particles’ IDs are given in ASCII files. The first three columns of the data files correspond to the instantaneous X, Y, Z particle coordinates respectively (given in mm). The particles within the same track are identified with the particles/track ID (4th column). The data files have a header composed by three lines:

  1.    Title = Snapshot #

  2.   Variables = X Y Z PartID
  3.     Zone I= , F=POINT

The parameter I indicates the number of particles present in Snapshot #n.

TR cases

A sequence of 50 consecutive frames (starting at 0) is provided for each seeding density case. The time separation between snapshots is 5.916 ms. The file naming follows the convention:

DA_CASE01_TR_ppp_0_AAA_PartFile_BBBB.dat

where AAA is the fractional value of the seeding density in ppp (e.g. 010 for 0.01 ppp images), and BBBB is the snapshot number (from 0000 to 0049).

FP cases

The particles belonging to each of the four pulses of the sequence are provided for every seeding density case. The timing template of the four-pulse acquisition is 2-1-2, with the unitary separation of 5.916 ms. This means that the time separation between the first and second pulse is 11.832 ms, the separation between the second and third pulses is 5.916 ms, and finally between the third and fourth pulses is again 11.832 ms. The file naming follows the convention:

DA_CASE01_FP_ppp_0_AAA_PartFile_BBBB.dat

where AAA is the fractional value of the seeding density in ppp (e.g. 001 for 0.001 ppp images), and BBBB is the pulse number (from 0000 to 0003).

TP cases

The particles belonging to each of the two pulses of the sequence are provided for every seeding density case. The time separation between pulses is 5.916 ms. The file naming follows the convention:

DA_CASE01_TP_ppp_0_AAA_PartFile_BBBB.dat

where AAA is the fractional value of the seeding density in ppp (e.g. 200 for 0.2 ppp images), and BBBB is the pulse number (from 0000 to 0001).

Requested output and formatting rules

Common to all cases: submission form and zip archive

Clicking on one of the "Submit results" buttons 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.

Requested data and file formatting

The results need to be prescribed on a Cartesian grid with constant spacing of 1 mm in each direction. The following ranges are requested:

  •      X: 101 grid points, from x = 0 to x = 100 mm
  •      Y: 100 grid points, from y = 0.1 to y = 99.1 mm
  •     Z: 100 grid points, from

     z = 0.1 to z = 99.1 mm

corresponding to a total number of 1,010,000 grid points.

The output variables required on this grid are the following (total of 16 variables):

  • Grid nodes: X, Y, Z in mm
  • Velocity components: VX, VY, VZ in m/s
  • Velocity gradient components: dVXdX, dVXdY, dVXdZ, dVYdX, dVYdY, dVYdZ, dVZdX, dVZdY, dVZdZ in 1/s
  • Static pressure: p in Pa

where the pressure variable refers to the relative pressure with respect to the point (X,Y,Z) = (0,0.1,0.1) mm.

In order to ease file transfer, output files are requested in HDF5 format. In order to avoid confusion, the space coordinates are expected to vary in the order: X, Y and then Z, i.e. X corresponding to the innermost loop and Z to the outermost loop.

TR cases

The flow field at timestep 24 (from the sequence starting at 0) needs to be supplied for each seeding density situation. Providing the output also at timestep 2 is optional. The file name has to follow:

ZZZZ_DA_CASE01_TR_ppp_0_AAA_PartFile_BBBB.h5

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), AAA is the fractional value of the seeding density in ppp (e.g. 001 for 0.001 ppp images) and BBBB is the snapshot number (e.g. 0002 or 0024).

FP cases

The flow field at the time in the middle of the second and third pulses (centre of the sequence) needs to be supplied for each seeding density situation. The file name has to follow:

ZZZZ_DA_CASE01_FP_ppp_0_AAA.h5

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), AAA is the fractional value of the seeding density in ppp (e.g. 001 for 0.001 ppp images).

TP cases

The flow field at the time in the middle of the two pulses needs to be supplied for each seeding density situation. The file name has to follow:

ZZZZ_DA_CASE01_TP_ppp_0_AAA.h5

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), AAA is the fractional value of the seeding density in ppp (e.g. 001 for 0.001 ppp images).

Contact in case of any questions: Andrea Sciacchitano, TU Delft: a.sciacchitano@tudelft.nl

References

Pirozzoli, S., Modesti, D., Orlandi, P., & Grasso, F. (2018). Turbulence and secondary motions in square duct flow. Journal of Fluid Mechanics, 840, 631–655. doi:10.1017/jfm.2018.66