Surface Velocity Fields from Experiments in Flow Through Emergent Vegetation

Description of the CG2019 - Surface PIV dataset.

The dataset presented in this entry is the used for the analysis included in the paper

Corredor-Garcia J.L., Delalande A., Stovin V., Guymer I. (2020) On the Use of Surface PIV for the Characterization of Wake Area in Flows Through Emergent Vegetation. 
In: Kalinowska M., Mrokowska M., Rowiński P. (eds) Recent Trends in Environmental Hydraulics. GeoPlanet: Earth and Planetary Sciences. Springer, Cham. https://doi.org/10.1007/978-3-030-37105-0_4 

GENERAL INFORMATION

This dataset comprises the spatial and temporal velocity fields obtained from Surface PIV experiments in emergent artificial vegetation, obtained in the Guntt flume at the University of Warwick. The experiments were carried out by Alexandre Delalande and the data was ultimately analysed and formatted by Leonardo Corredor. The experiments involved the use of the following equipment.

- Camera: Panasonic LUMIX DMC-GX80
- Lens: Panasonic H-FS12032/G VARIO 12-32mm F3.3-5.6 ASPH OIS with Polarizing filter
- Illumination: 500 LED Ultra Bright 5500 K Panel (35.5x20.3x10.0 cm)
- Seeding Material: Buoyant glass particles
Based on this characteristics, the original Surface PIV (SPIV) images had a resolution of 3840x2160 pixels, with a frequency of 25 fps.

The data was obtained from 4 flow tests under uniform flow conditions, with the characteristics described in Table 1 of the paper referenced above. 

The SPIV images were processed using PIVlab - using 4 window passes with the smalles one being 8x8 pixels - and post-processed (i.e. outliers removed) according to the methodology described in the paper. These results, presented in the attached dataset can be described as follows.

FILE NOMENCLATURE AND STRUCTURE

Nomenclature:

The velocity information for each test is fractioned into multiple .mat files (i.e. binary MATLAB® files) to improve readability. The .mat files are named according to the following convention:

CG2019_SPIV_TestXX_XX.mat

The prefix 'CG2019_SPIV' identifies the entire dataset and should be read with reference to Corredor-Garcia (2019) and Surface PIV.

TestXX: indicates what test that data belongs to. The Test number is defined as in Table 1 of the reference paper.

The last 2 elements XX indicate what portion of the data for that test is included in the file.

Structure:

Each of the .mat files contains the following MATLAB-native arrays:

- MASK: two-dimensional matrix representing the locations of the masks for the SPIV images. Remember that by mask it is meant obstructions in the flow field that are not included in the velocity calculation.

- MASKfilt: multidimensional array (y, x, t) including the mask for each instantaneous velocity map

- T : array containing the time stamp (i.e. instant) when each instantaneous velocity map was obtained.

- Uraw : multidimensional array (y, x, t) containing the RAW longitudinal/streamwise velocity values for each instantaneous velocity map. By raw it is meant the data that was obtained from PIVlab, but to which no further post-processing was applied.

- Vraw : multidimensional array (y, x, t) containing the RAW transverse/lateral velocity values for each instantaneous velocity map. By raw it is meant the data that was obtained from PIVlab, but to which no further post-processing was applied.

- Ufilt : multidimensional array (y, x, t) containing the POST-PROCESSED longitudinal/streamwise velocity values for each instantaneous velocity map. The post-processing is the one described in the reference paper.

- Vfilt : multidimensional array (y, x, t) containing the POST-PROCESSED transverse/lateral velocity values for each instantaneous velocity map. The post-processing is the one described in the reference paper.

- X : two-dimensional array containing the streamwise/longitudinal coordinate of point in the velocity maps.

- Y : two-dimensional array containing the transverse/lateral coordinate of point in the velocity maps.

Note: the raw velocity data was included to allow the user to try their own outlier-removing/post-processing/filtering method.
 
UNITS

The dataset is presented with the following units

Velocity data (Uraw, Vraw, Ufilt, Vfilt) is presented in m/s (metres/second)

Time (T) is presented in seconds

Spatial data (X, Y) is given in metres.



Jesus Leonardo Corredor Garcia