Flow past a swirler grid - PIV data from wind tunnel at Re 1.3 × 10^4 and 2.7 × 10^4

Description

Particle Image Velocimetry (PIV) measurement of flow past a swirler grid. This grid is designed to produce a regular system of clock-wise and anti-clock-wise vortices, which alternate in a same way as black and white squares on a chessboard. These longitudinal vortices are relatively stable and they play as a energy source at larger distances past the grid. Therefore, the maximum of turbulent kinetic energy (TKE) lies in the distance of ~ 10 × M (the mesh parameter). - File "MeasuredPlanes.png" for general overview. The PIV is in Stereo configuration (so called 2D 3C). - File "SwirlerGrid.scad" is the geometry (CAD), to open and modify that file, You will need open-source program OpenSCAD, https://openscad.org/. The geometry is described in more details in a function sample: https://www.kke.zcu.cz/cs/Research/function_samples (in Czech language) - File "StereoPIV.zip" contains the measured data. They are organized in folders named e.g. "t05msX02", where "t05ms" means wind tunnel velocity of 5 m/s and "X02M" signifies the stream-wise distance in multiplies of M. Each such folder contains about 500 individual snapshots in ".csv" files, which are exported from Dantec Dynamic Studio. The data start at line no. 10. The column description is in line no. 9, velocity data are in columns 5 - 7, where 5th column (headed "U") represents the velocity in horizontal direction, i.e. y-axis in Figure "MeasuredPlanes.png"; 6th column (headed "V") is vertical z-velocity and 7th column (headed "W") is the stream-wise x-component.

Steps to reproduce

- The swirler grid (file "SwirlerGrid.scad") is produced by using 3D printer Prusa Mk 2.5 from polymerized lactic acid (PLA) of black color; printing temperature 215°C, heated bed 60°C, nozzle diameter 0.4 mm, filament diameter 1.75 mm. - Wind tunnel is in detail described in our work Yanovych (2019) "Research of a wind tunnel parameters by means of cross-section analysis of air flow profiles", AIP Conference Proceedings vol. 2189 no. 020024, doi: 10.1063/1.5138636. The test section has size of 305 × 203 mm, length 760 mm (740 mm transparent). The velocity is controlled via back-loop from pressure drop across the contraction section. The measured plane is at the outlet of the test-section and different stream-wise positions are realized by moving the grid upstream. The grid is fixed inside the test section by 4 screw rods. - Time between laser pulses is 50 μs (for velocity 10 m/s) or 100 μs (for velocity 5 m/s) respectively. The pair repetition frequency is 7.4 Hz, which is limit of the PIV cameras Flow Sense Mk II.

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