Date of Award
12-1993
Document Type
Thesis
Degree Name
M.S. in Engineering Science
First Advisor
Sumon K. Sinha
Second Advisor
Ali R. Kolaini
Third Advisor
Jeffrey A. Roux
Relational Format
Dissertation/thesis
Abstract
Stereoscopic particle tracking velocimetry (SPTV) was used to analyze a turbulent submerged jet of Reynolds number (based on the diameter of the nozzle) 8000. SPTV involves tracking the motion of tracer particles over time in a flow in three dimensions. The first part of this work consisted of developing a stereoscopic particle tracking technique using two high-speed video cameras. This included calibration of the cameras with "known" points, and developing an algorithm to automatically match and track particles. The second part was to apply the same to a submerged water jet in order to measure velocities. The velocities were subsequently used to calculate the components of the Reynolds stress tensor, vorticities and other useful turbulent parameters in all three directions at two locations along the axis of the jet. The cameras were calibrated using a set of "known" grid points which were imaged by both cameras. Data reduction equations, that relate the world coordinates (X, Y, Z positions in space) of the object (grid) points to their image coordinates in left and right cameras, were solved to obtain a set of "modified" camera parameters. The uncertainties in determining the X, Y and Z positions of the grid points, after correcting for the bias errors due to refraction and lens distortion, were found to be 6.81 x 10-5mm, 5.84 x 10-5 mm and 1.73 x 10-4 mm respectively in a 19mm x 27mm x 19mm measurement volume. Calibration and measurements were performed at two downstream locations along the axis of the jet. The corresponding measurement volumes were centered at ten and twenty nozzle diameters from the nozzle exit (x/d≡10 and 20). Polystyrene particles of 250 μm size were used to visualize the flow. A matching and tracking algorithm was developed to automatically find corresponding particles in the two views, and to track them into the next time step. Image coordinates of the particles in the stereo views were used to calculate the world coordinates of the particle. Velocities were calculated knowing the particle displacements and the elapsed time. Particle data for 100 time steps (total duration of 50 ms at x/d≡10; and 100 ms at x/d≡20) were pooled. The mean and fluctuating components of velocities were found and all components of the Reynolds stress tensor (u'2, v'2, w'2, u'v', v'w', w'u') were calculated. The vorticity field in the vertical (X-Y) plane of the jet was calculated. Integral scales were also calculated across the jet. Turbulent microscales in longitudinal and lateral directions were estimated based on the velocity fluctuations and their gradients. The mean velocity profile at x/d=22 was found to be in good agreement with the Görtler type analytical solution for the submerged round jet. A possible mechanism by which bubbles injected into the turbulent flow field undergo deformation, which may result in oscillations, was suggested. The main causes of errors in the measurement and in the particle data analysis were discussed. Possible remedies were suggested.
Recommended Citation
Rajendran, Veera P., "Development of stereoscopic particle tracking velocimetry for turbulent flow field diagnostics" (1993). Electronic Theses and Dissertations. 2184.
https://egrove.olemiss.edu/etd/2184
Accessibility Status
Searchable text