Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
권호 표지
DOI QR코드

DOI QR Code

A Study on the Near Wake of a Square Cylinder Using Particle Image Velocimetry (III) - Phase Average -

PIV기법을 이용한정사각실린더의 근접후류에 관한 연구 (III) - 위상평균유동장 -

  • Published : 2001.11.01
Download PDF
⟨ Previous Next ⟩

Abstract

Phase averaged velocity fields in the near wake region behind a square cylinder have been (successfully) obtained using randomly sampled PIV data sets. The Reynolds number based on the flow velocity and the vertex height was 3,900. To identify the phase information, we examined the magnitude of circulation and the center of peak vorticity. The center of vorticity was estimated from lowpass filtered vorticity contours (LES decomposition) adopting a sub-pixel searching algirithm. Due to the sinusoidal nature of firculation which is closely related to the instantaneous vorticity, the location of peak voticity fits well with a sine curve of the circulation magnitude. Conditionally-averaged velocity fields represent the barman vortex shedding phenomenon very well within 5 degrees phase uncertainty. The oscillating nature of the separated shear layer and the separation bubble at the top surface are clearly observed. With the hot-wire measurements of Strouhal frequency, we found thats the convection velocity changes its magnitude very rapidly from 25 to 75 percent of the free stream velocity along the streamwise direction when the flow passes by the recirculation region.

Keywords

References

  1. Reynolds, W. C. and Hussain, A. K. M. F., 1972, 'The Mechanics of an Organized Wave in Turbulent Shear Flow, Part 3. Theoretical Models and Comparison with Experirnents.,' J Fluid Mech., Vol. 54, pp. 263-288 https://doi.org/10.1017/S0022112072000679
  2. Perry, A. E. and Watmuff, J. H., 1981, 'The Phase-Averaged Large-Scale Structures in Three Dimensional Turbulent Wakes.,' J Fluid Mech.. Vol. 103, pp. 33-51 https://doi.org/10.1017/S0022112081001225
  3. Owen, F. K. and Johnson. D. A.. 1980, 'Measurements of Unsteady Vortex Flow Fields.,' AIAA J. Vol. 18, No. 10, pp. 1173-1179
  4. 김경천, 정양범, 1994, '가열된 원주후류의 열성층 영향에 대한 연구,' 대한기계학회 논문집, 제18권, 제6호, pp. 2454-2464
  5. Kim, K. C., 1997, Proceedings of the 11th International Heat Transfer Conference, Vol. 3, pp. 305 - 310
  6. Lourenco, L., Subramanian, S. and Ding, Z., 1997, 'Time Series Velocity Field Reconstruction from PIV Data.,' Meas. Sci. Technol., Vol. 8, pp. 1533 - 1538 https://doi.org/10.1088/0957-0233/8/12/016
  7. Kim, K. C., Yoon, S. Y., Kim, S. K. and Boo, J. S., 2000, 'Phase Averaged Velocity Field Reconstruction from PIV Data Using a Vortex Tracking Method : Near Wake of a Circular Cylinder,' ASME Fluids Engineering Conference, Boston, June 11-15, USA. Vol. 123, pp. 379 - 398
  8. Okajirna, A., 1982, 'Strouhal Numbers of Rectangular Cylinders,' J Fluid Mech., Vol. 123, pp. 379-398 https://doi.org/10.1017/S0022112082003115
  9. Lyn, D. A., Einav, S., Rodi, W. and Park, J. H., 1995, 'A Laser-Doppler Velocimetry Study of the Ensemble-Averaged Characteristics of the Turbulent Near Wake of a Square Cylinder.,' J Fluid Mech., Vol. 304, pp. 285-319 https://doi.org/10.1017/S0022112095004435
  10. Yoon, S. Y., 1999, 'PIV Measurements in the Turbulent Near Wake of a Circular Cylinder', MS. Thesis. Pusan National University
  11. Westerweel, J.. 1993, 'Digital Particle Image Velocimetry- Theroy and Application.,' PhD thesis, Delft University of Technology, The Netherlands