Journal of Visualization

, Volume 1, Issue 1, pp 9–28 | Cite as

Flow visualization of relaminarization phenomena in curved pipes and the related measurements

  • Kurokawa M. 
  • Cheng K. C. 
  • Shi L. 


Flow visualization results for secondary flow phenomena at the exit of 90° and 180° bends and helically coiled pipes (1, 2 and 5 turns), (radius of curvatureR c=381 mm, inside pipe diameterd=37.5 mm, curvature ratiod/2R c=0.049) and in the downstream straight pipe (l/d=30) are presented to study the stabilizing (relaminarization) effect in curved pipes with fully developed entry turbulent air flow and the destabilizing (re-transition from laminar to turbulent flow) effect in the downstream straight region. The entry Reynolds numbers areRe=2200, 3200, 4300 and 5300).

The related measurement results using a hot-film anemometer are presented for developing profiles of the time-mean streamwise velocity distribution and the axial turbulence intensity field in the 180° return bend and in the downstream straight pipe for Reynolds numbersRe=3200, 4300, 6300 and 8200.

The time traces showing the output of the hot-film sensor are also presented for developing fluctuating velocity field in the 180° bend and in the downstream straight pipe for the same Reynolds number range. Some aspects of the relaminarization phenomena in curved pipes and the re-transition phenomena from laminar to turbulent flow in the downstream straight pipe are clarified by the present experimental investigation.


laminarization curved pipes visualization measurements 



inside pipe radius,d/2


inside pipe diameter, 2a


Dean number, Re (a/R c)1/2


downstream tube length


radius of curvature for bend or coil


Reynolds number,u md / v


time-mean local axial velocity


fluctuating axial velocity component


mean velocity across the cross-section


horizontal and vertical coordinates (Fig⨴3)


axial coordinate in downstream pipe


kinematic viscosity of air


bend or coil turn angle


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Copyright information

© The Visualization Society of Japan 1998

Authors and Affiliations

  • Kurokawa M. 
    • 1
  • Cheng K. C. 
    • 1
  • Shi L. 
    • 1
  1. 1.Department of Mechanical EngineeringUniversity of AlbertaEdmontonCanada

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