Experiments in Fluids

, Volume 19, Issue 3, pp 173–187 | Cite as

The evolution of initially uniform shear flow through a nearly two-dimensional 90° curved duct

  • H. J. Lim
  • M. K. Chung
  • H. J. Sung


An experimental study has been made in a nearly two-dimensional 90° curved duct to investigate the effects of interaction between streamline curvature and mean strain on the evolution of turbulence. The initial uniform shear at the entrance to the curved duct was varied by an upstream shear generator to produce five different shear conditions; a uniform flow (UF), a positive weak shear (PW), a positive strong shear (PS), a negative weak shear (NW) and a negative strong shear (NS). The variations of surface pressure and the mean velocity profiles along the downstream direction under different initial shears are carefully measured. The responses of turbulent Reynolds stresses and triple velocity products to the curvature and the mean strain are also investigated. The evolution of turbulence under the curvature with the different shear conditions is described in terms of the turbulent kinetic energy and the various length scales vs the angular distance θ or a curvature parameters S c which is defined by S c = (U/R)/(dU/dy- U/R). The results show that the turbulent kinetic energy and the integral length scale are augmented when S c < 0.054 whereas they are suppressed when S c > 0.054. It is also observed that the micro-length scales of Taylor and Kolmogoroff are relatively insensitive to the curvature.


Turbulent Kinetic Energy Reynolds Stress Angular Distance Shear Condition Downstream Direction 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of Symbols


wall static pressure coefficient, \(C_{pw} = 2(P - P_{{\text{ref}}} )/{}_\rho U_c^2\)


duct width = 190 mm


turbulent diffusion


duct height = 600 mm


turbulent kinetic energy, k = \(\overline {q^2 }\)/2


streamwise integral length scale or duct length


characteristic length scale


normal distance from curved surface


wall static pressure


wall static pressure at x = 8D


pressure fluctuation


{ovu}2 + {ovv} + {ovw}2




radius of curvature


Reynolds number based on U c and D, \({\text{Re}}_D = U_c D/v\)


ratio of curvature strain to straight mean strain, \(S = (U/R)/(dU/dy)\)


ratio of curvature strain to total mean strain, \(S_c = (U/R)/(dU/dy - U/R)\)



U, V, W

mean velocity components in x,y,z coordinates, respectively


centerline mean velocity at x = 8D

u, v, w

velocity fluctuations in x,y, z coordinates, respectively


characteristic velocity scale

{ovu}2, {ovv}2, {ovw}2

Reynolds normal stresses in the x,y,z coordinates, respectively


Reynolds shear stress

{ovu}3, {ovv}3, {ovu}2{ovv}, {ovuv}2

triple velocity products

x,y, z

streamwise, transverse and spanwise coordinates

Greek symbols


boundary layer thickness




Kolmogoroff micro-length scale


Taylor micro-length scale


kinematic viscosity


pressure-velocity correlation term


flow angle in curved duct


density of air


non-dimensional development time, \(\tau = (x/U)|dU/dy|\)


modified non-dimensional development time, \(\tau _c = (x/U)|dU/dy - U/R|\)



initial value at θ=10°, y/D =-0.1


surface wall


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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • H. J. Lim
    • 1
  • M. K. Chung
    • 1
  • H. J. Sung
    • 1
  1. 1.Department of Mechanical EngineeringKorea Advanced Institute of Science and TechnologyTaejonKorea

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