Experiments in Fluids

, Volume 14, Issue 1–2, pp 85–96 | Cite as

Swirling turbulent flow through a curved pipe

Part I: Effect of swirl and bend curvature
  • M. Anwer
  • R. M. C. So


An experimental study of a swirling turbulent flow through a curved pipe with a pipe-to-mean-bend radius ratio of 0.077 and a flow Reynolds number based on pipe diameter and mean bulk velocity of 50,000 has been carried out. A rotating section, six pipe diameters long, is set up at six diameters upstream of the curved bend entrance. The rotating section is designed to provide a solid-body rotation to the flow. At the entrance of the rotating section, a fully-developed turbulent pipe flow is established. This study reports on the flow characteristics for the case where the swirl number, defined as the ratio of the pipe circumferential velocity to mean bulk velocity, is one. Wall static pressures, mean velocities, Reynolds stresses and wall shear distribution around the pipe are measured using pressure transducers, rotating-wires and surface hot-film gauges. The measurements are used to analyze the competing effects of swirl and bend curvature on curved-pipe flows, particularly their influence on the secondary flow pattern in the crossstream plane of the curved pipe. At this swirl number, all measured data indicate that, besides the decaying combined free and forced vortex, there are no secondary cells present in the cross-stream plane of the curved pipe. Consequently, the flow displays characteristics of axial symmetry and the turbulent normal stress distributions are more uniform across the pipe compared to fully-developed pipe flows.


Pipe Flow Pipe Diameter Bulk Velocity Swirl Number Curve Pipe 
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List of symbols


calibration constant


bridge voltage


bridge voltage at zero flow


total skin friction coefficient, = 2 τw/ρ W 0 2


pipe diameter, = 7.62 cm


Dean number, = α1/2 Re


angular momentum


calibration constant


swirl number, = ΩD/2 W0


radial coordinate


mean bend radius of curvature, = 49.5 cm


pipe Reynolds number, = DW0


axial coordinate along the upstream (measured negative) and downstream (measured positive) tangent

U, V, W

mean velocities along the radial, tangential and axial directions, respectively

u, v, w

mean fluctuating velocities along the radial, tangential and axial directions, respectively

u′, v′, w′

root mean square normal stress along the radial, tangential and axial directions, respectively

v{ov2}, u{ov2}

normal stress along the tangential and radial direction, respectively


mean bulk velocity, ∼ 10 m/s

Wc W

measured at pipe axis


total wall friction velocity, \(\sqrt {\left( {\tau _w /\varrho } \right)} \)

\(\left( {w_\tau } \right)_s \)

total wall friction velocity measured at S/D = -18

ū,v vw, w7#x016B;

turbulent shear stresses


pipe-to-mean-bend radius ratio, = D/2 R = 0.077


axial coordinate measured from bend entrance


fluid kinematic viscosity


fluid density


mean total wall shear stress

\(\tilde \tau _w \)

instantaneous total wall shear


azimuthal coordinate measured zero from pipe hori zontal diameter near outer bend


angular speed of the rotating section


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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • M. Anwer
    • 1
  • R. M. C. So
    • 1
  1. 1.Mechanical and Aerospace EngineeringArizona State UniversityTempeUSA

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