Developing Flow in a Curved Rectangular Duct
Experiments by Kim and Patel
- Developing turbulent flow in a 90 deg. curved duct of rectangular cross-section.
- Duct with two straight and one curved sections.
- Rectangular cross-section of the duct with a width of H = 20.3 cm and
a height of 6H.
- Inner radius of curvature of the bend: Ri = 3×H.
- Straight upstream section with a length of 7.5H = 1.52 m.
- Straight downstream section with a length of 25.5H = 5.18 m.
The initially 2D boundary layers developing on the vertical lateral walls are subjected
to strong streamwise curvatures and associated pressure gradients along the bend. On the
other hand, the pressure-driven secondary motion in the corner regions eventually leads to
the formation of a longitudinal vortex on the convex wall. The duct aspect ratio is such
that these two features of the flow develop more or less independently, without
- Air with a kinematic viscosity:
=1.45 × 10-5 m2/s.
- Freestream velocity at station U1 (x = -4.5H):
Uo = 16 m/s.
- Reynolds number: UoH/ = 224,000.
At station U1 (x = -4.5H), the velocity is uniform in the core flow,
outside the boundary layers, within a deviation less than 1%. On the vertical
lateral walls, the boundary layers are of flat-plate type with a momentum thickness
Reynolds number of 1650, a boundary layer thickness of
= 0.08H and a friction coefficient of Cf = 0.0038. The 2D
wind-tunnel contraction located 3H upstream of U1 introduces a secondary motion in the boundary
layers on top and bottom flat walls but its magnitude reaches only 5% of the
freestream velocity. The following measurements are then provided for a slightly
three-dimensional duct flow but are sufficiently detailed to be used as inlet conditions.
- Velocity vectors: (files mu1@@@.dat) V/Uo, W/Uo
- Contour maps of: (files mu1@@@.dat)
- First order moment U/Uo
- Second order moments
- Reynolds stresses:
- Turbulent kinetic energy: k/Uo2(deduced)
- Wall friction coefficient,Cf, distribution on each wall
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