======Square-Section Duct 180 Degree Bend======
=====Experiments by Choi, Moon, Yang=====

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====Description====

Turbulent flow in a square cross-section duct made of a 180<sup>o</sup> bend and two
long straight inlet and outlet parts. 3D flow with constant temperature.

===Geometry of the Computational Domain===

180<sup>o</sup> bend section connected to straight inlet and outlet tangents, all
of square section: \(D \times D = 88.9 \times 88.9\) mm.
Centreline curvature radius of the bend: \(R_c = 3.357D\) (see <imgref cas6-geom>).

In the experiment the inlet section consisted of a straight duct of around \(30D\) length,
with the flow reported to be close to fully developed on approaching the bend section.

<imgcaption cas6-geom| Duct bend geometry and coordinate system>{{  figs:case006:choi-geom2.png | Duct bend geometry}}</imgcaption>

===Flow Parameters===

Air at standard conditions.

  * Inlet bulk axial velocity \(W_B = 11\) m/s.
  * Reynolds number based on the bulk axial velocity \(W_B\): \(Re = W_B D/\nu = 56,690\).

===Inflow Conditions===

Measurements/simulation data corresponding to a fully-developed turbulent duct flow are
provided in file {{cdata:case006:inlet-data.dat|inlet-data.dat}}, consisting of contour maps of:

  * First order moments: \(U\), \(V\), \(W\)
  * Turbulent kinetic energy, \(k\) and dissipation rate, \(\varepsilon\)

If using these it is suggested to apply them at least \(1D\) upstream of the bend inlet.

====Experimental Details====

Velocity measurements using a rotatable hot-wire probe.

===Measurement Errors===

Analyzed but no published values.

====Available Measurements====

Contour maps are provided at 5 different angular positions (\(\Psi = 0^o\), \(45^o\), \(90^o\), \(135^o\), \(180^o\)) of:

  * First order moments: \(U/W_B\), \(V/W_B\), \(W/W_B\)
  * Second order moments: \(u'/W_B\), \(v'/W_B\), \(w'/W_B\), \(\overline{uv}/W_B^2\), \(\overline{uw}/W_B^2\), \(\overline{vw}/W_B^2\)

[[case006-plots|Sample plots]] of selected quantities are available.

The data can be downloaded as compressed archive files from the links
below, or as individual files by selecting those required from the
tables.

  * {{cdata:case006:sqd-allfiles.zip|sqd-allfiles.zip}}
  * {{cdata:case006:sqd-allfiles.tar.gz|sqd-allfiles.tar.gz}}

^    ^  Mean velocities file   ^  Second Moments  ^
| \(\Psi=0^o\) |  {{cdata:case006:sqd-vel-000.dat|sqd-vel-000.dat}}  |  {{cdata:case006:sqd-rss-000.dat|sqd-rss-000.dat}}  |
| \(\Psi=45^o\) |  {{cdata:case006:sqd-vel-045.dat|sqd-vel-045.dat}}  |  {{cdata:case006:sqd-rss-045.dat|sqd-rss-045.dat}}  |
| \(\Psi=90^o\) |  {{cdata:case006:sqd-vel-090.dat|sqd-vel-090.dat}}  |  {{cdata:case006:sqd-rss-090.dat|sqd-rss-090.dat}}  |
| \(\Psi=135^o\) |  {{cdata:case006:sqd-vel-135.dat|sqd-vel-135.dat}}  |  {{cdata:case006:sqd-rss-135.dat|sqd-rss-135.dat}}  |
| \(\Psi=180^o\) |  {{cdata:case006:sqd-vel-180.dat|sqd-vel-180.dat}}  |  {{cdata:case006:sqd-rss-180.dat|sqd-rss-180.dat}}  |

====Main References====

  - Choi, Y.D., Moon C., Yang, S.H. (1990). Measurement of turbulent flow characteristics of square duct with a 180 degree bend by hot wire anemometer. //Proc. Int. Symp. on Engineering Turbulence Modelling and Measurement//, Dubrovnik.
  - Chang, S.M., Humphrey, J.A.C., Modavi, A. (1983). Turbulent flow in a strongly curved U-bend and downstrean tangent of square cross sections. //Physico-Chemical Hydrodynamics//, Vol. 4, pp. 243-269.
  - Choi, Y.D., Iacovides, H., Launder, B.E. (1989). [[https://doi.org/10.1115/1.3243600|Numerical computation of turbulent flow in a square-sectioned 180 deg bend]]. //J. Fluids Engg.// Vol. 111, pp. 59-68.
  - Sotiropoulos, F., Patel, V.C. (1993). Evaluation of some near-wall models for the Reynolds-stress transport equations in a complex 3-D shear flow. //Near wall turbulent flows// (eds. R.M.C. So, C.G. Speziale, B.E. Launder), pp. 987-998.

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Indexed data:
<data dbcase confined_flow>
case       : 006
title      : Square-Sectioned Duct 180 degree Bend
author*    : Choi, Moon, Yang
year       : 1990
type       : EXP
flow_tag*  : 3d, curvature, constant_cross_section
</data>