Baughn et al[1] performed flow measurements in a sudden expansion between two circular tubes. The upstream tube was insulated while the downstream one was kept at a uniform wall temperature. The figure below shows the geometry and main flow features, in particular the recirculation region downstream of the expansion. The other figure shows comparisons of predictions with experimental data of wall heat transfer. The cubic k-e model slightly overpredicts it, whereas the dual-dissipation k-e-R closure[2] captures it very well in spite of the difficulty commonly encountered in heat-transfer prediction in reversed flow regions.

[1] Baughn, J.W., Hoffman, M.A., Launder, B.E., Lee D. and Yap, C., `Heat-Transfer, Temperature, and Velocity Measurements Downstream of an Abrupt Expansion in a Circular Tube at a Uniform Wall Temperature', ASME Journal of Heat-Transfer, Vol. 111, November 1989, pp. 870-876.
[2] Goldberg, U. and Batten, P., `Heat-Transfer Predictions using a Dual-Dissipation k-e Turbulence Closure', submitted to AIAA J. Thermophys. & Heat-Transfer. Also to be presented in the AIAA 39th Aerospace Sciences Meeting, Reno, NV, Jan. 2001.