ABSTRACT Numerical results of three-dimensional separated flow and heat transfer in an enlarged rectangular channel are presented in this paper. The expansion ratio and aspect ratio of the channel are 2.0 and 8.0, respectively. Reynolds number of the flow is 200 and it is over the critical Reynolds number. Over the value, the flow in the symmetric channel becomes to deflect to one side of the walls. Transient response characteristics of the flow and heat transfer in the channel with the fully developed flow imposed one cycle of a pulsating fluctuation at the inlet are investigated. Vortex structure generated in the channel is visualized with a helicity isosurface. In the case of the fluctuation of Strouhal number 0.05, small streamwise vortices appear near the side walls and slightly upstream of the reattachment region of the short separation bubble. The vortices elongate and shed some vortices. These vortices attract some pairs of the streamwise vortices near the reattachment region quickly and they drift downstream along the side walls. They are inclined from the walls and are decaying gradually. It is clarified that high Nusselt number area appears and shifts downstream in accordance with the root of the vortices.
Cite this paper
H. Yoshikawa, S. Shirakura and M. Munekata, "Transient Response Characteristics of Separated Flow and Heat Transfer in Enlarged Rectangular Channel," Open Journal of Fluid Dynamics, Vol. 2 No. 4, 2012, pp. 278-284. doi: 10.4236/ojfd.2012.24A033.
 D. E. Abbott and S. J. Kline, “Experimental Investigations of Subsonic Turbulent Flow over Single and Double Backward Facing Steps,” Journal of Basic Engineering, Vol. 84, No. 3, 1962, pp. 317-325.
 T. Ito, Y. Suematsu, Y. Simokawa and K. Tanaka, “A Study on the Bistable Fluid Amplifier Load Oscillator (1st Report, On the Flow Characteristics of the Fluid Amplifier),” Transactions of JSME, Vol. 39, No. 321, 1973, pp. 1599-1608. doi:10.1007/s11630-011-0437-x
 W. Cherdron, F. Durst and J. H. Whitelaw, “Asymmetric Flows and Instabilities in Symmetric Ducts with Sudden Expansions,” Journal of Fluid Mechanics, Vol. 84, No. 1, 1978, pp. 13-31. doi:10.1017/S0022112078000026
 I. J. Sobey, “Observation of Waves during Oscillatory Channel Flow,” Journal of Fluid Mechanics, Vol. 151, 1985, pp. 395-426. doi:10.1017/S0022112085001021
 A. Nishihara, K. Suzuki and Y. Inoue, “Numerical Analysis of Flow and Heat Transfer in an Enlarged Channel,” Proceedings of 26th National Heat Transfer Symposium of Japan, Vol. 1, Sendai, 31 May-2 June 1989, pp. 37-39.
 M. Shapira, D. Degani and D. Weihs, “Stability and Existence of Multiple Solutions for Viscous Flow in Suddenly Enlarged Channels,” Computers & Fluids, Vol. 18, No. 3, 1990, pp. 239-258.
 R. M. Fearn, T. Mullin and K. A. Cliffe, “Nonlinear Flow Phenomena in a Symmetric Sudden Expansion,” Journal of Fluid Mechanics, Vol. 211, 1990, pp. 595-608.
 T. Ota and Y. Toda, “Prediction of Laminar Heat Transfer and Flow in Plane Enlarged Channels (Heat Transfer 1990),” Hemisphere Publishing Corporation, New York, 1990, pp. 305-309.
 F. Durst, J. C. F. Pereira and C. Tropea, “The Plane Symmetric Sudden Expansion Flow at Low Reynolds Numbers,” Journal of Fluid Mechanics, Vol. 248, 1993, pp. 567-581. doi:10.1017/S0022112093000916
 T. Ota, H. Yanaoka and T. Hata, “Numerical Analysis of Laminar Flow and Heat Transfer in a Two-Dimensional Symmetrically Enlarged Channel,” Transactions of JSME, Vol. 60B, No. 579, 1994, pp. 3930-3936.
 S. Nakanishi, M. Sakurai and H. Osaka, “Numerical Study on Two-Dimensional Symmetric Sudden Expansion Channel Flow (Dynamic Characteristics),” Transactions of JSME, Vol. 61B, No. 589, 1995, pp. 3182-3189.
 D. Drikakis, “Bifurcation Phenomena in Incompressible Sudden Expansion Flows,” Physics of Fluids, Vol. 9, No. 1, 1997, pp. 76-87. doi:10.1063/1.869174
 E. Schreck and M. Sch?fer, “Numerical Study of Bifurcation in Three-Dimensional Sudden Channel Expansions,” Computers & Fluids, Vol. 29, No. 5, 2000, pp. 583-593.
 M. Thiruvengadam, J. H. Nie and B. F. Armaly, “Bifurcated Three-Dimensional Forced Convection in Plane Symmetric Sudden Expansion,” International Journal of Heat and Mass Transfer, Vol. 48, No. 15, 2005, pp. 31283139. doi:10.1016/j.ijheatmasstransfer.2005.02.019
 H. Yanaoka and T. Ota, “Three-Dimensional Numerical Simulation of Laminar Flow and Heat Transfer over Blunt Flat Plate in a Channel,” Transactions of JSME, Vol. 62B, No. 596, 1996, pp. 1496-1501.
 H. Yanaoka and T. Ota, “Three-Dimensional Numerical Simulation of Unsteady Flow and Heat Transfer over Blunt Flat Plate in Channel,” Transactions of JSME, Vol. 62B, No. 599, 1996, pp. 2745-2750.
 T. Ota, H. Yanaoka, K. Shibuya, M. Nakajima and H. Yoshikawa, “Numerical Simulation of Separated Flow and Heat Transfer in a Rectangular Channel with Sudden Expansion,” Proceedings of ASME FEDSM, Boston, 11-15 June 2000, Paper No. FEDSM00-11004.
 H. Iwai, K. Nakabe and K. Suzuki, “Flow and Heat Transfer Characteristics of Backward-Facing Step Laminar Flow in a Rectangular Duct,” International Journal of Heat and Mass Transfer, Vol. 43, No. 3, 2000, pp. 457471. doi:10.1016/S0017-9310(99)00140-4
 H. Yoshikawa, T. Kai, M. Munekata and H. Ohba, “Effects of Pulsation on Separated Flow and Heat Transfer in Enlarged Channel,” Journal of Thermal Science, Vol. 20, No. 1, 2011, pp. 70-75. doi:10.1007/s11630-011-0437-x
 C. Fan and B. Chao, “Unsteady, Laminar, Incompressible Flow through Rectangular Ducts,” Zeitschrift für angewandte Mathematik und Physik (ZAMP), Vol. 16, No. 3, 1965, pp. 351-360. doi:10.1007/BF01591915
 A. A. Amsden and F. H. Harlow, “A Simplified MAC Technique for Incompressible Fluid Flow Calculations,” Journal of Computational Physics, Vol. 6, No. 2, 1970, pp. 322-325. doi:10.1016/0021-9991(70)90029-X