Wake-Induced Bypass Transition over a Flat Plate under Favorable and Adverse Pressure Gradients

Eitaro Koyabu, Tetsuhiro Tsukiji

Department of Engineering and Applied Sciences, Sophia University, Tokyo, Japan.
Department of Mechanical Engineering, Tomakomai National College of Technology, Tomakomai, Japan.

DOI: 10.4236/jfcmv.2013.11003                

Abstract

The present study investigates wake-induced bypass transition of boundary layers on a flat plate subjected to favorable and adverse pressure gradients. The aim is to exploit unsteady effects in order to design an aft-loaded turbine blade without increasing the profile loss, as has been achieved for low pressure turbine blades. First of all, this fundamental study is to reveal the effect of the Strouhal number, which changed by using different numbers of wake generating bars. Detailed boundary layer measurements were conducted using two hot-wire probes. A passage-contouring device was employed to generate a pressure gradient on the test model, which was typical to that generated by an aft-loaded turbine blade. A spoked-wheel-type wake generator was used to create periodic wakes in front of the flat plate. It was found that the wake passage induces a significant change in the flow structure downstream of the flow acceleration region.

Keywords

Boundary Layer; Wake; Transition; Pressure Gradient; Hot-Wire Anemometry

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	R. E. Mayle, “The Role of Laminar-Turbulent Transition in Gas Turbine Engines,” ASME Journal of Turbomachinery, Vol. 113, No. 4, 1991, pp. 509-537. doi:10.1115/1.2929110
[2]	G. J. Walker, “The Role of Laminar-Turbulent Transition in Gas Turbine Engines: A Discussion,” ASME Journal of Turbomachinery, Vol. 115, No. 2, 1993, pp. 207-217. doi:10.1115/1.2929223
[3]	D. E. Halstead, D. C. Walker, T. H. Okiishi, G. J. Walker, H. P. Hodson and H.-W. Shin, “Boundary Layer Development in Axial Compressors and Turbines: Part 1 of 4-Composite Picture,” ASME Journal of Turbomachinery, Vol. 119, No. 1, 1997, pp. 114-127. doi:10.1115/1.2841000
[4]	D. E. Halstead, D. C. Walker, T. H. Okiishi, G. J. Walker, H. P. Hodson and H.-W. Shin, “Boundary Layer Development in Axial Compressors and Turbines: Part 1 of 3-LP Turbines,” ASME Journal of Turbomachinery, Vol. 119, No. 2, 1997, pp. 225-237. doi:10.1115/1.2841105
[5]	E. Koyabu, K. Funazaki and J. Takahashi, “Boundary Layer Bypass Transition on a Flat Plate Induced by Periodic Wake Passage Affected Pressure Gradients (Effect of Free-Stream Turbulence),” Journal of the Gas Turbine Society of Japan, Vol. 29, No. 625, 2001, pp. 485-492．
[6]	E. Koyabu, K. Funazaki and M. Kimura, “Experimental studies on Wake-Induced Bypass Transition of Flat-Plate Boundary Layers under Favorable and Adverse Pressure Gradients,” JSME International Journal Series B Fluids and Thermal Engineering, Vol. 48, No. 3, 2005, pp. 579-588. doi:10.1299/jsmeb.48.579
[7]	J. D. Coull, R. L. Thomas and H. Hodson, “Velocity Distributions for Low Pressure Turbines,” ASME Journal of Turbomachinery, Vol. 132, No. 4, 2010, pp. 1-12.
[8]	K. Funazaki, N. Tanaka and M. Kikuchi, “Studies on High-Lift LP Turbine Airfoils of Aero Engines,” Transactions of JSME, Series B, Vol. 74, No. 747, 2008, pp. 2301-2310.
[9]	X. Ottavy, S. Vilmin, M. Opoka, H. Hodson and S. Gallimore, “The Effects of Wake-Passing Unsteadiness over a Highly Loaded Compressor-Like Flat Plate,” 2002, ASME Paper GT-2002-30354.
[10]	R. J. Volino and L. S. Hultgren, “Measurements in Separated and Transitional Boundary Layers under Low-Pressure Turbine Airfoil Conditions,” ASME Journal of Turbomachinery, Vol. 123, No. 2, 2000, pp. 189-197.
[11]	S. J. Kline and F. A. McClintock, “Describing Uncertainties in Single-Sample Experiments,” Mechanical Engineering, Vol. 75, No. 1, 1953, pp. 3-8.
[12]	K. Funazaki, Y. Yamashita and S. Yamawaki, “Studies on Unsteady Boundary Layers on a Flat Plate Subjected to Incident Periodic Wakes and Free-Stream Turbulence,” Journal of the Gas Turbine Society of Japan, Vol. 21, No. 81, 1993, pp. 62-69.