INDUCED FLUCTUATIONS OF AIR FLOW IN A DUCT WITH TOOTHED WALLS

Abstract

Experimental and numerical studies have focused interest in the flow field with toothed walls surfaces and cavities, where the flow turbulence is captured in images with the Schlieren technique and recreated with computer codes. In the present work, a numerical study is carried out for the air flow in a straight duct with serrated walls for six pressure cases. The flow was simulated for a 2D computational domain with the ANSYS-Fluent code, for which the RANS model was used in conjunction with the Menter turbulence model. The fields of Mach number, velocity, pressure and temperature with the presence of eddies and shock waves were obtained. In certain regions the flow presented deviations when it collided with the corners of the teeth, for which it originated induced fluctuations of the thermodynamic parameters downstream and towards the central region; swirls were present in the spaces between teeth; oblique shock waves were present at the end of the last tooth. It is concluded that the toothed section increases turbulence and influences the flow velocity to have a stepped increase in the transonic regime.

Keywords: duct, air flow, fluctuation, shock wave, toothed wall, simulation.

References

[1]J. Blazek, Computational fluid dynamics: principles and applications. Butterworth- Heinemann, 2015.

[2]B. Andersson, R. Andersson, L. Håkansson, M. Mortensen, R. Sudiyo, B. van Wachem, and L. Hellström, Computational Fluid Dynamics Engineers. Cambridge University Press, 2012.

[3]T. V. Karman, “The fundamentals of the statistical theory of turbulence,” Journal of the Aeronautical Sciences, vol. 4, no. 4, pp. 131–138, 1937. doi: 10.2514/8.350.

[4]F. White, Viscous fluid flow. McGraw-Hill Education, 2005.

[5]H. Schlichting, Boundary-layer theory. McGraw-Hill classic textbook reissue series, 2016.

[6]J. D. Anderson, Fundamentals of aerodynamics. McGraw-Hill series in aeronautical and aerospace engineering, 2017.

[7]D. C. Wilcox, Turbulence modeling for CFD. DCW Industries, 2006.

[8]P. Krehl and S. Engemann, “August toepler — the first who visualized shock waves,” Shock Waves, vol. 5, no. 1, pp. 1–18, Jun 1995. doi: 10.1007/BF02425031.

[9]G. S. Settles, “Toma ultrarrápida de imágenes de ondas de choque, explosiones y disparos,” Revista Investigación y Ciencia, pp. 74-83, May. 2006. https://www.investigacionyciencia.es

[10]H. Hirahara, M. Kawahashi, M. U, Khan and K. Hourigan, “Experimental investigation of fluid dynamic instability in a transonic cavity flow,” Experimental Thermal and Fluid Science, 31, pp. 333–347, 2007. doi: 10.1016/j.expthermflusci.2006.05.007.

[11]S. L. Tolentino, S. Caraballo, J. Toledo, J. Mírez and C. Torres, “Oscilaciones de la velocidad del flujo en un ducto recto con cavidades rectangulares,” XVI Jornadas de Investigación 2018, UNEXPO Puerto Ordaz, Venezuela, pp. 34-39, 2018.

[12]S. Jeyakumar, K. A. Yuvaraj, K. Jayaraman, F. Cardona and M. T. Sultan, “Effect of cavity fore wall modifications in supersonic flow,” Conference, Materials Science and Engineering, 152, pp. 1-7, 2016. doi: 10.1088/1757-899X/152/1/012002.

[13]S. L. Tolentino and S. Caraballo, “Estudio del flujo de aire en un conducto recto con pared dentada,” XIV Jornadas de Investigación 2016, UNEXPO Puerto Ordaz, Venezuela, pp. 203-210, 2016.

[14]F. White, Fluids Mechanics. McGraw-Hill Education, 2016.

[15]F. R. Menter, “Two equation eddy-viscosity turbulence models for engineering applications,” AIAA Journal, vol. 32, no. 8, pp. 1598-1605, 1994. doi: 10.2514/3.12149.

[16]S. L. B. Tolentino Masgo, “Evaluación de modelos de turbulencia para el flujo de aire en una tobera plana,” Revista Ingenius, no. 22, pp. 25-37, Julio-Diciembre 2019. doi: 10.17163/ings.n22.2019.03.

[17]S. L. B. Tolentino Masgo, “Evaluación de modelos de turbulencia para el flujo de aire en un difusor transónico,” Revista Politécnica, vol. 45, no. 1, pp. 25-38, 2020. doi: 10.3333/rp.vol45n1.03.