Abstract    In the current study, twin wind blades are designed, fabricated and the effect of various gap ratio (g*) at various angle of attacks (α) on a next to each other twin wind blades are examined in an open-channel wind tunnel. Aerodynamic forces and moments are determined by using three-constraint force balancer. For gap ratio of zero, the aerodynamic attributes are like those of a solitary wind blade edge. As g* increases, these two wind blades actuate the vertical wake to stage vortex shedding modes. With further increment in g*, the wake stream pattern was like those behind a solitary wind blade. For a solitary wind blade, the maximum lift is found to be at α = 30. The pitching moment increases with α. The impact of upper aerofoil blade on the lower one diminished as g* increases.

Keywords    Rotor, Flow characterization, Aerodynamic Performance, CFD Investigation

چکیده    در مطالعه حاضر، تیغه های دوقلو بادی طراحی و ساخته شده اند و اثر نسبت فاصله گشتاور (g *) در زاویه های مختلف حملات (α) در کنار یکدیگر تیغه های دوقلوی باد در یک تونل باد باز کانونی بررسی می شود. نیروها و ممانت آیرودینامیکی با استفاده از سه برابر کننده تعادل نیروی محدود تعیین می شود. برای نسبت شکاف صفر، مشخصه های آیرودینامیک مانند لبه ی تیغه ی انفرادی است. همانطور که g * افزایش می یابد، این دو تیغه باله به سمت عمودی حرکت می کنند تا حالت های انفجار گردابه را کنترل کنند. با افزایش بیشتر در g *، الگوی جریان پی در پی همانند کسانی بود که پشت یک تیغه ی هوای انفرادی بودند. برای یک تیغه ی هوای انفرادی، حداکثر لیفت در α = 30 دیده می شود. لحظه ی پچینگ با α افزایش می یابد. تاثیر تیپ بالایی هواپیما بر روی پایین تر به عنوان g * افزایش می یابد.

References    1.     Batill, S.M. and Mueller, T.J., "Visualization of transition in the flow over an airfoil using the smoke-wire technique", American Institute of Aeronautics and Astronautics Journal,  Vol. 19, No. 3, (1981), 340-345. 2.     Lissaman, P., "Low-reynolds-number airfoils", Annual Review of Fluid Mechanics,  Vol. 15, No. 1, (1983), 223-239. 3.     Goldstein, R., Flow visualization by direct injection, in Fluid mechanics measurements, second edition. 2017, Routledge.391-474. 4.     Crabtree, L., "Effects of leading-edge separation on thin wings in two-dimensional incompressible flow", Journal of the Aeronautical Sciences,  Vol. 24, No. 8, (1957), 597-604. 5.     Dong, G.-J. and Lu, X.-Y., "Characteristics of flow over traveling wavy foils in a side-by-side arrangement", Physics of Fluids,  Vol. 19, No. 5, (2007), 057107. 6.     Hansen, M.O. and Madsen, H.A., "Review paper on wind turbine aerodynamics", Journal of Fluids Engineering,  Vol. 133, No. 11, (2011). 7.     Sieverding, C.H., Richard, H. and Desse, J.-M., "Turbine blade trailing edge flow characteristics at high subsonic outlet mach number", Journal of Turbomachinery,  Vol. 125, No. 2, (2003), 298-309. 8.     Saranprabhu, M., Tirumalaisamudram, T., Kumar, B.R. and Sreehari, V., "Aero-thermodynamic analysis of a supersonic aircraft",  Journal of advanced research and dynamical control special issue 11, (2017),120-127. 9.     Abbishek, R., Kumar, B.R. and Subramanian, H.S., "Fatigue analysis and design optimization of aircraft’s central fuselage", in IOP Conference Series: Materials Science and Engineering, IOP Publishing. Vol. 225, (2017), 012031. 10.   Ashory, M., Talebi, F. and Ghadikolaei, H.R., "A computational study about the effect of turbines pitched blade attack angle on the power consumption of a stirred tank", International Journal of Engineering-Transactions A: Basics,  Vol. 31, No. 1, (2017), 65-70. 11.   Rajabi, N., Rafee, R. and Frazam-Alipour, S., "Effect of blade design parameters on air flow through an axial fan", International Journal of Engineering-Transactions A: Basics,  Vol. 30, No. 10, (2017), 1583. 12.   Uzol, O., Chow, Y.-C., Katz, J. and Meneveau, C., "Experimental investigation of unsteady flow field within a two stage axial turbomachine using particle image velocimetry", in ASME Turbo Expo 2002: Power for Land, Sea, and Air, American Society of Mechanical Engineers., (2002), 1201-1214. 13.   Yen, S.C. and Liu, J.H., "Wake flow behind two side-by-side square cylinders", International Journal of Heat and Fluid Flow,  Vol. 32, No. 1, (2011), 41-51. 14.   Nejad, A.Z., Rad, M. and Khayat, M., "Numerical and experimental investigations for design of a high performance micro-hydro-kinetic turbine", International Journal of Engineering-Transactions B: Applications,  Vol. 30, No. 5, (2017), 785. 15.   Amanifard, N., "Stall vortex shedding over a compressor cascade (research note)", International Journal of Engineering-Transactions A: Basics,  Vol. 18, No. 1, (2004), 29-36.