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Old   July 25, 2000, 10:41
Default Aerofoils/blades with rounded trailing edge.
  #1
Sergei Chernyshenko
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Hi.

NACA aerofoils are sometimes a convenient object since all you need is to say something like NACA6512 to define it uniquely. They have sharp trailing edge, however. Does anyone know any aerofoil (compressor blade) shape family with rounded trailing edge?

Thanks. Sergei
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Old   July 25, 2000, 11:41
Default Re: Aerofoils/blades with rounded trailing edge.
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John C. Chien
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(1). The blade shapes are defined with a leading edge circle and a trailing edge circle. (2). The trailing edge circle can be truncated to give a blunt trailing edge. (2). There is no such thing as a sharp trailing edge blade in design. (you can only find such crude approximation in the Denton and Dawes analysis codes. Very bad codes and approximation)
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Old   July 25, 2000, 11:45
Default Re: Aerofoils/blades with rounded trailing edge.
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Nishikawa
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For some(maybe all) NACA airfoils, trailing edge is in fact not closed. There is a small gap at TE. So you may round the TE (still sharp?), or extend a little bit to form a sharp TE. How to close it is your choice.

For low-Reynolds number flows, there is an experimental work on airfoil with blunt TE, which demonstrates that L/D can be improved by removing the rear half of a conventional airfoil such as NACA. (AIAA Journal 1995 or 1996. I remember that it was on the first page.)

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Old   July 25, 2000, 11:54
Default Re: Aerofoils/blades with rounded trailing edge.
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Sergei Chernyshenko
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Hi, John,

>(1). The blade shapes are defined with a leading edge circle and a trailing edge circle.

Not NACA series. . I asked for a reference to such or similar definitons.

>(2). The trailing edge circle can be truncated to give a blunt trailing edge.

This is what I do. And add lengthy explanations of how exactly it was truncated. These explanations I would like to eleminate by referring to a widely-known something.

>(2). There is no such thing as a sharp trailing edge blade in design.

This I understand . Still, when you look at descriptions of many experiments, they say NACA6512, and nothing more.

Thanks. Sergei
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Old   July 25, 2000, 12:48
Default Re: Aerofoils/blades with rounded trailing edge.
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Sergei Chernyshenko
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Thanks. Sergei.
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Old   July 25, 2000, 19:51
Default Re: Aerofoils/blades with rounded trailing edge.
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John C. Chien
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(1). PP. 74~78, section 2.5.1 Aerodynamic shapes and type of blading used, axial compressors and fans, Book by B. Lakshminarayana, " 1996, John Wiley and Sons,Inc," fluid dynamics and heat transfer of turbomachinery" (2). Hobbs, weingold, 1984, J.eng. for gas turbines an power, vol.106,p271, "development of controlled diffusion airfoils for multi-stage compressor applications".
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Old   July 26, 2000, 05:10
Default Re: Aerofoils/blades with rounded trailing edge.
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Sergei Chernyshenko
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Thank you very much. Sergei.
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