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Shock wave smearing by wall perforation

Doerffer P., Szulc O.

Archives of Mechanics

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2006

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Vol. 58, nr 6

543-573

EN

Normal shock wave, terminating a local supersonic area on an airfoil, not only limits aerodynamic performance but also becomes a significant source of a high-speed impulsive noise on the rotor blade of a helicopter. It is proposed to apply passive control to disintegrate the shock wave by smearing pressure gradients created by the shock. Details of the flow structure obtained by this method are studied numerically. A new boundary condition of a perforated wall is verified against experimental data for a passive control of the shock wave in a channel flow and on an airfoil. This method of shock wave disintegration is proven to work for internal flows in transonic nozzles and appears to be effective for transonic airfoils as well. The substitution of a shock wave by a gradual compression changes completely the source of the high-speed impulsive noise and bears potential of its reduction.

2

Measurement of the air density gradient in transonic flows by the schlieren - speckle photography technique

Szwaba R.

Turbulence : international journal

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2005

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Vol. 11

45-53

EN

This paper presents the description of two non-intrusive optical measurement techniques, which based on refraction and deflection of light rays. These techniques are the Schlieren method and the speckle photography. Especially the latter one have been gain an interesting recently due to dynamic development of computer techniques and digital photography. One of the important parameters in speckle photography is the resolution of the CCD chip of the camera and available resolution reach 16 mln pixels nowadays. Using tliis measurement technique we can obtain the quantitative information of density gradient in the flow with the high spatial resolution. This feature cause that this measurement technique can be use for investigation in turbulent flow.

3

Application of the pressure sensitive paint method for transonic flow measurements

Szumski J. A., Doerffer P.

Turbulence : international journal

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2005

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Vol. 11

55-63

EN

Traditional measurements of the pressure distribution are conducted with use of pressure taps. Those pressure taps require model surface to be drilled through. In case of such intrusive pressure measurements the instrumentation and model mounting become a problem, especially in case of rotating compressor or turbine blades. The new optical method based on pressure (oxygen concentration) sensitive paints allow to obtain a continuous pressure distribution on the model surface in essentially non-intrusive way. The PSP technology helps understanding of the flow around the model and provides quantitative flow data for further processing. PSP method treated in this paper proved to be a very good solution for complex flows. The scope of this paper is to present the basics of the PSP method. It covers only the basic equations, general idea of the method, typical system set up and some of the approaches to PSP paint application. Typical PSP system is explained as well as the formulation of the PSP paint. The physical phenomena of the excitation, emission and oxygen quenching is explained. Deployment of the system at IFFM PAS is in the final stage, and preliminary calibration results are available. At the end of this paper the IFFM PAS plans for future, current PSP development challenges, actions to be taken, and some of the expected results are discussed.