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Passive Control of Shock Wave Applied to Helicopter Rotor High-Speed Impulsive Noise Reduction

100%

Doerffer P. , Szulc O.

2010

tom Vol. 14, No 3

297-305

A strong, normal shock wave, terminating a local supersonic area on an airfoil (or a helicopter blade), not only limits the aerodynamic performance, but also becomes a source of High-Speed Impulsive (HSI) noise. The application of a passive control system (a cavity covered by a perforated plate) on a rotor blade should reduce the noise created by the moving shock. This article describes numerical investigations focused on the application of a passive control device on a helicopter blade in high-speed transonic hover conditions to weaken the shock wave – the main source of HSI noise.

Minimalizacja drgań fundamentu z maszyną

75%

Gołębiowska I. , Sakiewicz W.

2006

tom Nr 3 sp.

30-31

Some methods of construction protection against vibrations are described in the paper. Research results dealing with the efficiency of a multilevel multi-tuned mass damper applied to minimize foundation vibrations with the machine on vibration insulation are presented. It was found that the efficiency of analysed tuned mass damper depended significantly on the mass distribution coefficient in respective levels.

Shock wave smearing by wall perforation

75%

Doerffer P. , Szulc O.

2006

tom Vol. 58, nr 6

543-573

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.