Noise Produced by a Small-scale, Externally Blown Flap PDF Download
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Author: William A. Olsen Publisher: ISBN: Category : Aerodynamics Languages : en Pages : 44
Book Description
Noise data were obtained with a model of an externally blown flap of the type that is currently being considered for STOL aircraft. The noise caused by impingement of the jet on the flap is much louder than the nozzle jet noise. It is especially so directly below the wing. The noise level increases as the jet velocity and flap angle are increased. The sound power level increased with the sixth power of velocity. Several physical variations to the STOL model configuration were also tested. Two such variations, a large board and a slotless curved plate wing, had the same power spectra density (Strouhal number curve) as the model.
Author: William A. Olsen Publisher: ISBN: Category : Aerodynamics Languages : en Pages : 44
Book Description
Noise data were obtained with a model of an externally blown flap of the type that is currently being considered for STOL aircraft. The noise caused by impingement of the jet on the flap is much louder than the nozzle jet noise. It is especially so directly below the wing. The noise level increases as the jet velocity and flap angle are increased. The sound power level increased with the sixth power of velocity. Several physical variations to the STOL model configuration were also tested. Two such variations, a large board and a slotless curved plate wing, had the same power spectra density (Strouhal number curve) as the model.
Author: Martin Haas (S.M.) Publisher: ISBN: Category : Aerodynamic noise Languages : en Pages : 91
Book Description
This report is concerned with the noise generated by blown flaps of the type currently being developed for the short take off and landing aircraft. The majority of the report is an experimental study of the sound-radiation produced by a small scale externally blown double-slotted flap model. Tests were carried out with and without a forward velocity of 60 MPH for a basic engine-wing configuration and for a modified (Engine moved inboard) configuration. Noise radiation patterns and sound pressure level spectra were obtained for nozzle exhaust velocities between 100 and 500 ft/sec. In addition all model data was extrapolated to five fictional full scale STOL aircrafts. The noise generated by the impingement of the jet on the externally blown flap is highly dependent on the jet velocity and the flap position. As the flap angle is increased the noise generated increases. At the 45* - 70* flap position the noise is more than 25db over that caused by the model jet alone. It is especially louder below the wing. The sound power level generated by the externally blown flap (at all positions) increased with the sixth power of the jet's blowing velocity. As the nozzle jet velocity is increased, the sound power level of the noise from the nozzle alone generally increased with the expected eighth power of the jet velocity. Therefore, the difference between the impingement noise and the noise of the nozzle alone decreased with increasing velocity. The noise radiation pattern becomes more directed below the wing as the flaps are lowered. The effect of forward velocity on the noise generated was neglible for a ratio of jet to forward velocity greater than 4.5. Results on tests made on the modified engine-wing configurations were similar to that of the basic configuration except for a slight reduction in overall sound pressure level (2 to 4 db) over all positions measured. An extrapolation to full scale indicated that the externally blown flap noise must be suppressed to meet STOL aircraft noise goals.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781724227584 Category : Languages : en Pages : 32
Book Description
Small scale model acoustic experiments were conducted to measure the noise produced in the flyover and sideline planes by an engine under the wing externally blown flap configuration in its approach attitude. Broadband low frequency noise reductions as large as 9 dB were produced by reducing the separation distance between the nozzle exhaust plane and the flaps. Experiments were also conducted to determine the noise suppression effectiveness in comparison with a reference configuration of three passive types of devices that were located on the jet impingement surfaces of the reference configuration. These devices produced noise reductions that varied up to 10 dB at reduced separation distances. In addition, a qualitative estimate of the noise suppression characteristics of the separate devices was made. Finally static aerodynamic performance data were obtained to evaluate the penalties incurred by these suppression devices. The test results suggest that further parametric studies are required in order to understand more fully the noise mechanisms that are affected by the suppression devices used. Mckinzie, D. J., Jr. Glenn Research Center NASA-TP-1995, E-573, NAS 1.60:1995 RTOP 505-32-2
Author: William A. Olsen
Author: William A. Olsen
Author: William A. Olsen
Author: Martin Haas (S.M.)
Author: National Aeronautics and Space Administration (NASA)
Author: Jack H. Goodykoontz
Author: Jack H. Goodyknoontz
Author: Martin R. Fink
Author: A. P. Pennock
Author: 
Author: