Author: Krishan K. AhujaPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Blown Flap Noise Test
Author: Krishan K. AhujaStatic and Wind Tunnel Model Tests for the Development of Externally Blown Flap Noise Reduction Techniques
Author: A. P. PennockPublisher:
ISBN:
Category : Aerodynamic noise
Languages : en
Pages : 336
Book Description
Noise Tests on an Externally Blown Flap with the Engine in Front of the Wing
Author: Allen M. KarchmerPublisher:
ISBN:
Category : Jet engines
Languages : en
Pages : 14
Book Description
Externally-blown-flap Noise
Author: Blown Flap Noise
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.
Mixer Nozzle-externally Blown Flap Noise Tests
Author: Noise Tests of a Mixer Nozzle-externally Blown Flap System
Author: Jack H. GoodykoontzPublisher:
ISBN:
Category : Flaps (Airplanes)
Languages : en
Pages : 60
Book Description
Noise tests were conducted on a large scale model of an externally blown flap lift augmentation system, employing a mixer nozzle. The mixer nozzle consisted of seven flow passages with a total equivalent diameter of 40 centimeters. With the flaps in the 30 - 60 deg setting, the noise level below the wing was less with the mixer nozzle than when a standard circular nozzle was used. At the 10 - 20 deg flap setting, the noise levels were about the same when either nozzle was used. With retracted flaps, the noise level was higher when the mixer nozzle was used.
Noise Reduction Tests of Large Scale Model Externally Blown Flap Using Trailing-edge Blowing and Partial Flap Slot Covering
Author: Daniel J. McKinziePublisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 70
Book Description
Noise Produced by a Small-scale, Externally Blown Flap
Author: William A. OlsenPublisher:
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: