2004 Fiscal Year Final Research Report Summary
Control and Application of a Locked in Phenomenon of a Jet Screech/Self-Exited-Vibration by using a Spherical Reflector.
| Project/Area Number |
15560201
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Dynamics/Control
|
|---|
| Research Institution | SAGA UNIVERSITY |
|---|
Principal Investigator |
SETO Kunisato Saga University, Mechanical Engineering, Professor, 理工学部, 教授 (80039271)
|
|---|
| Project Period (FY) |
2003 – 2004
|
| Keywords | Spherical Reflector / Jet Screech / Shock Wave / Self-Exited Vibration / Resonance / Noise Cancellation / Sound Shielding |
|---|
| Research Abstract |
One of the purposes of the present research is to clarify the generation mechanism of jet screech. The special issues are interaction between vortex disturbances and a shock wave and a resonance mechanism caused through instability of shear layer near to the exit of a nozzle.
The next one is to control the jet screech by using a spherical reflector set at the nozzle exit that controls the location of an image noise source and cancels the jet screech.
(1)In order to identify the coherence of sound waves, a laser beam sound detector has been designed and built up. Fundamental data of the performance have been obtained through current investigations.
(2)Visual observation of the change in flow field by the attachment of a spherical reflector has been carried out by using a Schlieren system and a high speed video camera. It was found that the shock cell structure was kept up to downstream in case of the attachment of the spherical reflector. The reason is that cancellation of sound waves at t
… More
he nozzle exit quits exciting instability and stops generating disturbances. Hence the interaction between the disturbances and a shock wave becomes weak and the structure of the shock wave is not hampered.
(3)The above mentioned observation has been carried out through a spherical reflector with a slit hole. The slit hole lowered the level of the noise cancellation but still held the effect.
(4)Comparison of the sound cancellation effect between a spherical reflector and a flat plane reflector has been carried out.
(5)Comparison of the sound cancellation effect between a spherical reflector and a parabola reflector has been carried out.
(6)Sizing effect of a spherical reflector has been investigated by a variety of reflectors. It was confirmed that even a small sized spherical reflector could cancel a jet screech.
(7)Noise reducing effect of spherical reflectors has been studied at various pressure ratios and it was shown that there is an appropriate radius of curvature corresponding to each pressure ratio.
(8)In the above experiment, it was found that there was a special pressure ratio corresponding to any size of a spherical reflector where the noise reducing effect was highest.
(9)Preparation for the measurement of magnitude of resistance (thrust loss) of a spherical reflector in flow has been done.
(10)Preparation for the application of a spherical reflector to a duct silencer has been done. Less
|
