Directivity

November 28, 2001, 02:31

Dear all,

in computational aeroacoustics it is often talked about DIRECTIVITY. Can anybody tell me what does it mean and how to compute it?

Thanks in advance Matthias

December 4, 2001, 13:27

Well, for a given distance from your noise source (you somehow have to be far enough to consider that your observer is at the same distance of all the sources in question (if you use a Kirchhoff or FW-H method for example), you describe a certain distribution of observer angles say with respect to the downstream axis. Practical case, I investigate the aerodynamic noise of a landing gear: for each directivity plot, I use 72 observers (one every 5 degrees), at 10 radii, 20 radii, 30 radii, etc... from the center of the landing gear. I give you a link to some plots I made which illustrate the observer grid and the resulting directivity plot. http://cocoa.aero.psu.edu/~fjs121/LDGdebug/directivity/ Viel Glueck (Bonne chance?)

Fred.

November 28, 2001, 02:31	Directivity	#1
Matthias Guest Posts: n/a	Dear all, in computational aeroacoustics it is often talked about DIRECTIVITY. Can anybody tell me what does it mean and how to compute it? Thanks in advance Matthias

December 4, 2001, 13:27	Re: Directivity	#2
Fred Souliez Guest Posts: n/a	Well, for a given distance from your noise source (you somehow have to be far enough to consider that your observer is at the same distance of all the sources in question (if you use a Kirchhoff or FW-H method for example), you describe a certain distribution of observer angles say with respect to the downstream axis. Practical case, I investigate the aerodynamic noise of a landing gear: for each directivity plot, I use 72 observers (one every 5 degrees), at 10 radii, 20 radii, 30 radii, etc... from the center of the landing gear. I give you a link to some plots I made which illustrate the observer grid and the resulting directivity plot. http://cocoa.aero.psu.edu/~fjs121/LDGdebug/directivity/ Viel Glueck (Bonne chance?) Fred.