[marinkobezu]

Hello, I am trying to calculate acoustics of the wing. In Fluent there is FFowcs William Hawkins method and it requires source surface. This surface should enclose all the sound sources and cannot be placed directly on the wing surface. I have created 4 blocks in Pointwise and set up boundary condition as interior between these blocks for the FWH surfaces.(3 circles on the picture). However, in Fluent these Boundary conditions do not show up as sources for FWH method(see second picture). Which boundary condition to use to create FWH surface at some distance from the body?

grid: fig1:http://www.fileconvoy.com/dfl.php?id...697d21651732b6

grid: fig2:http://www.fileconvoy.com/dfl.php?id...af0cc057887905

P.S.According to Fluent User Manual: ( http://www.afs.enea.it/project/neptu...ug/node659.htm )
"Under Source Zones, you can select multiple emission (source) surfaces and the surface Type that you can select is not limited to a wall. You can also choose interior surfaces and sliding interfaces (both stationary and rotating) as source surfaces.
The ability to choose multiple source surfaces is useful for investigating the contributions from individual source surfaces. The results based on the use of multiple source surfaces are valid as long as there are negligible acoustic interactions among the surfaces. Thus, some caution needs to be taken when selecting multiple source surfaces.
In cases where multiple source surfaces are selected, no source surface may enclose any of the other source surfaces. Otherwise, the sound pressure calculated based on the source surfaces will not be accurate, as the contribution from the enclosed (inner) source surfaces is over predicted, since the FW-H model is unable to account for the shading of the sound from the inner source surfaces by the enclosure surface.
If you specify any interior surfaces as source surfaces, the interior surface must be generated in advance (e.g., in GAMBIT) in such a way that the two cell zones adjacent to the surface have different cell zone IDs. Furthermore, you must correctly specify which of the two zones is occupied by the quadrupole sources (interior cell zone). This will allow ANSYS FLUENT to determine the direction in which the sound will propagate. When you first attempt to select a legitimate interior surface (i.e., an interior surface having two different cell zones on both sides) as a source surface, the Interior Cell Zone Selection dialog box (Figure 22.2.5) will appear. You will then need to select the interior cell zones from the two zones listed under the Interior Cell Zone. Figure 22.2.6 shows an example of an interior source surface."

[alireza94]

Originally Posted by marinkobezu

Hello, I am trying to calculate acoustics of the wing. In Fluent there is FFowcs William Hawkins method and it requires source surface. This surface should enclose all the sound sources and cannot be placed directly on the wing surface. I have created 4 blocks in Pointwise and set up boundary condition as interior between these blocks for the FWH surfaces.(3 circles on the picture). However, in Fluent these Boundary conditions do not show up as sources for FWH method(see second picture). Which boundary condition to use to create FWH surface at some distance from the body?

grid: fig1:http://www.fileconvoy.com/dfl.php?id...697d21651732b6

grid: fig2:http://www.fileconvoy.com/dfl.php?id...af0cc057887905

P.S.According to Fluent User Manual: ( http://www.afs.enea.it/project/neptu...ug/node659.htm )
"Under Source Zones, you can select multiple emission (source) surfaces and the surface Type that you can select is not limited to a wall. You can also choose interior surfaces and sliding interfaces (both stationary and rotating) as source surfaces.
The ability to choose multiple source surfaces is useful for investigating the contributions from individual source surfaces. The results based on the use of multiple source surfaces are valid as long as there are negligible acoustic interactions among the surfaces. Thus, some caution needs to be taken when selecting multiple source surfaces.
In cases where multiple source surfaces are selected, no source surface may enclose any of the other source surfaces. Otherwise, the sound pressure calculated based on the source surfaces will not be accurate, as the contribution from the enclosed (inner) source surfaces is over predicted, since the FW-H model is unable to account for the shading of the sound from the inner source surfaces by the enclosure surface.
If you specify any interior surfaces as source surfaces, the interior surface must be generated in advance (e.g., in GAMBIT) in such a way that the two cell zones adjacent to the surface have different cell zone IDs. Furthermore, you must correctly specify which of the two zones is occupied by the quadrupole sources (interior cell zone). This will allow ANSYS FLUENT to determine the direction in which the sound will propagate. When you first attempt to select a legitimate interior surface (i.e., an interior surface having two different cell zones on both sides) as a source surface, the Interior Cell Zone Selection dialog box (Figure 22.2.5) will appear. You will then need to select the interior cell zones from the two zones listed under the Interior Cell Zone. Figure 22.2.6 shows an example of an interior source surface."

Hi marinkobezu

did you find any solution for your problem?

[marinkobezu]

Hello, yes I did. If i remember correctly, domain has to be subdivided to different volume conditions, at that time i had 1 volume condition everywhere.

[alireza94]

Thanks for you replay

[deenriqu]

I had a similar problem: Acoustics of a Jet into a Quiescent fluid.

I generated a 2D mesh in Pointwise. Before exporting mesh you have to cut your domain where you want your interior surface. When assigning boundary conditions, enable "select connectors" and assign the connectors that define your interior surface to the boundary type "interior". Then set 2 different volume zones in the "Volume Conditions" tab. You may have to "orient" your domains if you get exporting errors.



In FLUENT acoustics panel, your connectors should now be selectable as a source zone.

[f14]

i can't define interior source surface in the define source acustic ffowcs
my ansys 18.2
i study ansys help but i can't find the interior cell zone selection dialog box

[deenriqu]

You have to define the interior surface in during the meshing step. Where are you meshing?


Also, I am unable to get Fluent to converge if I use an interior surface. I get a SIGSEV error. Has anyone found a solution?

[marinkobezu]

Hello, you have to select 2 connectors with normals inside and outside. If you select just 1 it will give you an error. You can write me to email marinkobezu@mail.ru