耦合声学有限元计算

mxlzhenzhu

时间紧迫，我要增加悬赏

现在有点进步了；但是还是有点疑问：
1、耦合分析的边界条件问题
书上这样说的：
对于流体外部边界可以分为四种情况
        A、直接施加的声压
        B、直接施加的法向振动速度
        C、施加法向表面阻抗边界条件
        D、速度连续边界条件
其中，D就是流固耦合的振动速度连续条件；

而在Vibro-Acoustic Analysis Case  帮助文档里面，需要定义6项：1=边界条件，而且施加到声学模型上；2，Load Function Set，添加的类型必须是“力”，而且只能施加到结构模型上；3，Load Vector Set，只能是声压数据，而且只能施加到结构模型上；4、声模态；5、结构模态；6、湿表面。原文如下：


Vibro-Acoustic Analysis Case

1 Boundary Condition Set
You can either impose or not impose the boundary condition for the Vibro-Acoustic Response Analysis Case.
Boundary conditions must be applied to the acoustic model. If you do not want to impose the boundary condition,
select the No Boundary Condition Set option. You can either create a new boundary condition set or reference
an existing one. Select the Create a New Boundary Condition Set option to create a new boundary condition set,
which then needs to be defined. Select the Use an Existing One option, to reference an existing boundary condition
set from the Specification Tree. Selecting this option will activate a feature selection box below it.
Select an Acoustic Boundary Condition and Source feature from the Specification Tree. The selected feature’s
name will appear in this selection box as shown in the image below.

2 Load Function Set
This dialog section controls the specification of a Load Function Set - a collection of 2D excitation functions - as
load definition for the vibro-acoustic analysis. The load function must be of type “Force” and must be applied to
the structural model. If you do not want to include the load function set in the Vibro-Acoustic Response Analysis Case,
select the No Load Function Set option. You can also either create a new load function set or reference an existing one.
Select the Create a New Load Function Set option to create a new load function set, which then needs to be defined.
Select the Use an Existing One option, to reference an existing load function set from the Specification Tree.
Selecting this option will activate a feature selection box below it in order to select the available load function set
from the Specification Tree.

3 Load Vector Set
This dialog section controls the specification of a Load Vector Set - a collection of 3D excitation arrays - as
load definition for the vibro-acoustic analysis. The Load Vector Set must be of type “Pressure” and must be applied
to the structural model. If you do not want to include the load vector set in the Vibro-Acoustic Response Analysis Case,
select the No Load Vector Set option. You can also either create a new load vector set or reference an existing one. Select
the Create a New Load Vector Set option to create a new load vector set, which then needs to be defined. Select the
Use an Existing One option, to reference an existing load vector set from the Specification Tree. Selecting this option
will activate a feature selection box below it in order to select the available load vector set from the Specification Tree.
Note that the Load Vector Set cannot be applied together with a boundary condition Set and/or a Load Function Set.

4 Acoustic Mode Set
This dialog section controls whether the acoustic response analysis will be executed using a direct approach or a modal-
based approach. If you do not want to include an acoustic mode set in the Vibro-Acoustic Response Analysis Case, select
the No Acoustic Mode Set option. You can also either create a new acoustic mode set or reference an existing one. Select
the Create a New Acoustic Mode Set option to create a new acoustic mode set, which then needs to be defined. Select the
Use an Existing One option, to reference an existing acoustic mode set from the Specification Tree. Selecting this option
will activate a feature selection box below it in order to select the available acoustic mode set from the Specification Tree.

5 Structural Mode Set
This dialog section controls the specification of a Structural Mode Set, which will describe the dynamical behavior of
the structure in the vibro-acoustic analysis. You can either create a new structural mode set or reference an existing
one. Select the Create a New Structural Mode Set option to create a new structural mode set, which then needs to be defined.
Select the Use an Existing One option, to reference an existing structural mode set from the Specification Tree. Selecting
this option will activate a feature selection box below it in order to select the available structural mode set from the
Specification Tree.

6 Wetted Surface
This dialog section controls the definition of the Wetted Surface for the Vibro-Acoustic Response Analysis Case, which
is defined as the part of the structure that is considered to be in contact with the acoustic fluid. In other words, the
Wetted Surface is nothing else than the fluid-structure interface between the acoustic and structural models. Hence, the
Wetted Surface defines the coupling between acoustics and structural dynamics. For the SYSNOISE background solver, the
Wetted Surface will define the elements that are part of the fluid-structure interface definition contained in the LINK
command.

You can either create a new wetted surface or reference an existing one. Select the Create a New IO Face Set option to
create a new wetted surface, which then needs to be defined. To define a Wetted Surface, you need to select a set of
IO Faces, which will mostly be either the Acoustic Mesh Part or a group of Boundary Elements. Select the Use an Existing
One option, to reference an existing wetted surface from the Specification Tree. Selecting this option will activate a
feature selection box below it in order to select the available wetted surface from the Specification Tree.




问题：
1、声压什么时候是三维向量了？让我看得一头雾水
2、湿表面选项在弹出的菜单下没有显示，取而代之的是 Mesh Mapping Set，这因该没有什么影响吧，都一样？【我用的是Vl10B】
3、我提交计算时遇到了Error:No physical type to transfer，又是什么原因呢？在做Uncoupled 分析的时候，需要将结构振动速度或者加速度Map到声腔表面进行计算，这个我理解；可是这里错误好像也有点那个意思，郁闷啊，十万火急啊




我现在能够算了；
问题出在结构模态的振型数据没有正确导入；通过hypermesh重新设置，再重新计算之后带入就行了。
Load step:
DISPLACEMENT(SORT1,PUNCH,REAL)=ALL
ESE(SORT1,PUNCH,PLOT)=ALL

superxjw

不清楚你具体模型是什么样的，是不是可以考虑耦合边界元？

mafuyin

节点是通过映射插值来对应的，即搜索最近的节点进行匹配。程序是这么运作的，如果你觉得这样做会对你的模型导致不可接受的误差，那么应当改变网格尺寸。

zhchyl999

理论结合实践   支持下

mxlzhenzhu

mafuyin 发表于 2012-4-8 08:54
节点是通过映射插值来对应的，即搜索最近的节点进行匹配。程序是这么运作的，如果你觉得这样做会对你的模型 ...

谢谢版主啊；我看了看的确是应该这样理解；要求完全Node to Node是不太现实的，否则前处理太麻烦了；进行 Vibro-Acoustic Mesh Mapping Set就是这种加权平均的思想。

mxlzhenzhu

superxjw 发表于 2012-4-7 22:27
不清楚你具体模型是什么样的，是不是可以考虑耦合边界元？

Superxjw你好；我做的FE/FE，也就算结构有限元和流体有限元的耦合；实例教程能够做，但是自己的东西却老是错误不断。

superxjw

mxlzhenzhu 发表于 2012-4-13 17:07
Superxjw你好；我做的FE/FE，也就算结构有限元和流体有限元的耦合；实例教程能够做，但是自己的东西却老 ...

我个人感觉，实例能做，但是自己做的东西不能算，90%以上都要考虑网格问题。