转贴:有兴趣研究一下
我按照ansys里给的一个例子做的,就是15.9. Example 1: Fluid-Structure Coupled Acoustic Analysis (Command Method)
这是我自己做的,计算是总是出现下面这个问题:
*** WARNING *** CP = 1660.953 TIME= 21:54:16
Coefficient ratio exceeds 1.0e8 - Check results.
*** WARNING *** CP = 2096.797 TIME= 22:02:00
There are 1 positive pivots with ratios less than 1.E-13 indicating a
possible poorly conditioned stiffness matrix.
不知道怎么回事,郁闷了很久了,各位大虾帮忙看看吧,谢谢了!
下面是我做的命令:
/BATCH,LIST
/PREP7
/TITLE,vibration of pipe with fluid in
!单元
et,1,42,,,3
et,2,45
et,3,29
et,4,30,,0 ! structure present
et,5,30,,1 ! structure absent
r,1,0.0036
!材料
mp,ex,1,69e9
mp,dens,1,2700
MP,DENS,2,1030
MP,SONC,2,1460
!建模、分网
cyl4,,,0.0228,,0.0248
lesize,all,,,8
mshkey,2
mshape,0,2d
aatt,1,,1
amesh,all
cyl4,,,0.0228
asel,s,,,2
lsla,s
lesize,all,,,8
mshkey,0
mshape,0,2d
aatt,2,,3
amesh,all
allsel
!由面单元生成体单元
asel,s,,,1
extopt,attr,1,1,1
extopt,esize,200
extopt,aclear,1
type,2
vext,all,,,,,0.849
allsel
asel,s,,,2
extopt,attr,1,1,1
extopt,esize,200
extopt,aclear,1
type,4
vext,all,,,,,0.849
allsel
!单元属性修改
esel,s,type,,4
nsle,s,all
csys,1
nsel,s,loc,x,0.0228
esln,s,0,all
esel,inve
nsle,s
emodif,all,type,5
allsel
!流固耦合单元标识
nummrg,node
csys,1
nsel,s,loc,x,0.0228
sf,all,fsi,1
allsel
finish
!模态计算
/solu
antype,2
modopt,unsym,20,0,10000
mxpand,20,0,10000
solv |