关于流固耦合的界面问题

yu0516010129

本人在编一个简单的例子，要求一个方块在水中（圆柱形）的模态，耦合的有点问题。。
命令如下
finish
/clear
/prep7
et,1,solid45
et,2,fluid30
et,3,fluid30,,1
mp,ex,1,2e11
mp,nuxy,1,0.3
mp,dens,1,7800
mp,dens,2,1000
mp,sonc,2,1400
mp,mu,0,

blc4,-0.5,-0.5,1,1,2
esize,,4
lsel,s,length,,2
lesize,all,,,8
allsel,all
mshkey,1
type,1
mat,1
vmesh,all

wpoff,,,-1
PCIRC,1.5, ,-45,45,  
voffst,7,4
FLST,5,6,4,ORDE,2   
FITEM,5,13
FITEM,5,-18
LSEL,S,,,P51X
lesize,all,,,6
allsel,all
lsel,s,length,,4
lesize,all,,,16
allsel,all
type,3
mat,2
mshape,0,3D
mshkey,1
vmesh,2
wpcsys,-1

ESEL,S,MAT,,2   
eplot   
NSLE,R
csys,1
ngen,4,791,all,,,,90
allsel,all
csys,0

ESEL,S,MAT,,2   
eplot  
egen,4,791,all

ESEL,S,MAT,,2   
eplot   
NSLE,R

nummrg,node
allsel,all


csys,1  
NSEL,S,LOC,X,1.5,1.5
csys,0
nsel,a,loc,z,-1
nsel,a,loc,z,3
d,all,pres,0
alls
ESEL,S,MAT,,1
asel,s,loc,z
asel,a,loc,z,2
asel,a,loc,x,0.5
asel,a,loc,x,-0.5
asel,a,loc,y,0.5
asel,a,loc,y,-0.5
nsla,s,1
esln,s,0
emodif,all,type,2
sf,all,fsi !
alls
fini
/solu
antype,2
modopt,unsym,10,-100,,   
mxpand,10,1,1000
solv

solv完出的提示
*** ERROR ***                           CP =     106.984   TIME= 15:14:39
Element 1 references undefined SONC of material 1.   

请问：MAT1是固体的，也没有声速啊，还是耦合的问题吧？还望高手指点指点。。。