流固耦合的模态分析的建模问题
我的问题是：对水中做自由振动一个矩形板的模态分析，求其在水中的固有频率和主振形（mode shape）我用ansys的建模方式是：（参照了例子vm177）
将模型建了三层，中间的是矩形板（SOLID45），上下两层是流体（FLUID30），使用模态分析求解(ANTYPE,MODAL). 但是我的模型计算的结果明显不对，都是0
本人还是个初学者，恳求大虾们不吝赐教，求教这类问题应该如何建模
________________
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| | <----- fluid elementFLUID30
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|_ ____________|
|___ __________| <------ plate SOLID45
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| | <------ fluidelementFLUID30 |
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|_____________|
付我的code（关键程序都注释了，可惜不对，结果都是0）
/PREP7
/TITLE, NATURAL FREQUENCY OF SUBMERGED plate
!--------------------------------------------------------------------------
p_length =100 !length
p_width = 50 !half of width
p_E =1.5e11 !Young's Modulus
p_D =2330 !Density of plate
p_P =0.17 !Poisson's ratios
f_D = 0.998 !Density of water
f_C = 344 !sound speed in water
p_thickness = 5 !the thickness of plate
!--------------------------------------------------------------------------
ET, 1, FLUID30 ! FLUID ELEMENTS INTERFACING WITH STRUCTURE
ET, 2, SOLID45 ! SHELL ELEMENTS TO MODEL STEEL RING
ET, 3, FLUID30, ,1 ! NON-INTERFACING FLUID ELEMENTS
R,1,1 !the reference pressure of fluid
! water properties
MP, DENS , 1, f_D
MP, SONC , 1, f_C ! SPEED OF SOUND IN WATER
! plate properties
MP, EX, 2, p_E
MP, DENS, 2, p_D
MP, NUXY, 2, p_P
!---------------------------------------------------------------------------
BLC4, 0, -50, 100, 100, p_thickness!create the plate
WPAVE, , , p_thickness
BLC4, 0, -50, 100, 100, 200 !create the top fluid bulk
WPAVE, 0, 0, 0
BLC4, 0, -50, 100, 100, -200 !create the bottom fluid bulk
TYPE,1
MAT,1
REAL,1
ESIZE, , 16
VMESH, 2
VMESH,3 !Mesh the fluid by usingthe FLUID30
TYPE,2
MAT,2
REAL,2
ESIZE, , 16
VMESH,1 !Mesh the plate by usingthe SOLID45
NSEL, S, LOC, Y, 0 !select middle nodes(which Y=0)
NSEL, R, LOC, Z, 0
M, ALL, UZ !Defines master degrees of freedom
NSEL, S, LOC, X, 0
NSEL, R, LOC, Z, 0
D,ALL,ALL !DOF constrains (clamped)
!---------------------------------------------------------------
ESEL,ALL
NSEL,S,LOC,Z,0
NSEL,A,LOC,Z,p_thickness
ESLN
ESEL,INVE
TYPE,3
MAT,1
REAL,1
EMODIF,ALL !define uncoupled fluid elements
!define fluid-structure interface
NSEL, ALL
ESEL, S, TYPE, , 1
!fluid-structure interaction flag
NSEL, S, LOC, Z, 0
NSEL, A, LOC, Z, p_thickness
SF,ALL,FSI ! COUPLE STRUCTURAL MOTION & FLUID PRESS
! SET PRESSURE AT OUTER SURFACE TO ZERO
NSEL, S, LOC, Z, 200-p_thickness
NSEL, A, LOC, Z, -200
D, ALL, PRES, 0.0 !SET PRESSURE AT OUTER RADIUS TO ZERO
NSEL,ALL
ESEL,ALL
!OUTPR,ALL, 1 !Print out every items for every substeps
FINISH
/SOLU
ANTYPE,MODAL ! MODAL ANALYSIS
MODOPT,UNSYM,4,-100 ! SELECT UNSYMMETRIC MATRIX MODE EXTRACTION
MXPAND,,0.1,10000 ! EXPAND THE MODES OVER A SELECTED FREQUENCY
RANGE
SOLVE ! Solve the problem
/POST1
SET,FIRST,1 ! Read the first step result(fundamental
frequency)
PLDISP,1 ! Display the mode shape
! save the first frequency to files
*GET, Freq, ACTIVE, 0, SET, FREQ
/OUT, Result_MA_P_F, vrt, ,
*VWRITE, Freq
(F10.4)
/OUT
FINISH
*LIST, Result_MA_P_F, vrt!print out results
[ 本帖最后由 alber2008 于 2007-4-30 17:03 编辑 ] 这个应该不是很复杂的问题吧，nobody knows??? upupupupupupupupupupupupupup upupupupupupupupupupupupupup 你的分析系统是什么，你想求解流体加上固体这么一个系统的固有频率吗，显然是不对的，你这样的分析，没有搞清楚分析的目标是什么，到底是流体还是结构
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