流固耦合，请教版主，各位高手，弹簧单元怎么用呀？
版主：我用势流体做流固耦合，为了得到上下流动的自由表面，在上表面个点上（points不是nodes）上加弹簧单元，可是怎么会有这么多错误呢？怎么回事儿呢？
救救我吧！
*** STIFFNESS MATRIX NOT POSITIVE DEFINITE ***
NODE= 24 EQUATION= 49DOF= FLUID POTENT.PIVOT= -2.19406530E+04
NODE= 394 EQUATION= 759DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 456 EQUATION= 761DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 458 EQUATION= 763DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 460 EQUATION= 765DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 462 EQUATION= 767DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 464 EQUATION= 769DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 466 EQUATION= 771DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 468 EQUATION= 773DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 470 EQUATION= 775DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
NODE= 472 EQUATION= 777DOF= Y-TRANSLATIONPIVOT=0.00000000E+00
*** IN SMALL DISPLACEMENT LINEAR ELASTIC ANALYSIS ***
CHECK THE FOLLOWING --
(A) BOUNDARY CONDITIONS -
THE B.C. MUST NOT ADMIT A RIGID BODY
DISPLACEMENT OR ROTATION OF THE TOTAL
STRUCTURE.
(B) DELETION OF DEGREES-OF-FREEDOM -
ALL D.O.F. AT NODAL POINTS WITHOUT
STIFFNESS CONTRIBUTIONS FROM ELEMENTS
MUST HAVE BEEN DELETED.
(C) ELEMENT GEOMETRY AND CONNECTIVITY -
ALL ELEMENTS MUST HAVE BEEN INPUT WITH
PROPER NODAL NUMBERS, AS DESCRIBED IN
THE USERS MANUAL.
(D) ELEMENT INTEGRATION ORDERS -
THE ORDERS OF NUMERICAL INTEGRATIONS FOR
EVALUATION OF ELEMENT MATRICES MUST BE
SUFFICIENTLY HIGH.
(E) MATERIAL DATA -
ALL MATERIAL DATA MUST BE PHYSICALLY
REASONABLE (E.G. YOUNG*S MODULUS MUST
BE GREATER THAN ZERO).
*** IN MATERIALLY NONLINEAR AND/OR LARGE DISPLACEMENTANALYSIS ***
IF THE MODEL HAS BEEN INPUT CORRECTLY (WITH ALL
THE ABOVE CONSIDERATIONS TAKEN INTO ACCOUNT), THEN
THE COLLAPSE LOAD OF THE MODEL HAS BEEN REACHED. http://forum.simwe.com/thread-742373-1-1.html
http://forum.simwe.com/thread-742377-1-1.html
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