*Heading
2D model of Box with Air
Adaptive mesh used to update Air
2D continuum elements tested
**------------------------------------------------
*Node
*Element, type=AC2D4
*Elset, elset=AIR-1__I1
*solidsection, elset=AIR-1__I1, material=AIR
** ----------------------------------------------------------------
*Node
*Element, type=CPS4
*Elset, elset=BOX-1__I1
*solidsection, elset=BOX-1__I1, material=SOLID
*surface, type=ELEMENT, name=AIR
AIR_S1, S1
AIR_S2, S2
AIR_S4, S4
AIR_S3, S3
*surface, type=ELEMENT, name=SOLID-S
SOLID-S_S4, S4
SOLID-S_S1, S1
SOLID-S_S2, S2
*tie, name=AIR-SOLID, adjust=YES
AIR, SOLID-S
**
** Assembly Nsets
**
*Nset, nset=AIR
*Nset, nset=CLOAD1
*Nset, nset=LEFT
*Nset, nset=RIGHT
*Nset, nset=LOAD
*nset, nset=retained
*Nset, nset=OUT_AIR
*Nset, nset=OUT_BOX
*Nset, nset=SIR_S
*Nset, nset=SOLID_S
*Nset, nset=SET10
**
** Assembly Elsets
**
*Elset, elset=AIR
*Elset, elset=SIR_S
*Elset, elset=SOLID_S
*Elset, elset=AIR_S1
*Elset, elset=AIR_S2
*Elset, elset=AIR_S3
*Elset, elset=AIR_S4
*Elset, elset=SET10
*Elset, elset=SOLID-S_S1
*Elset, elset=SOLID-S_S2
*Elset, elset=SOLID-S_S4
*material, name=AIR
*acousticmedium
*density
1.1E-3,
*material, name=SOLID
*density
0.01,
*elastic
100, 0.
*boundary
87, 1, 2
84, 1, 2
*amplitude,name=const
0,1.0,  1.0,1.0
*amplitude,name=constIm
0,1.0,  1.0,1.0
*Step, nlgeom
*static
0.2, 1., 1E-05, 1.
*DLOAD
SOLID-S_S4, P4,0.2
SOLID-S_S1, P1,0.2
SOLID-S_S2, P2,0.2
*adaptivemesh, frequency=1, meshsweeps=10, elset=AIR
*print, adaptivemesh=YES
*output, field
*elementoutput
S
*nodeoutput
U
*output, history, variable=PRESELECT
*endstep
**------------------------------------------------
*Step,perturbation
*frequency,norm=mass
** 189,,,-1
** calculation of eigenmodes 118..189 is unstable and can introduce
** small perturbations in the QA results
117,,,-1
*boundary,op=new
87,1,2
84,1,2
*boundary,base name=excit1
88,1,1
89,1,1
*boundary,base name=excit2
88,2,2
89,2,2
*output, field,mode list
*node output
u,por
*endstep
****------------------------------------------------
*Step, perturbation
*steadystatedynamics, interval=RANGE
*base motion,dof=1,REAL,amplitude=const,base name=excit1,type=disp
*base motion,dof=2,IMAGINARY,amplitude=constIm,base name=excit2,type=disp
*output, field, frequency=0
*output, history
*nodeoutput, nset=OUT_BOX
U,
*nodeoutput, nset=OUT_AIR
POR,
*endstep
**------------------------------------------------
*Step, perturbation
*steadystatedynamics, subspaceprojection, interval=RANGE
*base motion,dof=1,REAL,amplitude=const,base name=excit1,type=disp
*base motion,dof=2,IMAGINARY,amplitude=constIm,base name=excit2,type=disp
*output, field, frequency=0
*output, history
*nodeoutput, nset=OUT_BOX
U,
*nodeoutput, nset=OUT_AIR
POR,
*endstep
**------------------------------------------------
*Step, perturbation
*steadystatedynamics, direct, interval=RANGE
*boundary,op=new
87,1,2
84,1,2
*boundary, op=new, amplitude=const,REAL
88, 1, 1, 1.0
89, 1, 1, 1.0
*boundary, op=new, amplitude=constIm,IMAGINARY
88, 2, 2, 1.0
89, 2, 2, 1.0
*output, field, frequency=0
*output, history
*nodeoutput, nset=OUT_BOX
U,
*nodeoutput, nset=OUT_AIR
POR,
*nodeoutput, nset=retained
U,RF
*endstep
****------------------------------------------------
*STEP,UNSYM=YES
*MATRIX GENERATE,STIFFNESS,MASS,LOAD
*boundary, op=new, amplitude=const,REAL
88, 1, 1, 1.0
89, 1, 1, 1.0
*boundary, op=new, amplitude=constIm,IMAGINARY
88, 2, 2, 1.0
89, 2, 2, 1.0
*END STEP