*HEADING 
     Gas structure interaction with structure modeled using 2D elements.

This test verifies the coupling between cavity fluid pressure and deformation 
of the structure enclosing the fluid cavity.
The deformation of the structure should change the fluid pressure according to
the fluid behavior definition and the pressure should get transferred to the 
structure.  
Fluid cavity pressure x Area of any face of the structure  = 
        Sum of RF in a direction normal to the selected face on all the nodes 
        constituting that face.
*PHYSICAL CONSTANTS, ABSOLUTE ZERO=-273.16, UNIVERSAL GAS CONSTANT=8.314
**=============================================================================
**Cavity I: Structure enclosing cavity modeled using CPS4R, CPE4R, CPS3, CPE3,
            B21 ans T2D2 elements
**=============================================================================
*NODE, NSET=struct
11, 0, 0
12, 2, 0
13, 2.5, 0.5
14, 2, 1
15, 2.5, 1.5
16, 2, 2
17, 0, 2
18, -1, 2
19, -1, 1
110, 0, 1
111, -1, 0
**
**Cavity ref node
**
*NODE, NSET=struct_Ref
199, 1, 1
*NSET, NSET=structFix_BC
11, 12, 13, 14, 15, 19, 110, 111
*NSET, NSET=structDisp_BC
16, 17, 18
*ELEMENT, TYPE=CPS4R, ELSET=structPSQuad
11, 17, 18, 19, 110
*ELEMENT, TYPE=CPE4R, ELSET=structPEQuad
12, 11, 110, 19, 111
*ELEMENT, TYPE=CPE3, ELSET=structPETri
13, 12, 13, 14
*ELEMENT, TYPE=CPS3, ELSET=structPSTri
14, 14, 15, 16
*ELEMENT, TYPE=B21, ELSET=structBeam
15, 16, 17
*ELEMENT, TYPE=T2D2, ELSET=structTruss
16, 11, 12
*SURFACE, NAME=struct_Surf, TYPE=ELEMENT
11, S4
12, S1
13, S3
14, S3
15, SPOS
16, SPOS
**
**Fluid cavity definition
**
*FLUID CAVITY, NAME=struct_Cav, REF NODE=struct_Ref, BEHAVIOR=AIR, 
SURFACE=struct_Surf, AMBIENT PRESSURE=1.0E5
1
**=============================================================================
**Cavity II: Structure enclosing cavity modeled using R2D2 and CPS3 elements
**=============================================================================
*SYSTEM
4, 0, 0
*NODE, NSET=rigid
21, 0, 0
22, 2, 0
23, 2, 2
24, 0, 2
27, -1, 1
28, 3, 1
**
**Cavity ref node
**
*NODE, NSET=rigid_Ref
299, 1, 1
*NODE, NSET=rigid1_Ref
25, 1, -1
*NODE, NSET=rigid2_Ref
26, 1, 3
*ELEMENT, TYPE=CPS3, ELSET=rigidPS
21, 21, 24, 27
22, 23, 22, 28
*ELEMENT, TYPE=R2D2, ELSET=rigid1
23, 21, 22
*ELEMENT, TYPE=R2D2, ELSET=rigid2
24, 23, 24
*SURFACE, NAME=rigid_Surf, TYPE=ELEMENT
21, S1
22, S1
23, SPOS
24, SPOS
**
**Fluid cavity definition
**
*FLUID CAVITY, NAME=rigid_Cav, REF NODE=rigid_Ref, BEHAVIOR=AIR, 
SURFACE=rigid_Surf, AMBIENT PRESSURE=1.0E5
1
**
**Fluid behavior definition
**
*FLUID BEHAVIOR, NAME=AIR
*MOLECULAR WEIGHT
0.0289
*CAPACITY, TYPE=POLYNOMIAL
28.110, 1.967E-3, 4.802E-6, -1.966E-9, 0.0
**
**Section assignment
**
*BEAM SECTION, ELSET=structBeam, SECTION=RECT, MATERIAL=MAT
1,.1 
*ELSET, ELSET=struct
11, 12, 13, 14, 16
*SOLID SECTION, ELSET=struct, MATERIAL=MAT
1
*SOLID SECTION, ELSET=rigidPS, MATERIAL=MAT
1
*RIGID BODY, REF NODE=rigid1_Ref, ELSET=rigid1
1
*RIGID BODY, REF NODE=rigid2_Ref, ELSET=rigid2
1
**
**Boundary conditions
**
*BOUNDARY
structFix_BC, 1, 2
structDisp_BC, 1, 2
16, 6, 6
17, 6, 6
*BOUNDARY
rigid1_Ref, 1, 2
rigid2_Ref, 1, 2
27, 1, 2
28, 1, 2
**
**Initial conditions
**
*INITIAL CONDITIONS, TYPE=TEMPERATURE
struct_Ref, 20
rigid_Ref, 20
*INITIAL CONDITIONS, TYPE=FLUID PRESSURE
struct_Ref, 4.0E5
rigid_Ref, 4.0E5
**
**Material defintion
**
*MATERIAL, NAME=MAT
*DENSITY
5000
*ELASTIC
2E-10, 0.1
**
**Creat node sets
**
*NSET, NSET=qa_test_struct_Ref
struct_Ref
*NSET, NSET=qa_test_rigid_Ref
rigid_Ref
*NSET, NSET=qa_test_structRF
struct
*NSET, NSET=qa_test_rigidRF
rigid1_Ref, rigid2_Ref
**
** Amplitude definition
**
*AMPLITUDE, NAME=RAMP
0, 0, 1, 1
**
**Step 1: Apply displacement BC of 0.50 to all the nodes of a particular face 
**        with normal in +2 direction.
**
*STEP
*DYNAMIC, EXPLICIT, DIRECT USER CONTROL
0.001, 1
*BOUNDARY, OP=MOD, AMPLITUDE=RAMP
structDisp_BC, 2, 2, 0.50
rigid2_Ref, 2, 2, 0.50
*OUTPUT, HISTORY, TIME INTERVAL=0.25
*NODE OUTPUT, NSET=qa_test_struct_Ref
PCAV, CVOL
*NODE OUTPUT, NSET=qa_test_rigid_Ref
PCAV, CVOL
*NODE OUTPUT, NSET=qa_test_structRF
RF1, RF2
*NODE OUTPUT, NSET=qa_test_rigidRF
RF2
*NODE OUTPUT, NSET=structDisp_BC
U2
*NODE OUTPUT, NSET=rigid1_Ref
U2
*END STEP
**
**Step 2: Apply displacement BC of -0.50 
**        All the parameters e.g. CVOL, PCAV, RF's at the end of this step 
**        will be the same as at the beginning of Step 1. 
**
*STEP
*DYNAMIC, EXPLICIT, DIRECT USER CONTROL
0.001, 1
*BOUNDARY, OP=MOD, AMPLITUDE=RAMP
structDisp_BC, 2, 2, -0.50
rigid2_Ref, 2, 2, -0.50
*END STEP