*HEADING
 EC36AFAS: AC3D6 & ASI4
 1D transient wave propagation in an acoustic medium
 with prescribed acceleration on dof 1.
 Verification problem: Transient Dynamics Tests
**
** C = root (K/rho)= 343.05 m/s   K=bulk mod, rho=density.
**
** Analytic solution to prescribed constant acceleration of a0 at x=0
**
** p(x,t) = (K a0 / c^2) (ct - x)  for x < ct
**        = 0  			   for x > ct
**
*PREPRINT,ECHO=NO,HISTORY=NO,MODEL=YES
*NODE, Nset=ODB_NSET
*NGEN,NSET=CHANNEL_NODES
*NSET,NSET=SAMPLE_NODES,GENERATE
*NSET,NSET=LOADED_NODES
*ELEMENT,TYPE=AC3D6
*ELGEN,ELSET=CHANNEL
*ELEMENT,TYPE=ASI4,ELSET=LOAD
*INTERFACE,ELSET=LOAD
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
*surface,NAME=NRS
 199,S4
**
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS,DEP=1
**
*RESTART,WRITE
*Elset,Elset=ODB_ESET
CHANNEL,
*Nset, Nset=ODB_NSET
ODB_NSET, CHANNEL_NODES, SAMPLE_NODES, LOADED_NODES
**
*INITIAL CONDITIONS,TYPE=FIELD
CHANNEL_NODES,1
*INITIAL CONDITIONS,TYPE=TEMPERATURE
CHANNEL_NODES,20
**
*STEP,INC=1000
*DYNAMIC
.0001,.0036
*IMPEDANCE
 199,I4,
**
** Prescribe  acceleration inwards of  a0=1.
**
*BOUNDARY,TYPE=ACCELERATION
 LOADED_NODES,1,1,1.00
**
*EL PRINT,FREQ=0
*NODE PRINT,NSET=SAMPLE_NODES,FREQ=6
 POR,
*NODE FILE,NSET=SAMPLE_NODES,FREQ=6
 POR,
*OUTPUT,FIELD,VARIABLE=PRESELECT,OP=ADD,FREQUENCY=9999
*OUTPUT,FIELD, OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE_NODES
 POR,
*OUTPUT,HISTORY,OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE_NODES
 POR,
*ENDSTEP
**
*STEP,INC=1000
*DYNAMIC
.0001,.0008
*IMPEDANCE,OP=NEW
*SIMPEDANCE
 NRS,
**
** Prescribe  acceleration inwards of  a0=1.
**
*BOUNDARY,TYPE=ACCELERATION
 LOADED_NODES,1,1,1.00
**
*EL PRINT,FREQ=0
*NODE PRINT,NSET=SAMPLE_NODES,FREQ=6
 POR,
*NODE FILE,NSET=SAMPLE_NODES,FREQ=6
 POR,
*OUTPUT,FIELD,VARIABLE=PRESELECT,OP=ADD,FREQUENCY=9999
*OUTPUT,FIELD, OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE_NODES
 POR,
*OUTPUT,HISTORY,OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE_NODES
 POR,
*ENDSTEP