*HEADING
 EC34AFAS: AC3D4 and 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=no
*NODE, Nset=ODB_NSET
*NGEN,NSET=CHANNEL_NODES
*NSET,NSET=SAMPLE_NODES,GENERATE
*NSET,NSET=LOADED
*ELEMENT,TYPE=AC3D4
*ELGEN,ELSET=CHANNEL
**
** note that the ASI4 elements are degenerated
** to 3 - noded geometry. "ASI3" is a quadratic
** line element.
**
*ELEMENT,TYPE=ASI4,ELSET=LOAD
*INTERFACE,ELSET=LOAD
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
*surface,NAME=NRS
 597,S4
 596,S2
**
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
**
*RESTART,WRITE
*Elset,Elset=ODB_ESET
CHANNEL,
*Nset, Nset=ODB_NSET
ODB_NSET, CHANNEL_NODES, SAMPLE_NODES, LOADED
**
*STEP,INC=1000
*DYNAMIC
.0001,.0036
*IMPEDANCE
 597,I4,
 596,I2,
**
*BOUNDARY,TYPE=ACCELERATION
 LOADED,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,FREQ=1
*OUTPUT,FIELD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE_NODES
 POR,
*OUTPUT,HISTORY,Frequency=6
*NODE OUTPUT,NSET=SAMPLE_NODES
 POR,
*ENDSTEP
**
*STEP,INC=1000
*DYNAMIC
.0001,.0008
*IMPEDANCE,OP=NEW
*SIMPEDANCE
 NRS,
*BOUNDARY,TYPE=ACCELERATION
 LOADED,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,FREQ=1
*OUTPUT,FIELD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE_NODES
 POR,
*OUTPUT,HISTORY,Frequency=6
*NODE OUTPUT,NSET=SAMPLE_NODES
 POR,
*ENDSTEP