*HEADING
EC23AFAS: 1D transient wave propagation in an acoustic medium with prescribed Acceleration on DOF 1.
 AC2D3,ASI2
 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=YES,MODEL=YES
*NODE, Nset=ODB_NSET
*NGEN,NSET=CHANNEL
*NSET,NSET=SAMPLE,GENERATE
*NSET,NSET=LOAD
*ELEMENT,TYPE=AC2D3
*ELGEN,ELSET=CHANNEL
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
 1.e-2,
*surface,NAME=NRS
 199,S2
** Cr-sec is 1e-4
** ASI element at x=0, so that acceleration may be prescribed
** directly:
*ELEMENT,TYPE=ASI2,ELSET=LOAD
*INTERFACE,ELSET=LOAD
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
**
**
*RESTART,WRITE
*Elset,Elset=ODB_ESET
CHANNEL,
*Nset, Nset=ODB_NSET
ODB_NSET, CHANNEL, SAMPLE, LOAD
**
*STEP,INC=1000
*DYNAMIC
.0001,.0036
** Define nonreflective boundary at x=1
*IMPEDANCE
 199,I2,
**
** Prescribe volume acceleration inwards
**   of  a0=1.
** Acceleration of interface element specified.
*BOUNDARY,TYPE=ACCELERATION
 LOAD,1,1,1.
*EL PRINT,FREQ=0
*NODE PRINT,NSET=SAMPLE,FREQ=6
 POR,
*NODE FILE,NSET=SAMPLE,FREQ=6
 POR,
*OUTPUT,FIELD,VARIABLE=PRESELECT,OP=ADD,FREQUENCY=9999
*OUTPUT,FIELD, OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE
 POR,
*OUTPUT,HISTORY,OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE
 POR,
*ENDSTEP
**************
*STEP,INC=1000
*DYNAMIC
.0001,.0008
*IMPEDANCE,OP=NEW
*SIMPEDANCE
 NRS,
*BOUNDARY,TYPE=ACCELERATION
 LOAD,1,1,1.
*EL PRINT,FREQ=0
*NODE PRINT,NSET=SAMPLE,FREQ=6
 POR,
*NODE FILE,NSET=SAMPLE,FREQ=6
 POR,
*OUTPUT,FIELD,VARIABLE=PRESELECT,OP=ADD,FREQUENCY=9999
*OUTPUT,FIELD, OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE
 POR,
*OUTPUT,HISTORY,OP=ADD,Frequency=6
*NODE OUTPUT,NSET=SAMPLE
 POR,
*ENDSTEP