*HEADING
This problem same as iw_1d_ac2d4r_xpl_p_pa.inp except that the total wave 
formulation is used here.
 1D transient wave propagation, acoustic medium, incident wave load, planar
 and defined through pressure amplitude
**
** C = root (K/rho)= 343.05 m/s   K=bulk mod, rho=density.  
**
** Analytical 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
** 
*ACOUSTIC WAVE FORMULATION, TYPE=TOTAL WAVE
*PREPRINT,ECHO=NO,HISTORY=NO,MODEL=YES
*NODE, NSET=ODB_NSET
    1, 0,
  101, 1,
  501, 0, .5E-2
  601, 1, .5E-2
 1001, 0, 1.E-2
 1101, 1, 1.E-2
*NGEN,NSET=CHANNEL
    1,101
  501,601
 1001,1101
*NSET,NSET=SAMPLE,GENERATE
 1,101
*ELEMENT,TYPE=AC2D4R
 1,1,2,1002,1001
*ELGEN,ELSET=CHANNEL
 1,100
**************************
*SURFACE,NAME=IW_LOAD
1,S4
**************************
** CROSS-SECTION IS 1.E-4  
*SOLID SECTION,MATERIAL=AIR,ELSET=CHANNEL
 1.E-2, 
**
*MATERIAL,NAME=AIR
*DENSITY
 1.21,
*ACOUSTIC MEDIUM,BULK MODULUS
 0.1424E6,
**
**************************
*INCIDENT WAVE PROPERTY,NAME=IWPROP,TYPE=PLANE
0.0,0.0,
-10.0,0.0,
*INCIDENT WAVE FLUID PROPERTY
0.1424E6,1.21,0.0
*AMPLITUDE,DEFINITION=TABULAR,NAME=PRESSUREVTIME
0.0,0.0,1.0,1.0
**************************
*RESTART,WRITE
**
*STEP
*DYNAMIC,EXPLICIT
 ,.0044,
** DEFINE NONREFLECTIVE BOUNDARY AT X=1
*IMPEDANCE
 100,I2
**
*INCIDENT WAVE,PRESSUREAMPLITUDE=PRESSUREVTIME,PROPERTY=IWPROP
IW_LOAD,415.09517
**
*NSET,NSET=QA_TEST
ODB_NSET,
*OUTPUT,FIELD,NUMBER INTERVAL=2
*NODE OUTPUT
 POR,
*NODE OUTPUT,NSET=QA_TEST
 POR,
*OUTPUT,HISTORY,TIME INTERVAL=0.1E-3
*NODE OUTPUT,NSET=SAMPLE
 POR,
*ENDSTEP