*parameter 
Density = 1.21
Acous_bulk_mod = 0.1424E6
Volume_drag =  1.e4
Cross_section  = 3.0
**------------------------------------------------
*preprint,echo=yes,model=yes,hist=yes
*NODE,NSET=PR
1,0,0,0
101,1,0,0
**------------------------------------------------
*USER ELEMENT,NODES=2,TYPE=VU2,PROPERTIES=4,COORDINATES=3,VARIABLES=2
8,
*ELEMENT,TYPE=VU2,elset=CHANNEL
201 , 1, 101
*UEL PROPERTY,ELSET=CHANNEL
<Cross_section>, <Density>, <Acous_bulk_mod>, <Volume_drag>
**------------------------------------------------
*step, nlgeom=yes
*dynamic,explicit
**,direct
,1.e-2
** Prescribe volume acceleration inwards
**  of  a0 * cross-section = 3., therefore a0=1
*CLOAD
 1,8, <Cross_section>
***boundary
**101,8,8,1.23
*output,field,var=preselect,freq=0
*output, history, freq=1
*node output,nset=PR
por,
*energy output
*END STEP
**------------------------------------------------