# Displacement is too large...

1. Mar 13, 2016

### zhaomu67

1. The problem statement, all variables and given/known data
hi,i am using pipe289 to simulate a marine riser in ansys,
the length of marine riser:1000m
the outside diameter of marine riser:0.5334m
the thickness of marine riser:0.0254
the velocity of current:1m/s
the wave peroid:8s
the wave height:6.5m
boudary conditions: ux/uy on node 1 and ux/uy/uz on node 2, a force(5e6) was applied on node 1
2. Relevant equations
N/A

3. The attempt at a solution
after i set the boudary conditions and ocean loads, the displacement is very large(1000m),i have tried to change the variables, i found the velocity of current has a big difference to the result, Can someone help ? Much appreciated thanks!

Mod note: The following is contained in the attached file.
Code (Text):

/FILENAME,RISER,1
/TITLE,RISER

DWATER=1000
H_WAVE=6.5
T_WAVE=8
V_SURFACE=1
V_MIDDLE=0.5
V_BOTTOM=0
RISMAT=1
MATWAT=2
FLUWAT=3

OD=0.5334
TW=0.0254

T_TOP=5e6

/PREP7
ET,1,PIPE289
KEYOPT,1,1,0
KEYOPT,1,4,2
KEYOPT,1,6,1
KEYOPT,1,7,0
KEYOPT,1,8,0
KEYOPT,1,9,2
KEYOPT,1,11,3
KEYOPT,1,12,1
KEYOPT,1,15,0

MP,EX,1,2.1E11
MP,PRXY,1,0.3
MP,DENS,1,7850
MP,DENS,2,1030
MP,DENS,3,1200

SECTYPE,SECPIPE,PIPE,,riser
SECDATA,OD,TW,16,0,3,FLUWAT,0,0
OCTYPE,BASIC
ocdata,DWATER,MATWAT,0,1,1,1,0
octable,,,0.5,0.5,,2,2
octype,curr
octable,0,V_SURFACE
octable,-500,V_MIDDLE
octable,-DWATER,0.0
octype,wave
ocdata,2
octable,H_WAVE,T_WAVE,58
CSYS,0
K,1,0,0,0
K,2,0,0,-DWATER
LSTR,1,2
LSEL,S,LINE,,1
LATT,1,1,1
LESIZE,ALL,1,,,,,,
LMESH,ALL
ALLSEL
SAVE
FINISH

/SOLU
ANTYPE,0
NSEL,S,LOC,Z,-DWATER
D,ALL,UX
D,ALL,UY
D,ALL,UZ
D,ALL,ROTZ
ALLSEL
NSEL,S,LOC,Z,0
D,ALL,UX
D,ALL,UY
ALLSEL
NSEL,S,LOC,Z,0
F,ALL,FZ,F_TOP
ALLSEL
ACEL,0,0,9.8

TIME,1
SOLVE
SAVE
FINISH

/POST1
SET,LAST
PLDISP,O

#### Attached Files:

• ###### pipe289.txt
File size:
1 KB
Views:
39
Last edited by a moderator: Mar 13, 2016
2. Mar 14, 2016

### SteamKing

Staff Emeritus
Is there a sketch showing this riser and how it is restrained and loaded? Trying to decipher a data file is less than ideal.