SPH particles not interacting with one another.

- August 3, 2023 at 2:36 pm
  
  Caleb Wood
  Subscriber
  
  Hello,
  I am trying to simulate a wave tank using the SPH method. The model consists of a contained made of rigid 3D elements, a piston made of rigid shell elements, and water modelled with SPH particles. The issue I am having is when I apply gravity to the model using LOAD_BODY_Z and a load curve of 9.81 m/s^2, the particles collapse to the ground. This is illustraded in the attached screen shots. Note that there is no leakage from the container, the particles simply fall straight down. Any help on this issue would be greatly appreciated. Thank you!
- August 4, 2023 at 1:40 pm
  
  Ram Gopisetti
  Ansys Employee
  
  Hi,
  How the wate is constriained?
  cheers, ram
  - August 8, 2023 at 4:42 pm
    
    Caleb Wood
    Subscriber
    
    Hi, apologies for the late reply. I have since been able to model the wave tank but now there appears to be another issue, which is the amount of particle mixing. With the piston (wave maker) deactivated, the only load which the particles are subjected to is a gravity loading, applied with the LOAD_BODY_Z keyword. In my mind, if there are no loads directly applied to the water within the tank then there should be no particle movement, but thats not the case. The particles appear to move spuradically and I do not know why. I have attached screenshots as well as my keyword input file (note that the piston is active in this file) to illustrate this. If you know how to correct this issue I would greatly appreciate a response. Also, please ignore part #6 contained in the file, it does not make contact with anything and is only there to serve as a visual aid on the wave height.
    IMAGES WITH ONLY GRAVITY LOADING APPLIED
    KEYWORD INPUT FILE
    $# LS-DYNA Keyword file created by LS-PrePost(R) V4.9.12-16Dec2022
    $# Created on Aug-8-2023 (13:38:55)
    *KEYWORD
    *TITLE
    $# title
    LS-DYNA keyword deck by LS-PrePost
    *CONTROL_BULK_VISCOSITY
    $# q1 q2 type btype tstype
    0.0011.0000E-12 1 0 0
    *CONTROL_SPH
    $# ncbs boxid dt idim nmneigh form start maxv
    1 11.00000E20 3 500 15 0.01.00000E15
    $# cont deriv ini ishow ierod icont iavis isymp
    0 0 0 0 0 0 1 100
    *CONTROL_TERMINATION
    $# endtim endcyc dtmin endeng endmas nosol
    15.0 0 0.0 0.01.000000E8 0
    *CONTROL_UNITS
    $# length time mass temp
    m sec kg k
    *DATABASE_BINARY_D3PLOT
    $# dt lcdt beam npltc psetid
    0.01 0 0 0 0
    $# ioopt rate cutoff window type pset
    0 0 0
    *BOUNDARY_PRESCRIBED_MOTION_SET_ID
    $# id heading
    0Piston Motion
    $# nsid dof vad lcid sf vid death birth
    11 1 2 2 1.0 01.00000E28 0.0
    *LOAD_BODY_Z
    $# lcid sf lciddr xc yc zc cid
    1 9.81 0 0.0 0.0 0.0 0
    *PART
    $# title
    SphNode
    $# pid secid mid eosid hgid grav adpopt tmid
    1 1 1 1 0 0 0 0
    *SECTION_SPH_TITLE
    Water
    $# secid cslh hmin hmax sphini death start sphkern
    1 1.3 0.2 2.0 0.01.00000E20 0.0 0
    *MAT_NULL_TITLE
    Water
    $# mid ro pc mu terod cerod ym pr
    1 997.0 -10.0 0.001 0.0 0.0 0.0 0.0
    *EOS_MURNAGHAN_TITLE
    Water
    $# eosid gamma k0 v0
    1 7.0 65000.0 1.0
    *PART
    $# title
    Piston
    $# pid secid mid eosid hgid grav adpopt tmid
    4 2 2 0 0 0 0 0
    *SECTION_SHELL_TITLE
    Piston
    $# secid elform shrf nip propt qr/irid icomp setyp
    2 16 1.0 2 1.0 0 0 1
    $# t1 t2 t3 t4 nloc marea idof edgset
    0.2 0.2 0.2 0.2 0.0 0.0 0.0 0
    *MAT_RIGID_TITLE
    Piston
    $# mid ro e pr n couple m alias
    2 100.0 20000.0 0.25 0.0 0.0 0.0
    $# cmo con1 con2
    1.0 5 7
    $#lco or a1 a2 a3 v1 v2 v3
    0.0
    *PART
    $# title
    Container
    $# pid secid mid eosid hgid grav adpopt tmid
    5 2 4 0 0 0 0 0
    *MAT_RIGID_TITLE
    Container V2
    $# mid ro e pr n couple m alias
    4 100.0 20000.0 0.25 0.0 0.0 0.0
    $# cmo con1 con2
    1.0 7 7
    $#lco or a1 a2 a3 v1 v2 v3
    0.0
    *PART
    $# title
    Wave Height
    $# pid secid mid eosid hgid grav adpopt tmid
    6 2 4 0 0 0 0 0
    *HOURGLASS_TITLE
    Water
    $# hgid ihq qm ibq q1 q2 qb/vdc qw
    1 11.00000E-6 0 1.5 0.06 0.1 0.1
    *MAT_RIGID_TITLE
    Container
    $# mid ro e pr n couple m alias
    3 100.0 20000.0 0.25 0.0 0.0 0.0
    $# cmo con1 con2
    1.0 5 7
    $#lco or a1 a2 a3 v1 v2 v3
    0.0
    *DEFINE_BOX
    $# boxid xmn xmx ymn ymx zmn zmx
    1 -1.0 12.0 -1.0 1.0 -1.0 2.0
    *DEFINE_CURVE_TITLE
    Gravity
    $# lcid sidr sfa sfo offa offo dattyp lcint
    1 0 1.0 1.0 0.0 0.0 0 0
    $# a1 o1
    0.0 1.0
    100.0 1.0
    *DEFINE_CURVE_TITLE
    Piston Motion
    $# lcid sidr sfa sfo offa offo dattyp lcint
    2 0 0.6 0.0795775 0.0 0.0 0 0
    $# a1 o1
    0.0 0.0
    1.0 1.0
    2.0 0.0
    3.0 1.0
    4.0 0.0
    5.0 1.0
    6.0 0.0
    7.0 1.0
    8.0 0.0
    9.0 1.0
    10.0 0.0
    11.0 1.0
    12.0 0.0
    13.0 1.0
    14.0 0.0
    15.0 1.0
    16.0 0.0
    17.0 1.0
    18.0 0.0
    19.0 1.0
    20.0 0.0
    21.0 1.0
    22.0 0.0
    23.0 1.0
    24.0 0.0
    25.0 1.0
    26.0 0.0
    27.0 1.0
    28.0 0.0
    29.0 1.0
    30.0 0.0