125 lines
5.0 KiB
HTML
125 lines
5.0 KiB
HTML
<HTML>
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<CENTER><A HREF = "http://www.cfdem.com">LIGGGHTS WWW Site</A> - <A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LIGGGHTS Documentation</A> - <A HREF = "Section_commands.html#comm">LIGGGHTS Commands</A>
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<HR>
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<H3>fix particletemplate/multisphere command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>fix ID group-ID particletemplate/multisphere seed nspheres nspheresvalue keyword values ntry ntryvalue spheres values_spheres type mt opt_keyword opt_values
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
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<LI>particletemplate/multisphere = style name of this fix command
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<LI>seed = random number generator seed (integer value)
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<LI>nspheres = obligatory keyword
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<LI>nspheresvalue = number of spheres in the template (integer value):l
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zero or more keyword/value pairs can be appended
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<LI>keyword, values are documented in <A HREF = "fix_particletemplate_sphere.html">fix particletemplate/sphere</A> command
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<LI>ntry = obligatory keyword
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<LI>ntryvalue: number of tries for Monte Carlo approach
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<LI>spheres = obligatory keyword
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<LI>values_spheres = one out of the following options
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<PRE> option 1 = <I>file</I> <I>filename</I>
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option 2 = <I>file</I> <I>filename</I> <I>scale</I> <I>scalefactor</I>
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option 3 = <I>x1 y1 z1 r1 x2 y2 r2...</I> where x/y/z are sphere positions and r are the radii
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</PRE>
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<LI>type = obligatory keyword
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<LI>mt = multisphere type of the template
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<LI>opt_keyword = <I>mass</I> or <I>inertia_tensor</I>
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<PRE><I>mass</I> value = mass assigned to this particle template
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<I>inertia_tensor</I> values = Ixx Ixy Ixz Iyy Iyz Izz
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Ixx Ixy Ixz Iyy Iyz Izz = 6 independant components of the inertia tensor
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</PRE>
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>fix pts1 all particletemplate/multisphere 1 nspheres 3 atom_type 1 density constant 2500 ntry 1000000 spheres 0. 0. 0. 0.005 0.005 0. 0. 0.005 0.01 0. 0. 0.005
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fix pts2 all particletemplate/multisphere 1 nspheres 30 atom_type 1 density constant 2500 ntry 1000000 spheres file spherefile.txt
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</PRE>
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<P><B>LIGGGHTS vs. LAMMPS Info:</B>
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</P>
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<P>This command is not available in LAMMPS.
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</P>
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<P><B>Description:</B>
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</P>
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<P>Define a multisphere particle template that is used as input for a
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<A HREF = "fix_particledistribution_discrete.html">fix_particledistribution_discrete</A>
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command. The particle parameters (positions, radii) are either defined
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manually as arguments to this command or via a text file, via the keyword
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<I>file</I>. The format of this text file is
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</P>
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<PRE>x1 y1 z1 r1
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x2 y2 z2 r2
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...
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</PRE>
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<P>and the number of lines in this file has to be equal to n_spheres as
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defined in this command. Comments can be made in this file via the '#'
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character. Optionally, when a file is used for defining the multi-sphere
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template, keyword <I>scale</I> can be used to define a <I>scalefactor</I> to scale
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up or down the particle positions and radii.
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</P>
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<P>After the spheres are read, a Monte Carlo procedure is used to assess
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everything that is needed for the motion integration: mass, center of mass,
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and the inertia tensor including its eigensystem.
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</P>
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<P>As an alternative, the body's mass and inertia tensor can be specified
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directly via keywords <I>mass</I> and <I>inertia_tensor</I>. Note that you can
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use these keywords only together, i.e. defining only <I>mass</I> but not
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<I>inertia_tensor</I> will throw an error.
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</P>
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<P>The multisphere type or shape type as defined via the <I>type</I> keyword must
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be unique integer given to each fix particletemplate/multisphere
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command by the user (starting with 1), the list of all multisphere types
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in the simulation must be consecutive. At the moment, the multisphere type
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is not used, but will be used to implement orientation-dependant drag
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for CFD-DEM simulations in the future.
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</P>
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<P>IMPORTANT NOTE: As opposed to the number-based distributions used by
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<A HREF = "fix_pour_legacy.html">fix_pour_legacy</A>, this fix uses the more common
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distribution based on mass-% for the radius distribution (as does
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<A HREF = "fix_particledistribution_discrete.html">fix_particledistribution_discrete</A>).
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</P>
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<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
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</P>
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<P>Information about the random state in this fix is written to
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<A HREF = "restart.html">binary restart files</A> so you can restart a simulation with
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the same particles being chosen for insertion. None of the
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<A HREF = "fix_modify.html">fix_modify</A> options are relevant to this fix. No global
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scalar or vector or per-atom quantities are stored by this fix for access
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by various <A HREF = "Section_howto.html#4_15">output commands</A>. No parameter of this
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fix can be used with the <I>start</I>/<I>stop</I> keywords of the <A HREF = "run.html">run</A>
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command. This fix is not invoked during <A HREF = "minimize.html">energy minimization</A>.
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</P>
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<P><B>Restrictions:</B> none
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "fix_particletemplate_sphere.html">fix_particletemplate_sphere</A>
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</P>
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<P><B>Default:</B> radius = 1.0, density = 1.0, atom_type = 1
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</P>
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</HTML>
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