133 lines
5.6 KiB
HTML
133 lines
5.6 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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</CENTER>
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<HR>
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<H3>fix massflow/mesh 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 massflow/mesh mesh mesh-ID vec_side vx vy vz keyword value ...
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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>massflow/mesh = style name of this fix command
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<LI>mesh = obligatory keyword
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<LI>mesh-ID = ID of a <A HREF = "fix_mesh_surface.html">fix mesh/surface</A> command
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<LI>vec_side = obligatory keyword
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<LI>vx, vy, vz = vector components defining the "outside" of the mesh
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<LI>zero or more keyword/value pairs may be appended to args
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<LI>keywords = <I>count</I> or <I>point_at_outlet</I> or <I>append</I> or <I>file</I> or <I>screen</I> or <I>delete_atoms</I>
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<PRE> <I>count</I> value = <I>once</I> or <I>multiple</I>
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once = count particles only once
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multiple = allow particles to be counted multiple times
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<I>point_at_outlet</I> pointX pointY pointZ
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pointX pointY pointZ = coordinates of point on the outlet side of the surface
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<I>inside_out</I>
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use this in connection with <I>point_at_outlet</I> to flip direction particle counting
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<I>file</I> value = filename
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<I>append</I> value = filename
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filename = name of the file to print diameter, position and velocity values of the particles
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<I>screen</I> value = <I>yes</I> or <I>no</I>
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<I>delete_atoms</I> value = <I>yes</I> or <I>no</I>
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yes = to remove the particles that pass through the mesh surface
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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 mass all massflow/mesh mesh inface vec_side 0. 0. -1.
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</PRE>
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<PRE>fix mass all massflow/mesh mesh inface count once point_at_outlet 0. 0. 0.
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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 LIGGGHTS 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>Fix massflow/mesh tracks how many particles penetrate through a mesh surface,
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as defined by a <A HREF = "fix_mesh_surface.html">fix mesh/surface</A> command.
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It counts the total number of particles and the associated mass. Only particles
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part of <I>group</I> are eligible for counting.
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</P>
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<P>Particles are counted if they cross from the inner side of the mesh to the outer
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side of the mesh. The outer side can be defined by using the keyword <I>vec_side</I>,
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by specifying a point at the outlet side of the mesh (keyword <I>point_at_outlet</I>). Note
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that the vector defined by <I>vec_side</I> does not necessarily have to be
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perpendicular to the mesh face.
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</P>
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<P>The following restrictions apply in case <I>vec_side</I> is specified: (i) the
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<A HREF = "fix_mesh_surface.html">fix mesh/surface</A> has to be planar, and (ii) the vector
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defined by <I>vec_side</I> may not lie inside the mesh plane.
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</P>
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<P>The following restriction applies in case <I>point_at_outlet</I> is used: the <I>count</I>
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value has to be set to once.
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</P>
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<P>The keyword <I>point_at_outlet</I> is especially useful in case a cylindrically-shaped
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surface is used. The <I>point_at_outlet</I> value should be on the cylinder axis in
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this case. If you like to track particles moving away from the cylinder axis,
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specify the <I>point_at_outlet</I> on the axis, and use the keyword
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<I>inside_out</I> to flip the direction.
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</P>
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<P>When <I>count</I> = once, then each particle is only counted once, for <I>count</I> = multiple
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a particle contributes to number and mass count each time it crosses the mesh face.
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This can happen e.g. in the case of periodic boundary conditions or in re-circulating
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flow conditions.
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</P>
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<P>The diameter, position and velocity of the particles can be written into a file using the <I>file</I> keyword,
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by specifying a filename.
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</P>
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<P>If the <I>screen</I> keyword is used, output by this fix to the screen and
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logfile can be turned on or off as desired.
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</P>
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<P>If the <I>delete_atoms</I> keyword is used then the particles passing through the mesh
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surface are deleted at the next re-neighboring step.
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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 this fix is written to <A HREF = "restart.html">binary restart files</A> .
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</P>
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<P>This fix computes a per-atom vector (the marker) which can be accessed by
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various <A HREF = "Section_howto.html#howto_15">output commands</A>. The per-atom vector
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(i.e., the marker) can be accessed by dumps by using "f_massflow_ID", .
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This fix also computes a global vector of length 6. This vector can be
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accessed via "f_ID", where ID is the fix id. The first vector component
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is equal to the total mass which has crossed the mesh surface, the second vector
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component indicates the particle count. The third vector component
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is equal to the total mass which has crossed the mesh surface since the last output
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divived by the time since the last output (i.e., the mass flow rate), the fourth vector
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component indicates the particle count since the last output divived by the time
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since the last output (i.e., the number rate of particles). The fifth and sixth vector
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components are the deleted mass and the number of deleted particles. This vector
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can also be accessed by various <A HREF = "Section_howto.html#howto_15">output commands</A>.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>Currently, this feature does not support multi-sphere particles.
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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 = "compute_nparticles_tracer_region.html">compute nparticles/tracer/region</A>
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</P>
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<P><B>Default:</B>
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</P>
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<P><I>count</I> = multiple, <I>inside_out</I> =false, <I>delete_atoms</I> = false
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</P>
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</HTML>
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