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doc/src/fix_wall_stochastic.txt

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+"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
+
+:link(lws,http://lammps.sandia.gov) link(ld,Manual.html)
+:link(lc,Section_commands.html#comm)
+
+:line
+
+fix wall/stochastic command :h3
+
+[Syntax:]
+
+fix ID group-ID wall/stochastic reflectionstyle face pos temp velx vely velz accomx accomy accomz ... :pre
+
+ID, group-ID are documented in "fix"_fix.html command :ulb,l
+
+wall/stochastic = style name of this fix command :l
+
+one or more face/arg pairs may be appended :l
+
+reflectionstyle = diffusive or maxwell or cercignanilampis
+
+face = {xlo} or {xhi} or {ylo} or {yhi} or {zlo} or {zhi} :l
+
+  {xlo},{ylo},{zlo} pos = EDGE or constant 
+
+    EDGE = current lo edge of simulation box
+
+    constant = number like 0.0 or -30.0 (distance units)
+
+    temp = wall temperature
+
+    velx, vely, velz = wall velocity along x, y, z directions
+
+    accomx, accomy, accomz = accommodation coefficients along x, y, z directions (only for maxwell and cercignanilampis reflection style)
+
+  {xhi},{yhi},{zhi} pos = EDGE or constant or variable
+
+    EDGE = current hi edge of simulation box
+
+    constant = number like 50.0 or 100.3 (distance units)
+
+    temp = wall temperature 
+
+    velx, vely, velz = wall velocity along x, y, z directions
+
+    accomx, accomy, accomz = accommodation coefficients along x, y, z directions (only for maxwell and cercignanilampis style)
+
+    :pre
+
+zero or more keyword/value pairs may be appended :l keyword = {units} :l {units}
+value = {lattice} or {box}
+
+    {lattice} = the wall position is defined in lattice units
+
+    {box} = the wall position is defined in simulation box units :pre
+
+:ule
+
+[Examples:]
+
+fix zwalls all wall/stochastic diffusive zlo EDGE 300 0.1 0.1 0 zhi EDGE 200 0.1 0.1 0
+
+fix ywalls all wall/stochastic maxwell ylo 5.0 300 0.1 0.0 0.0 0.8 yhi 10.0 300 0.1 0.0 0.0 0.8
+
+fix xwalls all wall/stochastic cercignanilampis xlo 0.0 300 0.0 0.1 0.9 0.8 0.7 xhi EDGE 300 0.0 0.1 0 0.9 0.8 0.7 units box :pre
+
+[Description:]
+
+Different from the command fix wall/reflect which is equivalent to the mirror reflection, the post collision velocity of the atoms in the stochastic wall is random. The randomness can come from many sources: thermal motion of solid atoms, the surface roughness, etc... Three stochastic wall models are implemented. 
+
+Diffusive wall (reflectionstyle = diffusive): all the gas atoms are reflected diffusively. Their velocity distribution corresponds to the equilibrium distribution at the wall temperature. 
+
+Maxwell model (reflectionstyle = maxwell): the reflection is partially diffusive and partially specular. The accommodation coefficient is the portion of the diffusive reflection "Maxwell"_#Maxwell. 
+
+Cercignani Lampis model: 3 accommodations coefficients are used, two velocity accommodation coefficients and one normal kinetic energy accommodation "CL"_#CL, "To"_#To. The code will recognize automatically the normal direction of the wall and the other two tangential directions. For example, if accomx = 0.5, accomy = 0.2, accomz = 0.3 and the wall is normal to direction y, accomx and accomz are the tangential velocity accommodation coefficients and accomy is the normal kinetic energy accommodation coefficients.
+
+The {units} keyword determines the distance units used to define a wall position
+
+A {box} value selects standard distance units as defined by the
+"units"_units.html command, e.g. Angstroms for units = real or metal. 
+
+A {lattice} value means the distance units are in lattice spacings. The
+"lattice"_lattice.html command must have been previously used to define the
+lattice spacings.
+
+:line
+
+[Restrictions:]
+
+Due to the similarities, this fix has the same limitation as the the
+wall/reflect. Any dimension (xyz) that has a wall must be non-periodic. It
+shoudld not be used with rigid bodies such as those defined by a "fix rigid"
+command. Furthermore, the wall velocity must lie on the same plane as the wall. Package USER-MISC is required to use this fix.
+
+[Related commands:]
+
+"fix wall/reflect"_fix_wall_reflect.html, 
+ 
+[Default:] none
+
+:line
+:link(Maxwell)  [(Maxwell)] J. C. Maxwell. Philos. Trans. Royal Soc. London. 157: 49–88 (1867).
+
+:link(CL)  [(CL)] C. Cercignani and M. Lampis. Transp. Theory Stat. Phys. 1, 2, 101 (1971).  
+
+:link(To)  [(To)] Q.D. To, V.H. Vu, G. Lauriat, and C. Leonard. J. Math. Phys. 56, 103101 (2015).
+

doc/src/lammps.book

@@ -404,18 +404,16 @@ fix_vector.html
 fix_viscosity.html
 fix_viscous.html
 fix_wall.html
-fix_wall_cl.html
 fix_wall_body_polygon.html
 fix_wall_body_polyhedron.html
-fix_wall_diffusive.html
 fix_wall_ees.html
 fix_wall_gran.html
 fix_wall_gran_region.html
-fix_wall_maxwell.html
 fix_wall_piston.html
 fix_wall_reflect.html
 fix_wall_region.html
 fix_wall_srd.html
+fix_wall_stochastic.html
 
 lammps_commands_compute.html
 compute.html
@@ -572,6 +570,7 @@ pair_charmm.html
 pair_class2.html
 pair_colloid.html
 pair_comb.html
+pair_cosine_squared.html
 pair_coul.html
 pair_coul_diel.html
 pair_coul_shield.html