Changes between Version 388 and Version 389 of doc/app/initialization_parameters

Timestamp:

May 25, 2018 8:40:17 AM (7 years ago)

Author:

sward

Comment:

--

doc/app/initialization_parameters

@@ -1986 +1986 @@
 }}}
 {{{#!td
-Factor for shift of cyclic conditions at the x-boundary in y-direction.\\\\
-In case of cyclic boundary conditions, a y-shift at the boundaries in x-direction can be introduced via parameter y_shift. The shift is done by modifying the processor grid in such a way that cores located at the right x-boundary communicate across it to processors with y-coordinate shifted by y_shift relative to their own. In this way, a shift by the size of one core's subdomain size in y-direction is realized.\\
-This feature has been implemented to counter the effect of streak structures in case of cyclic boundary conditions. For a description of these, see Munters (2016; http://www.dx.doi.org/10.1063/1.4941912).\\
-This feature can only be used with a multigrid pressure solver, as the data is not truly cyclic anymore. See [../inipar#psolver psolver]. 
+Shifts the left/right boundary by multiples of a subdomain size along y.\\
+Requires  [../inipar#bc_lr bc_lr] = 'cyclic',  [../inipar#bc_ns bc_ns] = 'cyclic' and [../inipar#psolver psolver] = 'multigrid'.\\\\
+This parameter introduces a shift by multiples of a subdomain size in y-direction at the left/right domain boundary. The shift is such that a point (coordinate y=yr) on the right domain boundary no longer corresponds with the point with the same y-coordinate on the left boundary, but instead with the point with the coordinate {{{y=yr+y_shift*(ny+1)/npey}}}. Conversely, a point on the left boundary with coordinate {{{y=yl}}} corresponds with the point on the right boundary with the coordinate {{{y=yl-y_shift*(ny+1)/npey}}}.\\
+Negative values and also those that exceed npey are allowed. They are transformed to the range {{{[0,npey-1]}}} internally.\\\\
+This feature has been implemented to alleviate the occurrence of streak-like structures that appear during simulations with neutral stratification, cyclic boundary conditions, and driving velocity with no v-component. For a description of these structures, see Munters (2016; ​http://www.dx.doi.org/10.1063/1.4941912).\\\\\\
+'''Schematic of the y_shift method:'''\\
+(Model domain with [../inipar#npex npex] = [../inipar#npey npey] = 5 and y_shift = 1)\\
+[[Image(y_shift_pic.png,260px)]]
 }}}
 |----------------