Changes between Version 27 and Version 28 of doc/tec/bc

Timestamp:

May 11, 2016 9:28:09 PM (9 years ago)

Author:

Giersch

Comment:

--

doc/tec/bc

@@ -328 +328 @@
 For non-cyclic lateral boundary conditions, the parameter [../../app/inipar/#psolver psolver] has to be set to '' 'multigrid' '' because the default FFT-solver can only be applied for cyclic boundary conditions.
 
-[[Image(grid_lr.png, 700px, border=1)]]
+[[Image(grid_lr.png, 600px, border=1)]]
 
 Figure 6: Grid structure at the lateral boundaries with non-cyclic lateral boundary conditions along the left-right direction. 
 
-[[Image(grid_ns.png, 700px, border=1)]]
+[[Image(grid_ns.png, 600px, border=1)]]
 
 Figure 7: Grid structure of the lateral boundaries with non-cyclic lateral boundary conditions along the north-south direction. 
@@ -425 +425 @@
 \end{align*}
 }}}
-In Orlanskis work, the phase velocity ''c'',,ψ,, was not averaged along the outflow, which is sufficient for simplified flows as shown by [#yoshida2010 Yoshida and Watanabe (2010)]. However, we found that in simulations of shear driven convective boundary layer with a strong wind component along the outflow, the approach of [#orlanski1976 Orlanski (1976)] was unstable. [#raymond1984 Raymond and Kuo (1984)] argued that locally calculated phase velocities leads to a large variation of phase speeds which can lead to numerical instabilities. Other works used a constant phase velocity or an average over the whole outflow area (see e.g. [#frölich2006 Fröhlich 2006, p.216) instead of the approach of [#orlanski1976 Orlanski (1976)]. With this in mind, we tested the average phase velocity calculated from the last mentioned equation, and the solution at the outflow becomes stable. We did not additionally average the phase velocity along the vertical direction, because the background wind usually varies with height. 
+In Orlanskis work, the phase velocity ''c'',,ψ,, was not averaged along the outflow, which is sufficient for simplified flows as shown by [#yoshida2010 Yoshida and Watanabe (2010)]. However, we found that in simulations of shear driven convective boundary layer with a strong wind component along the outflow, the approach of [#orlanski1976 Orlanski (1976)] was unstable. [#raymond1984 Raymond and Kuo (1984)] argued that locally calculated phase velocities leads to a large variation of phase speeds which can lead to numerical instabilities. Other works used a constant phase velocity or an average over the whole outflow area (see e.g. [#frölich2006 Fröhlich 2006, p.216]) instead of the approach of [#orlanski1976 Orlanski (1976)]. With this in mind, we tested the average phase velocity calculated from the last mentioned equation, and the solution at the outflow becomes stable. We did not additionally average the phase velocity along the vertical direction, because the background wind usually varies with height. 
 
 For the other flow directions, the indices of the above equations have to be replaced as follows: