Changes between Version 69 and Version 70 of doc/tec/bc

Timestamp:

Sep 13, 2021 10:35:08 AM (4 years ago)

Author:

suehring

Comment:

--

doc/tec/bc

@@ -563 +563 @@
 \end{equation*}
 }}}
-In order to allow for a dynamic adjustment of the strength of the imposed turbulence, the Reynolds stress tensor is update at regular intervals that can be adjusted individually. In other words, the turbulence generator considers for changing atmospheric stability in case of a multi-day simulation.
-
-Too date, no proper parametrization of turbulent length scales that works for all stability regimes and within the entire boundary layer is available. 
-Hence, for the moment the integral length scales are set to
- {{{
-#!Latex
-\begin{equation*}
-l_{i,j} = 8 \cdot MIN( \Delta x_i ), \: i \in (1,2,3)\,,
-\end{equation*}
-}}}
-which arises from following considerations: On the one hand, from the numerical point of view the imposed perturbations should not be rapidly eliminated by the numerics. 
-The numerical dissipation and dispersion, however, act on scales up to 8 times the grid spacing (5th order scheme, see: wiki:/doc/tec/discret]), meaning that scales < 8 times the grid spacing are rapidly dispersed and dissipated due to numerical errors. In order to trigger further turbulence development within the model domain, the imposed correlated turbulence should be on scales larger than the numerically-affected scales. 
-On the other hand, however, imposing too large length scales could trigger structures that exist throughout the entire model domain, particularly under stable conditions, which in turn could bias the simulation results. 
-Hence, as a compromise, length scales are set to 8 times the minimum grid spacing. 
-
-Note, for ''z''>''z,,i,,'' the components of the stress tensor, length- and timescales are set to zero so that effectively no synthetic turbulence is imposed above the boundary-layer height (also saving computational costs).  //
- 
-'''Please note, method 2 currently undergoes extensively testing.'''
+In order to allow for a dynamic adjustment of the strength of the imposed turbulence, the Reynolds stress tensor is update at regular intervals that can be adjusted individually. In other words, the turbulence generator considers for changing atmospheric stability in case of a multi-day simulation. For further information about this approach we refer to [https://doi.org/10.5194/gmd-14-5435-2021 Kadasch et al. (2021)].
 
 At this point we emphasize that using the turbulence generator from [#xie2008 Xie and Castro (2008)] only generates turbulence which is correlated in space and time but not necessarily generate realistic turbulent structures. Large coherent structures like e.g. hexagonal pattern as typically observed in a convective boundary layer, however, cannot be generated by this method. 
 Further, we want to add that turbulence is only added to the three wind components. No perturbations are added to the subgrid-scale turbulent-kinetic energy and potential temperature.
 
-If switched on, the turbulence generator imposed turbulent fluctuations on all lateral boundaries with Dirichlet boundary conditions for the velocity components. For example, if the offline nesting is switched on, where all four lateral boundaries are non-cyclic, the turbulence generator applied at all lateral boundaries, even though a lateral boundary is also an outflow boundary layer. 
-
 == References ==
 * [=#holtslag] '''Holtslag AAM, Bruin HARD.''' 1988. Applied modelling of the night-time surface energy balance over land. J. Appl. Meteorol. 27: 689–704.
@@ -600 +581 @@
 * [=#lund1998] '''Lund TS, Wu X, Squires KD.''' 1998. Generation of turbulent inflow data for spatially-developing boundary layer simulations. J. Comput. Phys. 140: 233–258.
 
+
+* [=#kadasch2021] '''Kadasch E, Sühring M, Gronemeier T, Raasch S.''' 2021. Mesoscale nesting interface of the PALM model system 6.0. Geosci. Model Dev., 14: 5435–5465.
+
 * [=#kataoka2002] '''Kataoka H, Mizuno M.''' 2002. Numerical flow computation around aerolastic 3d square
   cylinder using inflow turbulence. Wind Struct. 5: 379–392.