Changes between Version 48 and Version 49 of doc/tec/bc

Timestamp:

Nov 19, 2018 10:26:35 AM (6 years ago)

Author:

suehring

Comment:

--

doc/tec/bc

@@ -309 +309 @@
 '''Method 2:''' In many cases detailed information about the Reynolds stress and turbulent length scales are not available, so that these information need to be parametrized. If no ASCII input file is provided in the input folder, this will be done automatically and the turbulence statistics at the inflow boundary will be estimated. 
 Please note, the derived turbulence statistics will depend on the height above ground but not on the horizontal location. Parametrization of the Reynolds stress follows [#rotach1996 Rotach et al. (1996)].
-An description of the applied turbulence parametrization will follow soon. 
+The diagonal components ''u,,11,,'', ''u,,22,,'', indicating the horizontal velocity variances, are estimated as follows:
+{{{
+#!Latex
+\begin{equation*}
+u_{i,i} = u_{*} ( 0.35\,(-\frac{z_i}{\kappa\,L})^\frac{2}{3}) + (5 - 4\,\frac{z}{z_i}, \: (i \in (1,2) )\,,
+\end{equation*}
+}}}
+with ''u'',,*,, being the friction velocity, ''k'' the von-Karman constant, ''L'' the Obukhov length, and ''z,,i,,'' the mean boundary-layer depth. 
+''u'',,*,, is estimated from the mean horizontal wind speed at the boundary at the first vertical grid point.
 
 At this point we emphasize that this method only generates turbulence which is statistically correlated. Large coherent structures such as e.g.  hexagonal pattern as typically observed in a convective boundary layer, however, cannot be generated by this method. So far, turbulence is only added to the three wind components. No perturbations are added to the subgrid-scale turbulent-kinetic energy and potential temperature.